Kevin Hall (5:49)

My pleasure.

Rich Roll (5:50)

I consider you a very important figure here in the world of nutrition science. You're an honest actor, a good faith actor, always trying to basically set matters to rights amidst a hurricane of nutritional misinformation out there. And I really appreciate your voice and for you taking the time to talk to me today, that means a lot.

Kevin Hall (6:12)

Thanks so much.

Rich Roll (6:13)

Some of the audience might be familiar with your name because there was a little bit of a political standoff or kerfuffle several months ago between you and HHS and RFK Jr. Which resulted in you resigning after 21 years at the NIH. And that created a bit of a media circus. I do want to know about that, but we're not going to start with that. As somebody who has been studying metabolism for decades, top level, what are the conclusions that you've, that you've drawn from the randomized controlled trials that you've performed about the relationship between metabolism, weight gain and weight loss?

Kevin Hall (6:55)

Yeah. So when people are losing weight and they are decreasing their body size, either by, you know, an exercise intervention, a diet intervention, a pharmacotherapy or something like that, they tend to at rest. Their resting metabolism when they're not moving is decreasing. Now it seems to decrease even more than you'd expect, at least transiently, while they're in active weight loss compared to what you'd expect for their decreasing body size. Larger people burn more calories than smaller people. So it goes to figure that as you become smaller, you burn fewer calories. But it turns out in the process of becoming smaller, during that period when you're actively losing weight, it seems like metabolism slows even more than expected. This is something called metabolic adaptation. One of the most extreme cases of this was seen in volunteers in Minnesota who volunteered for a starvation experiment by Ancel Keys back during World War II. The idea was they volunteered to serve their country. They were conscientious objectors, and they basically said, we're going to starve because eventually the war is going to end and we need to learn how to refeed all these people in Europe who've been subject to starvation during the war. And so these folks basically were relatively lean to begin with. And 36 people underwent like a 50% calorie restriction, and you could just see their resting metabolic rate falling, and it went down much more than you'd expect based on how much weight that they lost. A similar sort of thing was observed by us when we examined these folks in this Biggest Loser television competition. We saw that while these folks were doing insane amounts of exercise and cutting their calories in their diets, their metabolic rate was slowing by a huge amount as well during this program, and it.

Rich Roll (8:43)

Stayed slow long after.

Kevin Hall (8:45)

Yeah, and that's something that's still a little bit mysterious, to be honest with you, because unlike the Minnesota experiment folks who they did have their refeeding phase and they did regain some of their lost weight, their metabolic rate improved. It actually went back up towards normal. And most sort of weight loss trials that have looked at people, and unfortunately, many people who lose weight via lifestyle intervention and regaining some of the lost weight, those folks tend to recover their resting metabolic rate as well. There's something really weird about what happened in the Biggest Loser study, and we have some theories about what that might be. It might be that there's something about the fact that these folks actually started off very sedentary. They became very extraordinarily physically active during the program, exercising three hours every day, seven days a week, vigorously. And then even when they went home during the weight loss competition was an hour a day of vigorous activity. Even six years later, they were pretty darn active compared to where they started. So is there some trade off going on between if you become that physically active, does something else in metabolism slow down to compensate? That's a theory. At this point, we don't really have good data, and unfortunately, it's a hard experiment to repeat. Right. Unfortunately, the television show's canceled, so I can't just go back and do that because it was a bit of a train wreck for a television show, to be honest. But, yeah, something interesting was going on there that I don't think we fully understand.

Rich Roll (10:16)

Yeah. So correct me if I'm wrong, but essentially with this Biggest Loser study, the conventional wisdom, or the expectation was that metabolic rate was gonna correlate pretty tightly with people who regained the weight. There would be a correlation between metabolic rate and the people who regain the weight and the people who are able to maintain their new lower weight. Correct. And the results actually defied that on some level.

Kevin Hall (10:42)

Yeah. So there were several things that were surprising about the results. One was that you would think that the more you slowed your metabolism, the less you'd be able to lose, the less weight you'd be able to lose. Because after all, that's kind of physics, right? If you were burning more calories and you cut the same number of calories in your diet, then you would expect to lose more weight. Like, the energy has to come from somewhere. It's going to come from body fat. What we observed in the Biggest Loser was that the people who were most successful at losing weight during this kind of crazy competition, they were the ones who experienced the most slowing of metabolism. So that was kind of weird. It was like, okay, what's going on there? Why? It seemed to be completely. The expected correlation was flipped. And then there is this idea that the slowing of metabolism, well, that's gotta be a bad thing. That's gotta predict who's gonna regain the most weight after this crazy competition. And there turned out to be no significant relations whatsoever with who regained the most weight. It wasn't the folks who had the greatest slowing. It wasn't the folks who had the least amount of slowing. It was more or less random. And then at six years later, the ones who were most successful at keeping the weight off continue to have the greatest slowing of metabolism. And the only way I've been able to sort of make sense of that is that our changes in metabolism and the slowing of metabolism is a response to the intervention. It's not determinative. The way I sort of like to think about it is it's kind of like the tension on a spring. And if you're doing an intervention to stretch the string, the spring, and thereby kind of cause weight loss, you can do that, but the greater pullback you'll feel. Right? But the greater you pull, the more weight you've lost. So the distance that you pulled the spring is in some sense related. It's like how much weight you're losing. But the more you pull, the more the resistance, the greater the tension on the spring. That's the metabolic slowing. Clearly, if the spring had less tension, you'd be able to pull it further. Right. But the point is, it's not determinative how long the spring is. It's how hard you're pulling on the darn thing, Right? So whatever lifestyle intervention these folks were able to do, both on the television program as well as after they went home, that's gonna be determinative of how much weight they've been able to keep off. And the slowing of metabolism, while not helpful, it's really an indication. It's kind of like the cart, not the horse, Right? It's the follower, and it's the response to that intervention on Some level, it.

Rich Roll (13:12)

Makes sense that somebody who is attempting to lose weight and perhaps even a dramatic amount of weight, that physiologically the body would respond by slowing metabolism because it will interpret that as a threat. We gotta hold onto this weight. This guy's trying to starve us. Let's keep this fat here because we might need it as a sort of evolutionary adaptation.

Kevin Hall (13:34)

Yeah, I think that that makes sense if you're lean. Right. But once you kind of cross a certain threshold, how long do you really have to prepare for starvation? Most people. So humans are apes that actually store quite a bit of body fat compared to other apes. Like even lean humans have quite a bit of body fat. We talk in the book about most people have enough body fat on them to last for months. Starvation periods that last for longer than months. Most people are not dying of losing body fat. They're dying of the infections and the propensity for infections that come along with that. And it's not clear if body fat is protective of that or not. So I sort of expected that maybe we wouldn't see this if we were studying people with obesity because they're way above the necessary requirements.

Rich Roll (14:27)

No alarm bells need to go off.

Kevin Hall (14:28)

Exactly. But it seems like it's the same alarm bells. And how that works is really interesting to me. Right. I expected clearly the Minnesota starvation folks who were like 67kg on average, so pretty lean by today's standards. Yeah. And when they're losing weight, they're losing mostly lean body mass. They're not losing as much body fat because they start off with very little amounts of body fat. So clearly that's a case where, gosh, yeah, the alarm bell should go off. You should slow down metabolism a lot, but you're starting off with a lot of stored energy. It's kind of like it'd be like your phone going into power saving mode, even though it was at 98% energy. Right. You only really think that that should kick in after you get 10%. Right. But it seems like for whatever reason, people with obesity seem to have the same sorts of responses to that acute challenge that is causing a calorie deficit and whatever that is. You're right. They sort of respond to that challenge by saying, yep, no, we're slowing things down. We're going into power saving mode. And I don't think we fully understand all of the mechanisms by which that happens. Some of it has to do with the sympathetic nervous system and slowing of that. But, yeah, I don't think we fully understand.

Rich Roll (15:42)

Yeah, I mean, what is your sense of where the answer lies. Like, is it in genetics? Is it in the microbiome? Is it in the hormonal system?

Kevin Hall (15:50)

Yeah, I mean, my sense is that it's probably mostly in the hormonal system. One of the things that we found was that the relationship between the slowing of metabolism was related to how much the hormone leptin changed. And leptin, even though it's in a person who's kind of just maintaining their weight, it's proportional to how much body fat that they have. When you take a person, even with obesity, who starts off with a very high amount of leptin, and even though they haven't lost very much body fat yet, and you put them into this energy deficit, leptin levels crash. So it seems like that metabolic slowing is not sensitive necessarily to the absolute amount of leptin that's there, but the change in the decrease that takes place. That's a hypothesis. I don't think we have a good experimental investigation of that yet. There's folks like Rudy Leibel and Michael Rosenbaum have done some experiments where they actually kind of try to infuse leptin at different levels to try to prevent that. And they've seen that it seems to be successful at preventing the reduction in energy expenditure, especially at low levels of physical activity, where a good chunk of our energy budget goes to. So those are kind of interesting experiments that suggest that that might be the case. But again, I don't think that they're completely determinative either.

Rich Roll (17:03)

And what do your findings suggest about the malleability of our metabolic rate? Like, how much agency do we have? Like, oh, okay, my metabolism is slow. Like, what can I do? I'm going to kickstart it. I'm going to hyp. Drive it. Can we insert ourselves into this equation to drive a certain outcome here?

Kevin Hall (17:23)

I mean, there's lots of promises, right? There's lots of promises that certain supplements can increase metabolism. And the evidence behind those is, well, yeah, maybe you can detect a statistically significant change in metabolism, exposing yourself to large amounts of these kinds of supplements. But it's pretty clinically meaningless. The times that we've actually. The only time we've actually come up with really good ways of speeding up people's metabolism. This was again, in the sort of turn of the 20th century. There was a compound that was discovered in a munitions factory during World War I where people were spontaneously losing weight. And we were like, what's going on? It turns out that they were exposed to something called dinitrophenol. Which turns out to be an uncoupler of mitochondria. So it actually prevents the mitochondria from functioning properly, not making as much ATP as they should, and as a result, metabolism. Exactly. And it turned out to be extremely effective for weight loss, but also incredibly dangerous. In fact, one of the first things that the newly formed FDA did was withdraw dinitrophenol from medications that were allowable for use. Because it was so dangerous, many people were dying. And it's actually not very encouraging to see that there are still some bodybuilders out there that are kind of obtaining dinitrophenol for cutting for competitions and things like that. It's still available, but yeah, it's not safe.

Rich Roll (18:59)

What about exercise and. Or nutrition timing? What is the difference between grazing lightly throughout the day versus, you know, an intermittent fast? You know, it would seem to me that these things would, you know, both of these things would have a significant impact on metabolism, would they not?

