Most replayed moment: Carbs: the good, the bad, and the misunderstood | Tim Spector

Summary

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ZOE Science & Nutrition: Carbs – The Good, The Bad, and the Misunderstood

Guest: Prof. Tim Spector
Host: Jonathan Wolf (ZOE)
Date: March 17, 2026

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Episode Overview

This episode centers on carbohydrates: what they really are, the different types, their health impacts, and how we can make better carb choices without fear or confusion. Professor Tim Spector joins host Jonathan Wolf to bust the biggest myths about carbs, help listeners understand the difference between "good" and "bad" carbs, and offer practical strategies for making smarter carb swaps that suit real life—without sacrificing enjoyment. They even answer the viral question: does freezing your bread make it healthier?

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Key Discussion Points & Insights

1. What are Carbs, Really?

[00:47-03:20]

• Carbs are one of the three macronutrients (with protein and fat).
• Most foods are a mix of all three, not purely carbs.
• Carbs exist across a vast spectrum: from simple sugars (easily broken down by the body), to more complex starches, to fibers (difficult or impossible for our bodies to digest directly).
• Many people conflate "carbs" with "refined sugar" and overlook complex, fiber-rich, beneficial carbohydrates.
  • Tim Spector:
    “You don’t actually eat a carb, you eat a plant. … Most people think of carbs as only the sort of sugary end ones. They forget that a lot of the healthy carbs are these complicated fibers at the other end. So they throw the baby out with the bathwater. So, ‘I’m not having any carbs, it’s all rubbish, they’re all deadly.’ Well, that’s not true.” (03:08)

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2. Good Carbs vs. Bad Carbs — Practical Choices

[03:20-06:14]

• Tim’s choices: homemade sourdough with rye, German rye bread, whole grain pasta over white rice, diverse grains (lentils, quinoa, bulgur, pearl barley).
• More people are discovering whole grain alternatives and legumes as staple sources.
• Even beans and lentils, often overlooked, offer carbs plus protein and fiber.
  • Tim Spector:
    “Legumes are… I can’t get enough of those beans and lentils. And in every dish, I’m finding, as well as the classical ones, you know, we haven’t talked about the spinach and the kales… But I think it’s about the little swaps people can make to move away from the too easy to digest ones, the ones that give you those sugar spikes.” (04:41)
• Taste adaptation: switching to whole grain pastas and breads is easier than expected. Food tech is improving flavors and textures for these healthier options.

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3. Timing: When is the Best Time of Day to Eat Carbs?

[06:35-08:35]

• Studies show younger people metabolize carbs better in the morning.
• After age 50, timing’s impact fades; individual variance grows.
  • Tim Spector:
    “Some people might be better in the morning, some people in the evening. So I don’t think there’s a rule and I think you should follow whatever practice suits you and is likely to be sustainable. … So listen to your body, I think, is the rule here.” (07:40)
• ZOE’s dataset supports these findings: big differences by age.
• Key takeaway: Don’t stress about meal timing—listen to your own hunger and experience.

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4. Combining Carbs with Other Foods

[08:36-11:11]

• Eating carbs with fats and fibers slows sugar absorption, mitigating spikes.
  • Tim Spector:
    "If you eat it with other foods, you’re essentially wrapping the sugars in other foods that are harder to digest... These have been shown quite clearly to change the height of the sugar spikes, which will then reduce the consequences.” (08:42)
• Practical approaches: pair bread with cheese or nuts, pasta with olive oil or vegetables.
• Myth-busting: no need to obsessively separate or sequence foods—your stomach will mix them.
  • Tim Spector:
    "The stomach is like a washing machine where it churns it all up... If we’re eating them at the same time, this should solve that problem.” (10:09)
• But: you can't “upgrade” a highly refined carb (e.g., white bread) to the level of a whole grain just by adding fat or fiber.
  • Tim Spector:
    “No, you can’t put sprinkle on a turd. It’s still going to be a sugar and it’s always going to be better to have those whole grains because you’ve got the original nutrients of the carbohydrate.” (11:11)

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5. Individual Variation in Carb Responses

[11:40-13:11]

• Personal blood sugar responses can vary greatly—even between seemingly similar meals with the same amount of carb and fat.
• Adding fat does not eliminate sugar spikes for everyone—don't use fatty foods to "cancel out" carbs.
  • Tim Spector:
    “…It’s a mistake to think that you can have unhealthy carbs like a massive pizza base and just smother it with all kinds of unhealthy fats which might mask that sugar spike. … At six hours, your body’s still trying to get rid of those fats in your body. And can cause more problems than the sugar. So let’s not swap one problem for another.” (12:20)
• Mindset shift: treat high-carb, refined-carb foods more as occasional treats rather than staples.

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6. Does Freezing Bread (or Pasta/Rice) Make it Healthier?

[13:31-15:14]

• Cooling (and reheating) starches—bread, rice, pasta—increases resistant starch, acting somewhat like fiber and causing smaller blood sugar spikes.
• This effect is now well-supported by research.
  • Tim Spector:
    “…the starch, the sugars have become more resistant to digestion. That’s why they’re called resistant starches. And so they actually became more like fibre.... There have been a number of studies now showing quite consistently that you get a benefit on the amount of sugar that comes out of that food... I was very skeptical, but now I think actually it’s quite reasonable.” (13:36 – 14:46)
• Not always practical to batch cook or routinely chill carbs, but it’s a strategy for leftovers and could modestly improve carb health impacts.