Kevin Hall (19:18)

So I think we have to separate out some of the things that we talk about in terms of like resting metabolism. That's kind of things that you're doing when you're not eating anything and you're not moving around, which is one of the things. That's what we were primarily measuring in the Biggest Losers. And when we were talking about metabolic slowing, that's what Ancel Keys was. Is talking about in the Minnesota Starvation, folks. The kind of sort of basal metabolic rate. Yeah, if there is an effect of exercise and those things, it tends to wash away after like there's a period like hours, many hours after exercise, where it seems like there is some residual response, but that seems to go away. But the exercise, you'll go back to.

Rich Roll (19:54)

That same basal rate.

Kevin Hall (19:56)

Yeah, yeah, but there is a period like if. Yeah. After you feel like you've calmed down from your exercise. If I was to measure your resting metabolic rate, it would indeed be higher. But we're not talking for days, we're talking hours after exercise. But of course there's the energy expenditure of exercise. Right. Which is also part of the total calories that you're burning. And obviously that goes up. There's some controversy about how much compensation in other aspects of your physical activity, like if you go for a run, do you not fidget as much afterwards or something like that? What degree of compensation is there? And then there's even compensation that could be potentially theorized. That may have been what we saw in the Biggest Loser folks. Right. Had now appreciably increased their physical activity, energy expenditure Is that one of the reasons why we saw the reduction in resting metabolic rate? It was certainly those two things were correlated with each other. But again, I don't think that we have good evidence of that. But that is one obvious thing that you can do to increase your overall calorie expenditure is to increase your physical activity. To what degree some people compensate for that with other parts of their energy budget, I think is something that there's some debate about right now.

Rich Roll (21:08)

And you can't decouple that from increases, increases in appetite as a consequence of more exercise or whatever kind of diet you're on that might have that whiplash effect on appetite increase later.

Kevin Hall (21:22)

Right. And I mean, in fact, it's really interesting that there is this coupling, right. Because we do regulate our body weight and appetite and expenditure are these coupled processes that somehow influence each other. There's a lot of talk about cold plunges or actually spending a lot of time in cold water and things like that. That interestingly, the few studies that have done cold exposure in these kind of respiratory chambers where we can measure oxygen consumption, carbon dioxide production, those folks, yes, they have an increase in calorie expenditure. Some of it is from shivering, some of it is from brown adipose tissue that's brown fat that's specifically evolved to kind of heat us up. It's more prevalent in leaner people and less prevalent in people with obesity. Certainly younger people, more young people have it than the most that you'll ever have as a baby. But it turns out that when you do those kinds of exposures and you can increase the total number of calories that people are burning and you let them eat whatever they want, they actually overeat the calories so that they will happily compensate for those increased calories from expenditure.

Rich Roll (22:31)

The caloric expenditure in that context is pretty de minimis though also.

Kevin Hall (22:35)

Yeah, it depends how you do it. Right. I mean if you actually induce shivering, it can be pretty darn high. I mean it's not a comfortable feeling by any stretch of the imagination. So there's like people, people do studies where they kind of try to ramp up the temperature slowly and try to get you into a range where you're experiencing the non shivering thermogenesis. And yeah, that tends to be pretty minimal. But once you get to the shivering mode, yeah, your energy expenditure goes up quite a lot.

Rich Roll (23:02)

Interesting.

Kevin Hall (23:02)

So yes, also turns out to be pretty darn uncomfortable to do that for a meaningful period of time. Sure. Short period of time. And yeah, you look at the rate of energy expenditure is very high but you're only doing it for a short period of time. So it's not really a kind of a weight loss tool because over the course of the day, while there's many, many more hours of the day, you can compensate it for it by eating more. You can compensate for it by changing other parts of your energy budget. So it's not exactly clear, but I think that one of the ways that I thought was most interesting to kind of look at this coupling between calorie output and appetite was a study that my colleagues did when they were testing a new type 2 diabetes drug that essentially works on the kidneys and increases outp of glucose. And they did this placebo controlled trial in people with type 2 diabetes. And they're able to kind of have folks, many hundreds of calories are being spilled in the urine of these folks. And of course they don't know it unless they're tasting their urine. It's getting sweeter. I don't think that's a common phenomenon. So there's placebo group and these folks that are randomized to this drug that's spilling excess calories in the urine. And if you actually look to see what happens, yeah, they lose weight, but they don't lose anywhere near as much weight as you would expect just based on the calories that were spilled in their urine. And so we did some work with the folks at this drug company to figure out, well, how much were they actually compensating for? We're not talking about days, we're talking about happening over months. Over the course of a year, they eventually almost completely compensate for the lost calories by increasing their calorie intake above baseline by several hundred calories per day so that they plateau at a lower weight, but it's only about 4 or 5 kg lower than they were to begin with. If they just kept eating the same amount, they would have lost triple that amount of weight.

Rich Roll (24:54)

Yeah. So what do you make of that?

Kevin Hall (24:56)

So it tells me that there's some coupling between calorie expenditure or loss of calories from the body in terms of either you're peeing them out or you're expending them through physical activity or exercise or resting metabolic rate. And the weight change that is occurring is somehow a feedback system to the brain to very gradually and subtly over many, many days and months, shift upwards the number of calories that people are eating. And we tried to quantify that and relate it to what's the degree of overall calorie slowdown that people experience when they lose Weight. And it turns out to be a much stronger effect than the slowdown of calorie expenditure. So if you kind of quantify it, for every kilogram of weight that you lose, your calorie expenditure goes down by about 25 calories per day. So you lose 10 kilos, 22 pounds, you'll be burning about 250 calories per day lower than you were before. You've lost that weight. Appetite seems to go up by about 95 calories per day, so it's going to outpace that. Yeah. And so the plateaus in weight that we see when people kind of experience that in concert with a lifestyle change, for example, you cut calories in people's diets, part of that plateau is because of the metabolic slowing, the smaller body burning fewer calories. But the vast majority of it is because appetite has gone up to compensate. And people don't report that. Right. They actually don't report their food intake increasing. Like if you ask them to kind of do a 24 hour recall of what are you eating in the first month of your diet versus at 12 months after you've stopped losing weight weight, those numbers are actually quite similar. But by all objective measures, their calorie intake has climbed substantially. Maybe not quite up to baseline, but it's climbed substantially. And the way I like to think about it is that these folks are reporting not their absolute number of calories, they're reporting how hard they're still working to maintain that lifestyle intervention and that degree of effort that they're putting in. And I think that is probably pretty consistent. It's just that they're fighting a greater and greater battle. The more weight that they lose. They're basically, the weight loss per se is causing their appetite to increase, it's causing their energy expenditure to go down. And despite that constant effort that they're putting in, they finally equalize. The biology has equalized whatever the effort was that they put in. And so now weight plateaus. And I think many people get the experience of, well, what the heck am I putting in all this effort for?

Rich Roll (27:33)

Yeah, I mean, we're painting sort of a of bunch, bleak, disempowering picture here. It's almost as if the body has this homeostatic set point and no matter what we do to try to find a workaround, it has a crafty way of making sure that it returns to that homeostatic point, but doesn't fully return.

Kevin Hall (27:53)

I think that's the point is that people will lose weight and they'll keep it off as Long as they continue that level of effort. Now, whether or not they're satisfied with that amount of weight loss, whether or not it's meaningful for them from a psychological perspective, whether or not it's enough weight loss to be clinically meaningful, I think those are all important questions. And whether or not that that actually effort feels effortful anymore in terms of have they been able to kind of engage in habits and work those lifestyle changes into their overall lifestyle in a way that they can find sustainable. And that's been like, the key trick is that every New Year's people talk about losing weight. And I always say, well, well, whatever you're going to do, make sure that you can keep that as part of your life, because otherwise, as soon as you stop doing it, the weight is probably going to increase. And so, yeah, you're right. If people are white knuckling it and saying, I'm just going to do this and it's a temporary thing and I'm going to get to my goal weight and then I can relax, it's like, yeah, that's not the way it works.

Rich Roll (28:58)

We all know how that goes.

Kevin Hall (28:59)

Yeah, right.

Rich Roll (29:06)

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Kevin Hall (32:08)

Yeah. So I think different people mean different things when they say calories in, calories out. And it's helpful to kind of know what are we talking about when we say this. So, for example, there are some folks who say the only thing that matters when it comes to body fat loss. So we have to focus on what is the outcome that we're interested in is the discrepancy between calorie intake and calorie expenditure. And that's an interesting question. And it's not necessarily the case that that would be. So in other words, if you could change the type of calories. So the calories we're talking about in food are the calories that you get from oxidizing one of the three macronutrients or a multiple mixture of macronutrients, carbohydrate, fat and protein. And it could be that calorie expenditure depends very sensitively on what mixture of nutrients you are provided with. Right. And when people were first studying this in dogs back in the 19th century, what they were doing was very interesting experiments where they were doing all these respiratory measurements in dogs. They were starving them at first to see how much body fat they would lose and then they'd give them back like sugar the only thing that the dog gets is sugar. And they calculate how much did body fat loss slow, and they give them back fat, pure fat, pure sugar. And it turned out there was very different amounts of fat and sugar that were required to equally slow the loss of fat in a starving dog. And this was a mystery for a long time. It's like, why is it that you had to give more than double the amount of sugar to stop fat loss slowing as fat? And it wasn't until this guy named Max Rubner decided to start to think about things in terms of, well, how many calories are in sugar and fat. And so per unit mass, it turns out that the sugar has less than half the calories of fat. And it turned out that the loss of body fat in the dog wasn't matching how many grams of sugar or fat you were giving. It turned out how many calories of sugar or fat that you were giving made the big difference. And the implication was that a calorie is a calorie when it comes to body fat loss. But the precision of those measurements was back from the 19th century. And it also didn't necessarily follow that it couldn't be that there was some precise combination of carbohydrates and fats that could cause calorie expenditure to vary. And if that happened, then you could still not violate any laws of physics, but you could have it. So that. And this is what Atkins claimed, right? He claimed that if you cut carbs enough in the diet, you would have a metabolic advantage, he called it, which was essentially saying that the body was inefficient at running on fat and would have to burn more calories as a result. And so you could have a situation where the number of calories that you were eating could be maybe even the same, or go up. He called it the high calorie way to stay thin forever, based on anecdotal reports from his patients. Look, I'm not eating any carbs, but I'm eating way more calories than I used to, and I'm still losing all this weight in body fat. Well, the only way to make that make sense is to have calorie expenditure go up. So, again, we think of calories in, calories out as these immutable things that we have total control over, and they're interacting with each other, and they may depend on the macronutrient distributions and things like that. And those are all perfectly legitimate questions to test. And so those were the kinds of studies that we were doing for quite some time, which was bringing people in to a metabolic ward where they lived with us 24 hours a day, seven days a week. And we would manipulate very precisely how much carbs people were eating, how much fat that they were eating, and measuring with the most precise methods that we had, how many calories were being burned, how much fat oxidation was there, how much carbohydrate oxidation was there, how much was body fat changing. Trying to see if what Rubner had suggested back in the 19th century was true in dogs was also true in human. And we devised the experiment based on some of the mathematical modeling that I had been developing when I first started my career at the nih. And the first study that we did was actually designed in a kind of an interesting way because we thought that we could show that Rubner, while maybe close to being right, it doesn't have to be perfect, right. That there could be a situation where you could see a discrepancy. And so we designed this study to test that, that. And in fact, we did see a discrepancy, clinically meaningless discrepancy, by the way. It's like, absolutely. It doesn't make a bit of difference when it comes to practical considerations for losing body fat, but we saw a discrepancy such that when the same people with obesity had a 30% restriction in calories coming only from fat, versus in another time, the same folks only from carbs, when they reduced the amount of calories coming in from body fat, they lost a tiny bit more body fat fat than they did when the same people had the same number of calories restricted from carbs, suggesting that a calorie wasn't exactly a calorie, but the difference was so minuscule that clinically it's totally meaningless. But as a background in theoretical physics, I think that even these kind of principle.

Rich Roll (37:31)

Yeah, if that is like a hard and fast principle, any deviation at all is worthy of investigation.

Kevin Hall (37:38)

Exactly. And so that's why I was excited by that result. Right. And, and kind of shocked when I saw like these competing diet tribes take that same study and say, oh, it's either completely flawed and worthless and it wasn't low carb enough or whatever. And then another group were pro low fat diets. Like, finally you've proved what we've suggested.

Rich Roll (37:57)

All of, well, this is. Yeah, I mean this is rampant in every tribe, in every diet cult.

Kevin Hall (38:03)

But the point is that the physiology is incredibly complicated and even how the body achieves this near equal to equivalence and even though it's not precisely equivalent is incredible. Right. Inside the body, it's like the hormonal system stands on its head in order to manipulate what the different fuels are shuttling between the different organs, how hormones are changing just to make it so that it's approximately true that when it comes to body fat changing, something that Rubner had no idea about, it was a black box for his dog experiments. He didn't know about insulin. He didn't know what the liver was doing, what the muscles were doing, what the pancreas was doing. No clue about the inner workings of the physiology. But it's just so fascinating that the implications of this is that we can survive as humans or dogs on a wide variety of macronutrient distributions. And when it comes to storing or mobilizing calories from our body fat, the professional organ that is there to store calories, it's more or less equivalent. And it doesn't have to be perfect.

Rich Roll (39:06)

The human animal is highly adaptive and resourceful. You know, what I take from what you just shared is essentially everything is more complicated than you think it is. Yes. Calorie in, calorie out, sure. But more nuanced than that, the carbohydrate insulin model or the hormonal kind of view of this whole thing. True, but also more complicated than perhaps we imagine. And then I think on top of that, there's the added layer of complexity, which is that the scientific method, by its very nature, is reductionist. And to apply a nutritionally reductionist approach to all of this is flawed in and of itself because just macronutrient ratios aren't telling the whole story. You have to contextualize it in the holistic food, like the food matrix itself. How much fiber is in this, and what does fiber do to the uptake of. Of calories, et cetera. And this is. It just gets super murky from there. And then perhaps I'm interested in, can you draw conclusions from all of this, given the vast complexity of all of it?

Kevin Hall (40:11)

I mean, it's incredibly hard. Right. And I think that as scientists, we have to be really humble in kind of saying what we think we know about a system and what things do we have a certain amount of confidence in and what things are just really beginning to be understood? And I think I want to take you back to it's not just the nutritional complexity of food, but it's the food environment that we find ourselves in. Right. So kind of going back to the comment about these different feedback loops that we talked about that are preventing us from losing more weight than we would like and the effort that's involved in keeping weight off in a given environment. Well, the funny thing is that, and we're only beginning to understand this, you take that same person and you shift them to a different food environment. What was effortful before is no longer effortful. In other words, whatever points that we're regulating our body weight and our appetite and our energy expenditure, those controls that are helping us regulate body weight, turns out to be incredibly influenced by the food environment that we find ourselves in. So I was doing these studies where we were manipulating macronutrients and observing these little tiny, clinically meaningless differences. But as soon as we started to do experiments where we basically said, look, eat however much you'd like, we're just going to change the foods that you're exposed to now. We are starting to see hundreds of calories a day differences. And when these people are being told, eat as much as you'd like, don't be trying to change your weight. We're measuring lots of stuff. What you don't know is we're measuring all your leftovers and we're going to calculate how many calories you decided to eat in these different food environments. And they're really short term studies, lots of limitations, very artificial food environment environments. But the point is that the environment is somehow interacting with our fundamental biology in ways that we still don't fully understand and is making it so that whatever point we're regulating or whatever narrow range of body weights that we're regulating is so influenced by the food environment and the neuroscience of that is only beginning to get unpacked. It's a really fascinating sort of observation that despite people not trying to change the numbers of calories that they're eating and trying to change their body weight, they're spontaneously changing them by hundreds of calories per day, spontaneously gaining weight, gaining body fat, losing weight, losing body fat without any effort whatsoever. And I think that's incredibly fascinating. And it also suggests that maybe that's what we're seeing in society writ large when it comes to the increasing amounts of average body weight and the increasing prevalence of obesity that we're seeing is that something about our food environment has changed. And the science of that is, I think, still beginning to get unraveled.

Rich Roll (42:59)

It's the environment, stupid. You know what I mean? It's like we can argue about the food pyramid or the food plate and like all this sort of stuff, but fundamentally it is, you know, you're going to eat what is in your environment. And if there is a core kind of theme or thesis to all of your work, it's that this obesity epidemic, this incredibly precipitous rise in chronic lifestyle ailments are primarily the result of toxic food systems. It's a systemic issue. And all of this focus on willpower or the failure of willpower and individual food choices has to be contextualized within that in order to really understand what's going on and craft solutions that are going to be effective.

Kevin Hall (43:43)

Right? Yeah, I think that that's right. And the degree to which some individuals might have a lot of success even within a given food environment, some of it is by limiting the foods that they're exposed to or limiting the foods that are on their list of things that they are even deeming possibly acceptable. So I sort of view that as a pseudo sort of local environment shift in that way. And the folks who have the privilege and the interest and the energy and the motivation to kind of engage in that sort of local environment shift and have access to the kinds of foods that are likely to drive the body weight regulatory system in the positive direction. Yeah, clearly they're going to have the most success. And there's lots of roles and lots of good reasons to kind of engage with those folks on an individual by individual level. And there's lots of people whose careers are made on that sort of thing. And I completely encourage that. But I think it overlooks the fact that body size in a given environment is 40 to 70% heritable and that some of us are more genetically susceptible to shifts in our food environment than others. And at the population level, what we have to account for is the full complexity of that food environment. So it's not just the foods themselves, it's the context and how they're advertised. What are the most inexpensive, the most convenient, the most readily available food foods? What are our skill sets? How are we relating in our social situations? Do we have supportive folks who are going to support us to make changes in our local environment, or are they going to resist those changes? It gets incredibly complicated, but at the broadest possible level, it just seems like the most obvious explanation for what we've seen happening. The shifts in the body size distribution, I mean, they started happening centuries ago in positive ways. Right. We saw increasing weight and increasing height wear as a result of nutritional deficiencies. Right. Something shifted as we kind of got into the middle of the 20th century. And that's where we get into the major shifts in the industrialized food system and whatnot.

Rich Roll (45:57)

So I love the fact that you're very kind of Anti diet tribalism. Like, listen, you can be healthy and sustain weight loss on a low carb diet, on a high carb diet. We can quibble around the edges there and people can fight and go to loggerheads over all that kind of stuff. But fundamentally, the 800 pound gorilla in the room is ultra processed food. So when we're talking about food environments, I mean that is the kind of lurking giant that's driving all of these deleterious health outcomes.

Kevin Hall (46:26)

Yeah, I mean, the way I sort of see it is even taking one step back, which is ultra processed foods are the consequence of what we call in the book the calories. So ever since the introduction of agriculture, humans have struggled to provide enough calories to feed populations. That has been the kind of devil's bargain that was struck when we moved into agricultural systems. As society populations could grow less and less people were responsible for producing food. And we got civilizations and whatnot. But at the same time, we were always threatened with, with population growth exceeding the ability of agriculture to feed populations. And there are obviously periods of mass starvation. Thomas Malthus, kind of a very famous 18th century thinker, basically made this observation that we're basically doomed to starvation because agricultural productivity and yield cannot possibly keep pace with what he saw as exponential growing population populations. We bucked that trend for the most part.

Rich Roll (47:33)

Yeah, I think we have pretty much. But it's interesting, it's crafty, it's amazing, it's kind of ingenious the solutions that humans came up with to solve this.

Kevin Hall (47:42)

It is amazing. And we think that, okay, yeah, that's 18th century Thomas Malthus. It was biologist Paul Ehrlich, even in the 1980s, was still saying that we would have mass starvation in America. Right around the same time we were seeing an explosion of obesity problems, prevalence. And it's amazing what we've been able to do with agricultural yields and industrialization of farming and whatnot. But we basically put in place in the middle part of the 20th century all of the resources and research to maximize calorie production, especially in places like the US and Canada and Europe. We did a calculation for the book, which I thought was kind of interesting. If you just take the four commodity crops for food, rice, corn, wheat and soy, and you ask the question, how many calories per person per day are produced in those few commodity crops? Turns out to be 15,000 calories per person per day. So six fold what the nutritional needs are. And we've been finding ways to kind of get rid of that glut of calories. Right. A Huge chunk of the soy and the corn goes to biofuel production. Right. Which for many. And animal agriculture, and then animal agriculture is the other big chunk of it. Right. And the reason why that sort of works to get rid of it is because, well, animals have a metabolism, right. They just, they don't just kind of translate one calorie of corn into one calorie of meat. Right. They waste a lot of those calories by living, essentially. And so. And so it's a very inefficient process, animal agriculture. And so. Yeah, so. So at the end of the day, you end up with something more like 4,000 calories per person per day in the actual food supply of America. And even that increase since the 1970s is more than enough to explain obesity. It turns out that about two thirds of the increase in calories in the food supply, after accounting for animal agriculture and the exports and the biofuel production, 2/3 of that increase went in the traps. Yeah.

Rich Roll (49:52)

You have this interesting correlation between the increase in food waste and the increase in obesity.

Kevin Hall (49:58)

Yeah. And I don't think it's an accident. I mean, I think that the point is that we have produced this calorie glut and come up with very clever ways of offloading it, both in terms of animal agriculture and biofuel production. And the other part is ultra processed foods. Right. It's taking those cheap, high yield inputs to the food system and coming up with incredible ways to transform them. Who would have thought you could take corn and make basically sugar, high fructose corn syrup for use in products.

Rich Roll (50:30)

Right. Subsidizing it to artificially deflate the price of it, to make it widely affordable, hyper palatable, highly caloric, nutritionally deficient. And also something about it that makes us want to eat it quickly so that we're ahead of our sort of appetite suppressant impulse.

Kevin Hall (50:51)

Right. And I think that there's a lot of people say that the food industry knows all the mechanisms by which these things cause us to overeat. I don't necessarily think that's true. I mean, I'm sure that they're trying to come up with incredibly tasty products that do well in the marketplace. Right. And when they fail, and many of them do fail fail, they basically re engineer a replacement and put it back. It's like evolution. It's like selection of the fittest products on the marketplace that are maximizing sales.

Rich Roll (51:20)

What happens if you put Fritos in a Taco Bell burrito? Do people like that? Exactly.

Kevin Hall (51:25)

It's like, let's try it out. We got a little focus group, they said they liked it enough to let's try it out. And yeah, that's the food environment that we're experiencing right now. And, and I think the point is both in the agricultural sector, all along the path we have these externalities that are not part of the equation. Right. All of the environmental damage that was done to kind of do this industrial agriculture, all of the problems with the animal agriculture, just from a moral perspective, as well as the manure that's produced and the methane that's produced and climate change and the depletion of the soil.

Rich Roll (52:04)

So the nutrients, the nutrients that end up in the food are less than they once were.

Kevin Hall (52:10)

Yeah, I mean there's some debate, there's some debate about that, I think about how important that is, but I think that there's certainly cases where that's been shown. The other big externality has been health care costs. Right. I mean the fact that we are experiencing this dramatic increase in diet related chronic disease that is essentially bankrupting Medicare, Medicaid and the health system sector. And to think that this entire process of solving Malthus, which is essentially we've solved Malthus problem, right? And we have to do something to kind of change this, not just for the health crisis, but the fact that we're going to have 10 billion people on the planet in not too far distant future, that solves Malthus problem because the population is no longer expected to increase. What do we have to do to the food system to both ensure that we have equitable distribution of calories and that those calories are actually healthy for us and the planet? That's the grand challenge of agriculture and nutrition and food science for the next several decades. And we need to think about it in this context. In some sense, the obesity and diet related chronic diseases are the epiphenomenon. They're the thing that happened because, because we front loaded all those calories in the agricultural system and now we've got to figure out a way to kind of steer past that. Fortunately, we have some therapies that are entering the market that can help the folks who are most genetically susceptible to those changes in the food environment. But we've got to think past that as well and look to see where do we want to end up when we have to feed 10 billion people a healthy diet that's equitably distributed as well as sustainable for the planet.

Rich Roll (53:59)

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Kevin Hall (58:32)

Yeah, sure. I mean, let's go back even before the last election, right. So before the last presidential election, this was a bipartisan issue. Right. And we can go way back when it wasn't a bipartisan issue with Michelle Obama and the let's Move campaign. It was clearly a Democratic issue and people were interested in proving our food and in addressing obesity. That was clearly a. Yeah, that didn't go so well. Did not go well. Right. For all its good intentions and whatnot, it did not go well. But there was something different that was going on. I think a lot of it had to do with the discussion about ultraprop because we've had these discussions back. It's either been sugar or saturated fat or sodium and salt that have all been public health enemies and they've all had. There's a lot of data behind those kinds of campaigns and why it would be better for people to eat less salt and eat Less saturated fat and eat less sugar and things like that. And I don't think there's many folks who disagree with it, but they didn't really capture enough public attention, especially at the political level, that I don't remember seeing a Senate hearing about added sugar. Right.

Rich Roll (59:46)

Well, it was interpreted at that time, and perhaps that was a failure of the messaging as an affront to personal liberty. Like, the government's gonna tell you what you should eat. And how dare they kind of intrude upon my personal choice. As opposed to, hey, there are shadowy giant corporations who don't have your best interest at heart here and they're out to get you. Or, you know, there could have been a different way of communicating that message at that time.

Kevin Hall (60:13)

And I think possibly that's part of what this idea of ultra processed food has kind of brought to the table, has been the fact that all of these things are important about the nutrient properties of the foods that there are and the way that they're marketed and the overall system of food that we're experiencing and how it's changed since the middle of the 20th century. Century. And so, yeah, we had like Bernie Sanders, Cory Booker. You couldn't tell their comments about this from Bill Cassidy or RFK Jr. At the time. It was like. It was. And I still think that if you talked to Cory Booker today, he would probably tell you, well, he's on honeymoon, I guess, right now.

Rich Roll (60:51)

Yeah, he's on honeymoon right now. But no, but this is an issue that he cares deeply about.

Kevin Hall (60:56)

Exactly.

Rich Roll (60:56)

And has been working on for a very long time.

Kevin Hall (60:58)

Exactly. And so I still think that for this particular set of topics, there is bipartisan support. And before this current administration, nutrition science has been funded horribly by the NIH for a very long time.

Rich Roll (61:12)

So it's not a new situation that the funding has been anemic.

Kevin Hall (61:16)

Exactly. And we've been focused. I think this is a good justification for doing this. But there's been a huge focus on the sort of biomedical program of let's figure out how to treat and cure disease. Right. No one's going to argue with that. Right. Everyone wants to be able to cure cancer and treat diabetes with better therapies and whatnot. But there has been less emphasis and less funding on nutrition science and prevention and the environmental drivers of disease prevalence.

Rich Roll (61:46)

Because it's a great question, is it big food lobby money that is influencing appropriation?

Kevin Hall (61:56)

I don't know. I honestly don't know.

Rich Roll (61:58)

Lack of political will.

Kevin Hall (61:59)

I mean, I would say that there's probably. Let's Face it, when do people get exercised about disease? It's when they get a disease or a loved one gets a disease. Right. And the first thing they want is a cure. So there's huge amounts of lobbying from organizations and people who have already suffered the consequences of, of diseases that were put in motion by environmental drivers a long time ago. And the ask is not, let's fix those other things that have driven this for my grandchildren. The ask is I want to know what it is that I'm going to have to do to get a cure in the few years left that my parent or my child has this disease. That's a very powerful message that resonates with people. And I think I don't, I don't want to take anything away from that.

Rich Roll (62:51)

Sure, the acute nature of it, but far more people are walking around thinking how come I'm getting fat and how come I can't lose weight? Like, I mean, that is just, you know, that's like you're capturing like 80% of the population or probably more.

Kevin Hall (63:05)

And to be fair, we've come up with pretty decent treatments in recent years for several of those things. And I think that that's a good thing for those things.

Rich Roll (63:13)

But it doesn't mean you're not root covering cause solutions.

Kevin Hall (63:16)

They are not root cause solutions. That's correct. They are solutions for some people and I don't think we should minimize that. And like I said, they are part of the bridge that's going to get us to where we need to go with our food system.

Rich Roll (63:28)

By this you mean like bariatric surgery or GLP1s?

Kevin Hall (63:31)

Yeah, exactly. Like these are treatments for the ones, the folks who were most genetically susceptible to the environmental changes that have put in place the increase in obesity prevalence and the down consequences of that. We thankfully now have effective treatments and some of them can scale at a level that will help many of those people. I think that's a great thing. But I think you're right to point out that funding to figure out how are we going to move past this and what was the cause of these problems in the first place. It's been underfunded and nutrition science in particular has been underfunded. And I think it's tragic. And I experienced that even in the last administration after we had this big paper on ultra processed foods come out showing that when people are exposed to environments with lots of ultra processed foods, they ate many, many more calories, they spontaneously gained weight and gained body fat, shocking the result and then shifting them to a minimally processed environment. Again, these environments were matched for the number of calories that were presented to people. The macronutrients, the glycemic load and the fiber and the sodium, and yet.

Rich Roll (64:42)

And the nutritional dark matter, which we.

Kevin Hall (64:44)

Haven'T even talked about. So they've experienced this change in their food environment spontaneously. Just. I just decided to eat less. I'm not trying to do anything. Just effortless shifts. After that study came out, and it garnered way more attention than I thought it was gonna get, they wanted to close down the unit at the NIH.

Rich Roll (65:06)

And this was. This was prior to 2020. This was before the Trump administration.

Kevin Hall (65:11)

This is 2019. So the same year that that paper came out, we were told by the CEO of the clinical center that they were going to close down the metabolic unit. I remember sitting in a room, and afterwards I said, I don't see how I can have any confidence that I can continue to do our studies if this unit's closed. And he said, yeah, you shouldn't have any confidence that you can continue your studies.

Rich Roll (65:36)

And what is your theory? I mean, what is the motivating.

Kevin Hall (65:42)

The motivating fact was that I think he had plans for that facility that he thought were better suited, and we can have a debate about that. And he was in a higher position at the NIH than I was. And, yeah, I think that there are several theories. I think he wanted to maybe set up an Alzheimer's unit. I'm not exactly sure what the different competing theories were, but we could have a debate about that. But the debate was sort of shut down. I ended up finding out someone at a higher level at HHS who had read our paper. And I said, hey, I heard you read our paper and were intrigued by it. It's too bad we won't be able to figure out what the mechanisms were, because the unit's going to get close.

Rich Roll (66:20)

It's outrageous to me, because our entire epidemic of chronic lifestyle illness all tracked back to this. And not only is this driving all of these incredibly poor health outcomes and debilitating millions of people unnecessarily, necessarily, it's at the root of what's ailing our healthcare system. And so, from an economic perspective, which then becomes a national security issue, these are gigantic problems that need to get solved that are important for the sanctity of our democratic union. Fundamentally, it's more than just people are getting sick. This is why healthcare is so expensive and so bureaucratic and so kind of overwrought right now. And we have to solve it. If we want to figure out health care.

Kevin Hall (67:12)

I completely agree. And so while we were successful at pushing back against that attempt at closing our unit. So that's why in the run up to this last election, with the attention that this was receiving on both sides of the aisle, I was super excited. Right.

Rich Roll (67:26)

I thought, here comes a guy and he's talking about this stuff that I'm studying and that I care about.

Kevin Hall (67:33)

And it has.

Rich Roll (67:34)

But prior to that, before we even get there on the timeline. I know. Is it true that you almost got fired for writing this book? Like this is before the current administration?

Kevin Hall (67:43)

Right, that is true also.

Rich Roll (67:45)

What? Yeah, like you're just a guy at NIH doing research on processed foods and metabolism.

Kevin Hall (67:52)

Yeah, that's true.

Rich Roll (67:53)

What's the big threat?

Kevin Hall (67:54)

Well, I think there's a couple things, right. And it was expressed to me that two main concerns. One was that we have an entire chapter about policy. The NIH has always sort of prided itself as we provide the science. We don't opine about policy decisions. Right. We don't want to get involved in policy decisions. And the second thing that they pointed out was that the other thing we point out is in the book, there's a lot of. I wouldn't say it's debunking, but it's a lot of challenging of claims that various folks are making in different spaces, like the different diet communities, the different folks who are selling supplements, who are selling precision nutrition programs. And they didn't want pushback from these folks.

Rich Roll (68:43)

And because you're a government employee.

Kevin Hall (68:45)

Exactly.

Rich Roll (68:46)

It's creating a headache for them.

Kevin Hall (68:47)

Yeah. So I initially said, look, what if I just kind of not put my affiliation on there? And they didn't agree to that. And they said, no, if you're an author of the book, you're going to be disciplined and likely removed from your position. Position. And so I actually had to hire a lawyer who is well known for. He's well known for basically representing clients who write books after they leave the national security space. And he's like, are you trying to reveal some classified infrastructure? I'm like, no. And he's like, I don't understand it. This is the most bizarre thing he'd ever seen. Anyway, he was able to kind of basically get the NIH to assent to letting me be a co author of this book. And by the way, keep your job. Keep my job. Right.

Rich Roll (69:34)

Which.

Kevin Hall (69:34)

Which I've since left. Which is the other part of the story. Right. So, yeah. So I guess the point was, is that after that was Resolved. And I thought I would be continuing with the NIH and this new administration was coming in and that there was bipartisan support for finally kind of investing in understanding what's going on and tackling these issues of diet related chronic disease and ultra processed foods. I was very excited about this. And in fact I started working with the director of the NIH Office for Nutrition Research about We've been doing our studies which are pretty small scale, they take years to complete because we can only house two or three people at a time. What if we had facilities for other researchers where we could house people more comfortably, not in a hospital and keep dozens of people at a time, get answers to these questions that the American people deserve in a matter of months rather than years. And we could cycle through, through different hypotheses and different mechanisms that we were studying. And we started to work on a plan of how we would do this. And I was trying to contact members of the MAHA kind of leadership to talk about this, but they were too busy talking to social media influencers at the time. But we were plugging along, doing our work. Eventually I wanted to be able to kind of present this sort of plan to folks. And in that transition period after the new administration took over, we started to see that certain topics were deemed sufficiently politically interesting that any sort of work that would be communicating results, going to conferences, any new programs had to go up to the level of the Department of Health and Human Services and be approved by a political appointee. And so I started to experience this directly. The first occasion was I was supposed to give a talk at the Bloomberg Philanthropy's annual meeting about some of our work on ultra processed foods. And for the first time at that time, 21 years at the NIH, I was denied the opportunity to give a talk at the conference. Now it was unclear exactly at the time time was this because of travel restrictions. And so I went back to the Bloomberg folks and said, could I do this remotely? Would you mind if they're like, yeah, no problem. So re requested. The ability to do this still denied. This was at a time when my colleagues were being allowed to give talks, especially remote talks. So there was something special about the results that we were trying to present that was being being suppressed in this way. We were interested in the question, does ingestion of ultra processed foods hijack the brain's reward system in the same way that cocaine does? I guess the question is addiction doesn't necessarily have to occur through this particular biological pathway. Okay, yes. This has been a common phenomena in that drugs like cocaine and methamphetamine, even nicotine, cause an outsized surge in dopamine in the brain, which leads to a bunch of adaptations that can lead to addiction. There's a very long history, even in the obesity space, of looking at neuroimaging studies of the brains and dopamine receptors in people with obesity and people who are lean and saying, hey, look, the brains of people with obesity look more like people who've been addicted to cocaine than the folks who are lean. And so there is this particular neurobiological mechanism of addiction, which is well understood with cocaine. Cocaine. But it's always been hypothetical when it comes to food addiction. And so that's the reason you do research in this study. Right.

Rich Roll (73:26)

So let's look at it and figure out if that's truly the case.

Kevin Hall (73:29)

Exactly. And so what we found in this study was a very large study, the largest study of its kind. And it was designed to assess the question of whether or not people with obesity have the same sort of adaptations in dopamine receptors that you see see in people who are addicted to drugs over the long term, implying that people with obesity might be more likely to have food addiction. And secondly, whether or not they see this outsized dopamine response similar to cocaine ingestion, and is that different between lean and obese people? And we did not see that latter effect. And so we wrote this paper. And the paper was written and submitted before the administration came in. It was accepted for publication. We were starting. Starting to want to talk about it at conferences. And so you're right that it was perceived, I believe, by folks at the political level at HHS as saying, I don't need to think about it. I know that they called a reporter from the New York Times, the communications director, and said, the results of this paper don't match RFK Jr. S thoughts about ultra processed foods.

Rich Roll (74:40)

It was politically inconsistent, convenient. And so they interfered with your ability to have a press release and to speak to the New York Times about this.

Kevin Hall (74:48)

Correct. And they edited my answers to the.

Rich Roll (74:51)

Reporter'S questions, written responses, where they editorialized what you had to say without giving you the opportunity to.

Kevin Hall (74:57)

Well, no, actually saying that I wrote it.

Rich Roll (75:00)

Oh, really?

Kevin Hall (75:01)

Yes, it was a tribute to be.

Rich Roll (75:03)

It was provided to them in your words, Were you able to get a correction from the New York Times out of that?

Kevin Hall (75:08)

No, I was in communication with the reporter for the New York Times, so I just made sure that she quoted only from the sections that I had written, not the embellished sections. That downplayed the study. So yeah, this was like direct interference with the ability to communicate these results. And so at the time they're trying to get as many people to leave the NIH as possible and they put up this early retirement option several weeks later. Later. And so after experiencing this was like.

Rich Roll (75:36)

In the middle of doge.

Kevin Hall (75:37)

Yeah, yeah, exactly. And we had ongoing studies and again, I wanted to kind of talk about the plans for how could we improve this situation. Completely aligned with the goal to make America healthy again, that ultra processed foods, we need to better understand how they might work and what the mechanisms are. And so I wrote to RFK Jr. His senior staff, I wrote to the NIH director and said, look, here's what I've experienced. At that time, we actually also weren't able to buy food for our research participants. We couldn't buy research supplies. We weren't able to rehire people who were leaving on a regular basis that run our studies. It was like a very bleak time. Fortunately, some of those things have turned around a little bit at the the nih. They're still experiencing some of these difficulties purchasing research supplies, for example, still to this day. But we were experiencing really acute problems. And I'd been talking with our scientific leadership, like, what's going to happen here? Right around that time it had leaked that there's going to be a 40% cut to the NIH budget and very dire time. So I wrote to these folks and said, look, not only are we experiencing these problems, problems, but we're totally aligned and we can make a lot of progress. In fact, I told them about this ongoing studies, how we're making progress, understanding mechanisms of ultra processed foods. Why do they make people overeat? That we'd been able to redesign an ultra processed diet that was still 80% of calories from ultra processed foods that didn't actually cause people to overeat by focusing on mechanisms that we could do a lot more in the future future if we kind of engaged in this plan. And I sent them the copy of the plan, actually requested a meeting and I basically said, otherwise, I can't see how we can continue research in this space. And I'm going to prepare to retire through this program. And so I didn't hear anything as a result of that, except a colleague of mine said, hey, are you really going to retire? And I'm like, possibly. How do you know? And he said, well, well, your email was circulated among senior staff at nih. And so someone read it, but nobody reached back out to me. So I spent the next weeks kind of reassigning staff and reassigning my clinical protocols and closing down a 20 year career at the NIH because I didn't see a way to kind of move forward if we're going to be interfered with in this process. And that there was no interest in engaging in this type of topic at the same time that they're holding meetings with folks drinking raw milk in the White House.

Rich Roll (78:24)

I mean, it's just unfortunate because there is a lot of energy around ultra processed foods and what's happening there. And he's very much a flashpoint and drawing attention to this. And that's a good thing writ large. And you could have been this ally. You're the guy who's looking at this more closely than anybody else. It's confusing why there couldn't be some kind of consensus about how to move forward together on this. Yeah.

Kevin Hall (78:53)

And even more disappointing. And I think one of the things that solidified why I think I made the right decision, because obviously I agree with you and I think that we could have made a lot of progress after I left. And it made a little bit of press coverage. Sure.

Rich Roll (79:10)

Yeah. There was actually a lot. Yeah, there was quite a few where you were. That must have been strange for you. It was a little strange. A scientist at nih, suddenly Jake Tapper is talking about you and you're just kind of everywhere.

Kevin Hall (79:21)

Well, the interesting thing about. So the day that I talked with Jake Tapper earlier that morning, I met with the NIH director, the new NIH director, Jay Bhattacharya. Jay Bhattacharya, Yeah. So he saw the New York Times article that came out, I think the day or two before that. And he said he wanted to meet with me. And so I went back to the NIH and he wanted to know what happened. And I was there. Him and the deputy director for intramural research. Intramural research is the part of the NIH that does their own studies. Extramural is the granting part of the nih. So this was basically my boss's boss's boss and the NIH director. And he was interested in the censorship thing because he feels like he was censored during COVID And it was clear he could probably have talked the entire meeting about that. But I tried to transition and he told me he had not seen my email. And I believed him. I mean, he was new to the job. Job. Somebody probably saw it in his staff. But I believed him when he said he hadn't seen my Email. And what I wanted to focus attention on was, what about this plan? The purpose of my email was, yeah, I wanted to tell you about the troubles that we were experiencing and the censorship and whatnot. But the main part was, could we get on the same page and actually improve the science, investigate this to get the answers that the American people deserve? And you're right. There is so much passion about this issue right now. And it had been clear that he saw the email that I wrote, and he saw the plan, and he said, yeah, I'd really like to work with you on this. And he shook my hand and he said, welcome back. And I said, well, I'm not back yet. I've got nothing to go back to. My lab has been been closed. My staff has been reassigned. My protocols are being run by other investigators, but I'd be really interested in working on this with you. And he said, okay, we'll talk to Nina and we'll figure something out. And I got back in touch with the director of the Office of Human Nutrition Research, and we continued to work on this program. He presented it again at the nih. We were talking about. About funding for a facility maybe even located at the USDA Beltsville facility, which was slated to be closed. They have a big metabolic kitchen and buildings that could be renovated. And I thought I was going back. I was pretty sure the director of.

Rich Roll (81:48)

The NIH basically said, welcome back. I mean, if he can't hire you back. Yeah, it's like, if he can't hire you back, I mean, who's going to?

Kevin Hall (81:56)

Exactly. So for weeks, I was working with Drew at the Office of Nutrition Research and the intramural, the deputy director for intramural Research and kind of putting together this plan of what we would do. And then out of the clear blue sky, Drew calls me up one day, and he said, I don't know what happened, but it's killed. We're not doing this. He had no explanation. He said, I tried to get an explanation, but I couldn't get one. He said, the closest thing that I can think about is that this is personal. It has to do with you. And I'm like, like, well, that doesn't make any sense. Because if they wanted to make it personal, they would do it and then not hire me back. Right. That would be the biggest way to get back at me. I don't understand what happened. But apparently somebody decided, for whatever reason, and still has not been made clear, that actually investing in this research to better understand how our diets and our food environments Affect diet related chronic disease was not sufficient of interest to actually fund that research. What I've sort of interpreted this as, and since we've sort of seen other examples of this, is that science only complicates rhetoric. It only introduces complexity and nuance. And when you're trying to make a case for something, especially if you're kind of come at it and you're a lawyer, you know this, you want to come at it with the strongest possible case and rhetoric that you can come at it with, and you want to downplay evidence that might introduce that nuance and suggest it maybe isn't so reliable and upplay evidence that is really supporting your side and doing really good science can only potentially complicate your narrative. And a complicated narrative is more difficult to get action on than a simple narrative. And my view has been that unfortunately this administration views science as a complicating factor getting in the way of what they want to achieve as opposed to.

Rich Roll (84:11)

I mean, the most charitable interpretation. That's a very charitable interpretation. The most charitable would be, listen, we really want to solve this problem, but we have to have these reductive talking points and we can't have anything compromising that because. Because that will distract from the solution. The less charitable interpretation is that you're a political liability because objectivity is in opposition to the political aims. And when it comes to your solutions, your systemic solutions, they're at cross purposes with the deregulation mandate of the administration outside of hhs.

Kevin Hall (84:49)

Yeah. And that's a huge challenge for them. Right. Is that there is is a presidential executive order that for every new regulation you have to remove 10 others. Right. So how are you going to introduce new regulations on food if you have to remove 10 other ones at the same time? And I think that that's part of the other thing, and I know Jessica Nurik talked at length about this, is that the rhetoric doesn't match the actions. Right, Right.

Rich Roll (85:13)

You guys agree on the fact that Maha is identifying the problem correctly. It's just that there's a difference of opinion when it comes to solutions.

Kevin Hall (85:23)

Right. And that I'm a firm believer that science is the best thing that humans have come up with to get closer to the truth. And science based kind of policies are the best thing that we can have to actually improve the situation. And so we need to invest in the science in order to improve the situation. And if you don't, if you just think that you have it all figured out and the history of nutrition and, and food science has been on Repeat, as we discuss in the book, people thinking they've got it figured out and they come up with a very simple sort of narrative, only to fall apart when it's subjected to critical tests. And yes, we're making progress, but very often those simple narratives fall apart when you subject them to tests. I think that the example that we were coming up with was the dopamine story doesn't seem to be holding up as well as we thought. It doesn't mean that people aren't addicted to food and ultra processed foods might be more addictive in other ways. But it definitely complicates the narrative if you can't say, yeah, it's exactly like cocaine.

Rich Roll (86:32)

Well, I appreciate your candor in sharing that story. I'm sorry that that happened to you. I'm sure you'll find your next thing and perhaps even reflect back and think, well, it's good that this happened because now I'm here. You're trying to figure that out, right? Right now. But I want to, I want to shift now to trying to provide people with some actionable guidance while also appreciating. Appreciating the complexity of all of this. I mean, this is going to publish in a couple weeks. Like prior to the New Year. Everybody's thinking about their New Year's resolutions. I'm sure there's a lot of people watching or listening who are thinking about how they're going to try to finally lose that extra 10 pounds or whatever it is, is. But they're also on the precipice of all kinds of social gatherings where there's going to be lots, their food environment is going to be less than ideal. And what is your counsel to the average person who's trying to navigate their food environment, make better choices, and have a better understanding of what's really going to drive sustained weight loss and better health outcomes over the long haul.

Kevin Hall (87:42)

Yeah, yeah. So. So I think a couple of points. One is one that I think people, again, too often tie to weight loss, but the effects are especially acutely. But the effects are, the positive effects are completely independent and that's exercise. Too often people around the new year and they kind of come up with some New Year's resolution to join a gym or start an exercise program or hire a personal trainer, and they tie their success to what's happening on the, the scale. That's, I think, completely misleading. Right. Because even if you don't lose a pound or even gain a pound, if you become regular in your exercise habits, both your function, your day to Day function, your ability to kind of get around and move about in the world, as well as many metabolic consequences are independent of how much weight you lose. And so I think that's one factor, is that people should not tie their success at exercise with what happens on the scale. And I think that too often we do this, especially in that New Year's time.

Rich Roll (88:44)

One of the things you talk about in the book and in your work is there is that not all fat is equal. There is a distinction between problematic fat and I guess, what you would call healthier fat. So just the number on the scale or how much adipose tissue you have doesn't really tell the whole story. Worry about your health or lack thereof.

Kevin Hall (89:05)

That's right. Yeah, exactly right. And it's the function of your fat as well as where you're storing excess calories. And if you're storing it outside of your fat tissue, your adipose tissue, if it's in your muscle, for example, or in your liver, then that's the problematic areas. And exercise is potentially beneficial for both of those things, even if the overall adipose tissue doesn't change or change its visceral fat. So, yeah, visceral fat is a little bit. It's one of those popular bad guys that people talk about, but I don't think there's really good evidence that visceral fat per se, is bad. So visceral fat, again, is adipose tissue. It's a small amount that's around your organs. It's not actually in your organs. And there's some evidence to suggest that it's really not contributing as much as we originally believed to poor metabolic health.

Rich Roll (89:52)

Yeah, because I've always thought, oh, well, that's the bad one.

Kevin Hall (89:55)

I mean, it's.

Rich Roll (89:55)

And it's the one you're not. You don't even know if you have it necessarily.

Kevin Hall (89:59)

Yeah, I mean, and it tracks a little bit more closely with liver fat than subcutaneous fat. It's still a little bit debated about how relevant visceral fat is per se to metabolic health. So, for example, if you do bariatric surgery and at the same time you remove visceral fat, you can just take it out a huge chunk. And therefore you don't see the same sort of. People talk about it dumping into the portal vein of the liver and having inflammatory properties, you get rid of that. The meta analysis suggests you're no better off having your visceral fat removed from a metabolic standpoint than you are from just getting the bariatric surgery. And in fact, if you cut up subcutaneous fat, you don't get any of the metabolic benefits of losing weight. Right. So there's something special about weight loss per se, that doesn't have to do with the surgery, that doesn't have to do with the visceral fat or even subcutaneous fat per se. So it's more likely to be the fat that's in your muscle cells, in your liver cells, around your pancreas that are the more problematic areas. But the point is, exercise is beneficial metabolically, regardless of whether not you're losing weight, regardless of whether or not you're eating.

Rich Roll (91:16)

It's such a boring answer.

Kevin Hall (91:17)

It is a boring answer. Give me the.

Rich Roll (91:18)

Behind the velvet rope. You know, Kevin.

Kevin Hall (91:21)

Yeah.

Rich Roll (91:22)

It's like, oh, exercise. Yeah.

Kevin Hall (91:24)

Gee, never heard that before.

Rich Roll (91:25)

Right.

Kevin Hall (91:26)

But I think the new part, I don't know how new it is, but the new part is that people, they tie it so closely to weight loss about whether or not they're succeeding or.

Rich Roll (91:34)

It'S the reason for doing it.

Kevin Hall (91:36)

The reason for doing it. Right. I mean, the benefits for weight loss don't seem to show up acutely. They show show up later. Maintenance of weight loss is pretty closely tied to how physically active you are.

Rich Roll (91:47)

So it seems like you're saying, don't obsess on weight loss. Focus on eating healthier foods and exercising.

Kevin Hall (91:55)

And improving metabolic health. That's right. And you can do that? Yes. Fat loss can help with that. But whatever you're gonna do to change your lifestyle or change your. To actually lose weight, you've got to. Got to be willing to do that permanently. Because I think, again, that's one of the things that people have this idea that, well, I'm going to go on a diet to lose weight in the new year.

Rich Roll (92:19)

And then once you do that, everything's great.

Kevin Hall (92:21)

Yeah.

Rich Roll (92:21)

You can put your foot off the pedal. I mean, after studying the Biggest Loser contestants and all, I mean, you must have learned quite a few things about the difference between people who are able to sustain healthy habits. And, I mean, this gets into psychology, obviously, but. And those that lapse, right?

Kevin Hall (92:38)

Yeah. I mean, so, no, I didn't learn very much.

Rich Roll (92:42)

You didn't? Okay. Some people do and some people don't.

Kevin Hall (92:45)

I'm a little bit of a bonehead in that regard. I tend to look at things, you know, if it's not happening in the hypothalamus or the reward regions of the brain, like, that's too much cognition. That's a messy psychology from the soft sciences. Okay.

Rich Roll (92:59)

So, yeah, Some people, people might learn a lot.

Kevin Hall (93:02)

Not me. But yeah, I think it's really interesting though because I think that again, one of the chapters of the book, we talk a lot about precision approaches like you're the unique snowflake and there's huge variability in the amount of weight loss that people have. And if only we could identify what special biological properties you have that would promote weight loss on a given intervention. I don't think there's good evidence for that yet. And the presumption seems to be that there's some magic biological driver about who is a success story and who's not. But I think that again, getting to the softer sciences of this, whether or not you have a supportive partner or supportive family, whether or not you have the economic means to kind of make these changes and change your local environment in ways which I think you can, people do have some agency to kind of change those kinds of things. Those are going to be much more important than signing up for the latest CGM GUT microbiome analysis, which is in my view vastly overhyped at the current time and being oversold to people. There's some evidence of that that we present in the book, that these things are not as reliable as they're being made out to.

Rich Roll (94:18)

Yeah, I mean, I think they're tools like anything else. I think they lack adequate amount of education as a sort of central piece to it and the technology isn't quite there to provide, provide the best kind of actionable recourse as a result of these. And I think that the data points, there's so many data points now with all these wearables and it's disorienting and you don't know what's important and what's not. And so you're making health choices based upon short term data reports that don't necessarily mean anything and can potentially drive poor decisions around.

Kevin Hall (94:54)

That's right.

Rich Roll (94:54)

Especially with CGMs. Like you see these spikes and you think, oh, well, the solution is just not eating anything that's going to spike my insulin. So it's like, all right, well you can just eat fat all day long. It's probably not great, but you're going to have a nice line, right?

Kevin Hall (95:07)

Yeah, that's right. And I think that the problem that I have is that the foundational science.

Rich Roll (95:13)

Hasn'T been done right, so the measuring isn't there.

Kevin Hall (95:17)

So I mean, one of the studies we did, especially when we have this complete control over people's environments and in fact the order of the meals and the timing of the meals. We know all of this about the subjects that we had on. We would basically have two CGMs simultaneously, one on the abdomen, one on the arm, as according to the manufacturer's instructions. And yeah, the results that you get are correlated, but you have this huge variability where the same people simultaneously eating meals, one is rock solid and the other one is causing a spike.

Rich Roll (95:47)

If they were accurate within a certain reasonable range, would you have a different opinion on that? Because it does seem to me like anything that connects, connects you more deeply with the habits and the choices that you're making and can kind of show you evidentiary proof of like, what you're doing and what it's doing to you is probably a good thing.

Kevin Hall (96:06)

It can be a good thing if you know how many times you have to measure the thing to have a reliable response. And our data suggests that that's probably more like 10 times. Right. Like if you measure the same, similar responses to the same food or same meal 10 times times, then you probably have a pretty reliable response. And that's even in the highly controlled situation.

Rich Roll (96:27)

I mean, that's true of everything. I mean, just as an athlete, like wearing heart rate monitors, I know my chest monitor is always going to be more accurate than whatever's on my wrist. It doesn't matter the sensor. But even if all I have is a wrist sensor, I know that that number isn't exactly accurate. But if I do it over time, it's the variability in that number that still provides me with some value.

Kevin Hall (96:48)

And I think that knowing that and having done that sort of research in advance is what's lacking this particular space. And instead what you get is you get people who see something on just a couple of occasions, they see their blood sugar spike eating a banana and they do it on two or three occasions and they think, oh, that's my response to bananas is. And what if that person really loves bananas and it's not really a reliable response because they haven't done it in.

Rich Roll (97:14)

The past, they're going to eat bacon.

Kevin Hall (97:15)

Instead and they eat bacon instead and you've made their life measurably worse because they don't enjoy the bananas. And potentially from a healthy. Because they're now eating bacon instead of bananas.

Rich Roll (97:24)

But I think these things, I mean, listen, as human beings, we like little shiny bottles, of course we do. These things are fun. But you're like a Pillars guy and it's like, listen, just stay away from the ultra processed foods. Try to better control your food environment. When you go to the grocery Store, stick to the far aisles where it's real food and exercise and get out. All these other things are like, they, they're like cherry on top of the sundae sort of thing.

Kevin Hall (97:50)

They are. And they can be distracting, I guess is the point. And I think the other thing is when it comes to ultra processed foods is that it is an extremely broad category. Right. So the way it's defined academically, how.

Rich Roll (98:01)

Do you draw that distinction? Because I often think like, okay, so I wear a whoop tracker, right? So, and I love it and it's great. And you know, I look at the data points over a broad period of time. Like I don't get caught up in every single day or whatever. But it has a little diary function. It's like. And you can choose which little checks things. And it's like, did you eat too late at night or did you eat processed foods? And I'm like, well, I had some olive oil and I had some. Is that a processed food? Is that not a processed food? What's the difference between a processed food that you might consider healthy and an ultra processed food that is just off the table?

Kevin Hall (98:38)

And what I'm adding is that not all ultra processed foods might be off the table either because it is even within that category as defined academically. So there's this Nova classification system. Basically it groups foods into four different categories and it has nothing to do with their nutritional properties. Which is kind of a lot of the Kirk fuffle about ultra processed foods is it doesn't talk about saturated fat or sugar or sodium or anything like that, or even fiber. But you've basically got whole foods. You can wash them, chop them up, freeze, freeze them, all sorts of things. Your produce, your even canned produce would be considered a minimally processed food as long as it doesn't contain certain preservatives and that are kind of more technologically advanced. These are the minimally processed foods. So eggs, meat, poultry, fish produce, legumes, rice, those kinds of things. Then you've got processed culinary ingredients. These are the things that I like to think of as. You don't eat them on their own. Olive oil, right. No one's guzzling olive oil butter.

Rich Roll (99:41)

I think maybe Stephen Gundry is.

Kevin Hall (99:43)

Oh, that's maybe true.

Rich Roll (99:45)

Anyway, go ahead.

Kevin Hall (99:46)

I use the butter example too, but my youngest child actually did eat like half a stick of butter once.

Rich Roll (99:52)

Don't some of the carnivore people do that?

Kevin Hall (99:54)

Maybe they do.

Rich Roll (99:55)

Anyway.

Kevin Hall (99:55)

Anyway, these are the edge cases, my son and the carnivore people. And sugar would Be another example. Right, but the point is that you are using these so called processed culinary ingredients to mix with category one, minimally processed foods to create meals or preserve them, or enhance their sensory qualities. And in fact, that's the definition of Category 3, which is called processed foods. So breads, pastas, fermented products, these would all be called processed foods. And then basically everything else is what's called ultra processed food, processed foods. And so these are typically using a lot of these cheap agricultural inputs, things that you would not find, ingredients that would not be found in restaurants or home kitchens. They're often using processes and manufacturing methods that are not commonly used, things like extrusion technologies and all sorts of other kinds of things. Preservatives, Preservatives. Also some categories of preservatives affect, they belong to a very historical way of preserving. Fermenting is a preservation technique that belongs in the processed food category. But yeah, other kinds of preservatives, cosmetic additives, flavor additives, those would count as something as ultra processed. So within that category, all the kind of typical junk food type things, much of the fast food that we have, but also things like whole grain breads that you buy at a supermarket, things like many of the plant based meat replacements would be ultra processed foods, a lot of things like some flavored yogurts and things that many people think are probably beneficial for health. So it's an incredibly broad category of foods. And the question is, you know, it was an empirical question for a long time is, are diets high in ultra processed foods connected, linked with diet related chronic disease? I think that everybody realizes the answer to that is yes, they are linked mechanistically. How that works is still not fully understood. I think a lot of it is probably downstream of obesity. Right? Something about this category of foods causes people to overeat calories and gain weight and have excess body fat and as a result having many of the downstream complications which kind of overlap with many of the things that ultra processed foods have been linked to. Obesity, type 2 diabetes, cardiovascular vascular disease, several forms of cancer and all cause mortality.

Rich Roll (102:26)

In fact, at the same time, you would probably also say if your ultra processed food of choice is very high in sugar and then you have type 2 diabetes, maybe there's a connection.

Kevin Hall (102:36)

Yeah, yeah, yeah.

Rich Roll (102:37)

No, that extends beyond purely obesity or if you like salty stuff and you have high blood pressure.

Kevin Hall (102:43)

Yep, yep, that's true, that's true. So there are independent mechanisms and there's also, I think one of the strongest areas of independent mechanisms are in gut Dysbiosis and gut function and the immune system and inflammation. There's a really interesting study that was conducted by Kevin Whelan on people with Crohn's disease and removing ultra processed foods, improving symptoms of Crohn's disease. So I think that that aspect is probably another clear area or certain emulsifiers in ultra processed foods might exacerbate gut health, especially in conditions like Crohn's or maybe inflammatory bowel syndrome. So yeah, that's another independent pathway. But yeah, so I've been mostly focused on the obesity side of things and trying to figure out, well, what is it about diets, high and ultra processed foods that might be driving this process? And that's kind of led us down to a couple of different areas. One was how quickly these foods are often been eaten. That tends to drive people to over consume calories. Folks like Kieran Ford and Kayes de Graaf have shown that textural based properties of these foods, they tend to be softer, easier to chew and swallow. Maybe by the time you've got the signal that you've eaten so many calories, it's already too late because you've eaten them so quickly. I think that's in the oral sensory properties of doing that I think is part of the story, but I think it's not the major story. I think the major story is the fact that these foods tend to be, they have their food matrix disrupted and they tend to be dried up. So in the ingredients that are used, drying them out is important for shelf life and microbiological safety. Right. Bacteria grow less well in dry environments. But in that process and removing the water essentially from the foods, you're also concentrating the calories, you're increasing its so called energy density. So the number of calories you get per bite of ultra processed foods tends to be quite a bit higher, even if the amount of fat isn't any different. Because fat is often considered because it has twice the calories per gram compared to carbs or protein. Often we think of high energy dense foods as being high in fat. Well, actually they can just be drier, less water, and that's another way to concentrate the calories. I think that's driving most of the effect. And we've designed a study where we have people consuming a DIET that's still 80% calories from ultra processed foods from this broad category. But we lowered the energy density of the diet, typically by diluting it with fruits and vegetables and legumes and things like that. But still having most of the calories coming from ultra processed foods. And, and when you do that, people eat many, many fewer calories and they don't over consume calories. So that's at least one factor. So thinking about how calorie dense the foods that you're purchasing are and how you're incorporating them into meals, I think is a really important consideration. The other property that we've kind of looked at is whether or not there are combinations of nutrients that exceed certain thresholds together that you typically don't find in nature. So called hyperpalva foods. Foods that are either high in fat and sugar or fat and salt, or carbs and salt both together. They also seem to drive people to consume more calories. And so by focusing on these two aspects, I think you can get at most of the effects of ultra processed foods on overconsumption of calories. So just a lot of things for policymakers. If you wanted to subcategorize ultra processed food, processed foods that are potentially problematic from a overeating standpoint, you should focus on those two properties, hyper palatability and calorie density. If you're a shopper, it's harder. Right. Cause then you have to take your calculator out.

Rich Roll (106:33)

Yeah, but from a consumer perspective, it's sort of like, was it Oliver Wendell Holmes who wrote the Supreme Court opinion about obscenity? It was like, you know it when you see it. It's like, it's impossible to define, but it's like everybody knows, oh, you kind of know it when you eat it. It's like, oh, can I, can I only have one and walk away? I think that's probably a pretty good rule for anybody.

Kevin Hall (106:55)

That is a pretty good rule.

Rich Roll (106:56)

But I would imagine there are not so great ultra processed foods out there that are counterintuitive. Like, oh, I thought this was healthy and now I just realized this is actually, it's so much more calorically dense than I realized. Or it has all these dark matter chemicals in it, as you say, or something like that that I wasn't even aware of.

Kevin Hall (107:18)

Or alternatively, there's probably also some foods that many people would all agree are ultra processed but are probably perfectly fine.

Rich Roll (107:26)

Like what would one of those be?

Kevin Hall (107:28)

Can you put me on the spot?

Rich Roll (107:29)

I don't know. But yeah, now I'm gonna recommending people.

Kevin Hall (107:32)

Eat, I mean, I think that many of the whole grain breads that you can get that have preservatives in them that would categorize it as ultra processed foods, that those would be some examples.

Rich Roll (107:42)

But the truth Is. And you know this like, you know, everyone's obsessed with protein. We didn't even talk about protein. That's like a whole podcast. Whatever. I know, but you know, we're so focused on the wrong things. It's like, you know, protein. I mean, like, we're not really, you know, having a crisis of people like not getting enough protein if they're just eating a variety of foods in their diet. But what we are having a problem with is people getting enough fiber in their diet. And if you were to just focus on that, like, how can I increase my fiber intake by, I don't know, 50% or 60 or 70% into the new year, wouldn't that solve a lot of problems for people? Or is that too reductive?

Kevin Hall (108:24)

It is too reductive. I'll tell you why. Because in our ultra processed diet studies, people ate the same amount of fiber because we gave them fiber supplements. And it didn't change the fact that they ended up.

Rich Roll (108:35)

It's interesting because I know the more that I like, if I make sure I'm eating a lot of fiber, then it just crowds out room for eating the other things.

Kevin Hall (108:43)

Yeah, you're getting it mostly from whole foods.

Rich Roll (108:47)

Yeah, I mean, when I say fiber, that's what I mean.

Kevin Hall (108:48)

That's what you mean premising on. So that's different. Right. And there's multiple forms of fiber. Right. But the way we sort of set it up in our studies, I mean, these folks are eating 50 grams of fiber a day in both diets. In one case, it's coming mostly from a fiber supplement. And yeah, you've got lots of ultra processed foods now that are adding fiber to a supplementary fiber to their sugar candy bars. Right.

Rich Roll (109:12)

Which is like greenwashing. I mean, you talk about that also. So it's sort of, that's problematic, the fortification of processed foods.

Kevin Hall (109:18)

Right. And we see the same thing with protein, we see the same thing with fiber. We see the same thing with people talking about low carb cookies and whatever. So they attach this something that in most contexts might be beneficial for the people who are trying to eat according to that dietary pattern. And then they've created these products that seem to fit within that dietary pattern based on some reductive thing like fiber or like protein or something like that. And so I think that that's kind of what we're seeing here. And in fact, that's kind of what we did in our study.

Rich Roll (109:50)

Right.

Kevin Hall (109:51)

We did the simple thing which is, oh, if I'm going to focus on fiber, I'm going to give people a fiber supplement. We'll get fiber up to 50 grams a day. And that's what they ate. And yeah, it didn't have the positive benefits that, what if they had to.

Rich Roll (110:02)

Eat celery or like just some, like, whole food.

Kevin Hall (110:06)

Right. Well, that's the point is that in the minimally processed diet, that's where they're getting the fiber. And in fact. Yeah, that's a big contribution. And it's correlated with things like energy density. Right. So these high fiber whole foods tend to have lots of water associated with them as well.

Rich Roll (110:25)

Calorically.

Kevin Hall (110:25)

Yeah, yeah. So these things kind of tend to go together. And so that's another problem in nutrition science, right, Is that you have these things like, food is not like one thing. Right. So you say, well, was it the fiber? Was it the low calorie density, Was it the phytonutrients? Was it.

Rich Roll (110:41)

You know, it's infuriating.

Kevin Hall (110:42)

It is.

Rich Roll (110:42)

There's no end to the amount. Whatever randomized control trial. You're never gonna be able to like, how are you gonna solve this problem?

Kevin Hall (110:49)

Well, I think the point is that we have to make incremental progress. I mean, one of the things we say in the book is nutrition isn't rocket science. It's harder because of these substitution problems. If you use real foods, you kind of gotta think about what have you replaced it with in your study. The, the fact that there's still all of these things about foods that we haven't even identified what's in them. The nutritional dark matter that you talked about, whether or not they're important for health is still an open question. So, yeah, I mean, you could throw up your hands and say we know nothing. But that's not true. Right? We do know a lot and we're making incremental progress. And I would say, given the anemic funding that nutrition science has had over the past several decades, we've actually made quite a bit of progress. But yeah, there's a lot more to do. And I'm excited about participating in that science in the future and figuring some of these things out. But we're not going to figure it all out. We have to kind of prioritize our list of topics of what's the most important thing to recognize. And I think that that's where reductionism can come into play. I'm intrinsically, as a physicist, a reductionist, thinking, well, yeah, if we could solve this part, we'll get to like 80% of the effect and then we'll Work on the rest of the 20, 20%, which will probably be five or six things contributing to that smaller effect and just sort of breaking out. What is the most important question and most important effect to kind of account for my view is that right now one of the most important effects that we need to understand is what is it about different food environments that causes people to consume vastly different amounts of calories? And how does that impact actually our biological systems that are regulating body weight? Because I mean, it's still just amazing to me. Right. And that we've seen this over and over again, not just in humans, but in animal studies over and over. You just shift their food environment in certain ways and without trying, they spontaneously choose to eat very different numbers of calories and regulate at a very different body weight. We need to understand that. And I think we're making progress.

Rich Roll (112:55)

I mean, that's consistent with the blue zones findings. It's not about individual choice, it's about where you live and is that environment conducive to health? Not just in terms of the food that, that is within arm's reach, but you know, is it a place where you have to walk a lot and you're engaged in some kind of low grade activity throughout the day and you're in a community and there's a faith based aspect to that. Like all of these factors, like you can change the food environment, but there's also the psychological factor and you know, like how you share love through food and all the, that's where it gets, you know, just, it just mushroom clouds into like a million variables.

Kevin Hall (113:34)

But if you, yeah, health isn't just about food and it's not just about metabolic health. Right. It's all these other things as well.

Rich Roll (113:40)

So if you were going to design like what is the ultimate study that you would like to perform if like funding was not an issue and it was all green lights all the way, what is the randomized control trial or what is the study that you would construct to help you answer the question that you're trying to answer?

Kevin Hall (113:55)

Yeah, I think it's multi again, it's multiple parts of research, the research community working together. Right. We don't have the ability in humans to measure the kinds of things that we can measure in for example, animal models and mice in particular to kind of manipulate neural pathways and measure specific populations of neurons and people are making a lot of progress there. But we do need the parallel human studies to measure and manipulate food environments in very controlled ways and observe how they affect, how do they affect different Kinds of people living with their families, for example, Example. And that's why what we were proposing was a facility to be able to conduct those kinds of studies in controlled manipulations of the food environment writ large. Not just the foods that you present to somebody on a plate, but the overall marketing of foods, the experience that they have on how frequently people are buying foods in restaurants versus preparing them themselves in their little local apartments, research apartments or something like that. How can we actually do studies where we can do very practical experiments manipulating the food environment to see what policies might actually be effective? Right. Like, we talk a lot about policies like menu labels and whatnot in front of packed labels, and we do a little bit of analysis of that, but we don't really do randomized controlled trials of that in small populations of people.

Rich Roll (115:20)

Does a warning label actually work kind of thing?

Kevin Hall (115:24)

Well, people do investigate some of those things in isolation. But what I'm talking about is, what if we had, like, a community of people where they would come and live with us for a month or two. Right. And we would switch up in a cafeteria, like setting the prices of different items or the quantities that we were giving to people, or change the formulations of those items and periodically measure physiological functions and biomarkers and whatnot, and really try to understand what changes in the food environment kind of in this broader sense, are actually contributing to people's behaviors.

Rich Roll (116:01)

That's almost like creating your own Truman show situation. Yeah. Sort of like these people where everything they interact with is a variable that you're controlling.

Kevin Hall (116:10)

That's right. But I think that the interesting thing is, I think that that kind of study would be a lot more humane than the kinds of studies that we've been doing so far, where people basically come and live in a hospital. Hospital ward for two months, sometimes isolated from their families. Right. But you could envisage a way of doing this kind of research that is actually more comfortable and enjoyable for participants and is developing a much richer data set that you could have, as, you know, you could clearly still have your primary outcomes as being. This is the main point of the experiment, but we're exploring a whole lot of other things simultaneously. Simultaneously in ways that were previously just free variables, and now we're able to kind of control them and get better answers to these kinds of questions and enroll different people from different patient populations and different ages and different parts and stages of life. Yeah, I think that it would just be an incredibly useful resource. And so the specific trial, I think, is less important than the ability to do these kinds things of studies. And what would we need in order to kind of do that? And we're not talking about billions of dollars, we're talking about tens of millions of dollars to create such a facility. The way I sort of think about it, kind of going back to my physics days is physicists don't have 20 different particle accelerators around the world, and everybody has their own little unit. They build a big one. And the people who have the best ideas for the best experiments basically submit grants to conduct those experiments at that facility. We need the equivalent of the big particle accelerator for nutrition research. And if we did, for human nutrition research, if we did, I think we would get answers to these questions a lot more efficiently.

Rich Roll (117:53)

There's gotta be a billionaire out there who's just like, yes, this is what I want. But for him, it's like buying a Starbucks. Here you go.

Kevin Hall (118:01)

You know what I mean?

Rich Roll (118:02)

I think we all want these answers, and I feel optimistic and confident that somebody's going to foot the bill for something like that, because these are that we all want. The work that you're doing is vital, and I'm certain that you're going to find your next spot. And I want you to be able to do all of this research because the world needs you, Kevin. And I appreciate you coming here and talking to me today.

Kevin Hall (118:27)

Thanks so much.

Rich Roll (118:28)

Yeah, so everybody check out Food Intelligence. I'll link it up in the show notes. And if anybody wants to learn more about you, where would you direct them?

Kevin Hall (118:39)

I guess website.

Rich Roll (118:40)

Kevinhallphd.com yeah, and more will be revealed about where you're gonna go next.

Kevin Hall (118:46)

Indeed. We'll figure it out.

Rich Roll (118:48)

Well, please come back and talk to me again. I really appreciate you coming here today.

Kevin Hall (118:53)

Thanks, Kevin. My pleasure. We'll do it.

Rich Roll (118:54)

Peace. All right, everybody, that's it for today. Thank you so much for watching listening. I really do hope that you enjoyed the conversation. To learn more about today's guest, including links and resources related to everything discussed today, visit today's episode page@richroll.com where you will find the entire podcast archive, as well as my books, Finding Ultra, the Voicing Change series, and the Plant Power Way. If you'd like to support the podcast, the easiest and most impactful thing you can do is free. Actually, all you got to do is subscribe to the show on Apple podcasts, on Spotify and on YouTube, and leave a review or drop a comment. Sharing your show or your favorite episode with friends or on social media is of course, awesome as well and extremely helpful. So thank you in advance for that. In addition, I'd like to thank all of our amazing sponsors without whom this show just would not be possible or at least, you know, not free. To check out all their amazing product offerings and listener discounts, head to richroll.com sponsors and finally, for podcast updates, special offers on books and other subjects, please subscribe to our newsletter which you can find on the footer of any page@rich roll.com today's show is produced and engineered by Jason Cameolo along with Associate Producer Desmond Lowe. The video edition of the podcast was created by Blake Curtis and Morgan McRae with assistance from our Creative Director Dan Drake, content management by Shana Savoy, copywriting by Ben Prior and of course our theme music, as always, was created all the way back in 2012 by my stepsons Tyler and Trapper Pyatt along with their cousin Harry Mathis. Appreciate the love, love the support and I'll see you back here soon. Peace Plants.