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Notable Quotes & Memorable Moments

• On carb confusion:
  “Most people think of carbs as only the sort of sugary end ones. …They throw the baby out with the bathwater. … That’s not true.” (Tim Spector, 03:08)

• On ‘upgrading’ refined carbs:
  “No, you can’t put sprinkle on a turd.” (Tim Spector, 11:11)

• On meal timing:
  “Listen to your body, I think, is the rule here. Don’t get obsessed with it.” (Tim Spector, 07:40)

• On cooling carbs:
  “It’s sort of an extra reason to have those leftovers and do batch cooking for many people, because it will slightly improve how much … goes down to your gut and how much less is released.” (Tim Spector, 14:46)

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Timestamps for Key Segments

• 00:47 — What are carbs and why the confusion?
• 03:20 — What ‘good carbs’ does Tim Spector actually eat?
• 06:35 — Is there an ideal time of day to eat carbs?
• 08:36 — Mixing carbs with fat and fiber: does it matter?
• 11:11 — Can adding fat/fiber to refined carbs make them “good”?
• 11:40 — Why do some people spike from pizza even with fat?
• 13:31 — Does freezing bread (or cooling pasta/rice) really make them healthier?

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Summary Takeaways

• Don’t demonize all carbs—the “carbs are evil” idea is both simplistic and incorrect.
• Prioritize slow carbs: Think whole grains, beans, lentils, vegetables—complex carbs and fiber-rich foods support better blood sugar control and gut health.
• Swap, don’t subtract: Small changes like using whole grain pasta or sourdough rye can be easy and make a big impact.
• Feel free to experiment with timing and combos: Pay attention to your body, as there is no one-size-fits-all answer to carb timing or pairing.
• Chill your leftovers: Cooling cooked starches can reduce their impact on blood sugar, though it’s a marginal gain.
• Don’t expect to “hack” your way out of poor choices: The best approach is to build meals around minimally processed, fiber-rich carbs and treat refined carbs as occasional indulgences.

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Transcript

[A]

Hello and welcome to Zoe Recap, where each week we find the best bits from one of our podcast episodes to help you improve your health. Today we're talking about carbohydrates, pasta, potatoes, fruit and beans. Carbs crop up everywhere. However, few topics in nutrition cause us much confusion. Are they essential fuel or the enemy of weight loss? Should we cut them down or just choose our carbs more carefully? I'm joined by Professor Tim Spector to help untangle the truth and answer your biggest carbohydrate questions. Stick around to find out if freezing your bread makes it healthier. So what is a carb and what

[B]

is it that can make it unhealthy?

[C]

Well, a carb is a macronutrient. So in the old school world that we used to know, everything was divided into these three groups of proteins, fats and carbs. And most of the things we eat are mixtures of those rather than one thing. You don't actually eat a carb, you eat a plant. And that plant will have different amounts of proteins, fats and carbs in it. And within the carbs, it's going to have different types of carbs in it. And some of the foods we eat, which you say, oh, that's a carby food, like, say, bread, is also going to have some protein in it and a little bit of fat in it. So we tend to massively oversimplify, but that's what we've done in the past, mainly through ignorance, and the food companies have liked it that way because it's made it very easy to sell products to us. Now, I think we need to break down carbs into what they are, which they are essentially sugars that are either very simple, sort of moderately simple and really complex and long and hard to break down. So the simple sugars, like sucrose, you know, your table sugar is a very simple carbohydrates, very simple sugar. It means it only has a few bonds easily broken down and used by your body as energy. Then you've got the starches, which are slightly more complex storage forms of sugar, which are joined together by bonds which. Which can be broken down by other enzymes in your body. And every plant has these starches and we're designed to do them. So they break it down into simple sugars which are then released. Just takes a little bit longer. And then you've got the really complicated long sugars all joined together with lots of tight bonds that are called fibres. And these are sometimes really impossible to break down in the body, and only by the gut microbes sometimes, rather than ourselves, and they pass through the body. So you've got this complexity all the way from simple to very long and complex with very different effects on the body. So most people think of carbs as only the sort of sugary end ones. They forget that a lot of the healthy carbs are these complicated fibers at the other end. So they throw the baby out with the bathwater. So I'm not having any carbs. It's all rubbish. They're all deadly. Well. Well, that's not true.

[B]

So many questions. I just want to pick this one out first because it seems like directly relevant, which is, Tim, what are the good carbs that you eat?

[C]

Well, I eat as much as I can find, so basically, you name it, I'm trying to eat it. But I make my own sourdough bread and I make sure it's got plenty of rye in it. And if I find some nice German rye bread, that to me is a good carb because it's very hard to digest, so it's very slow to break down that rye. I'll have pasta rather than rice. So I still occasionally have traditional wheat pasta, but increasingly switching to whole grain, whole wheat pastas, which are better for me. And then you've got all these range of grains, so things like lentils, quinoa, bulgar wheat, pearl barley instead of rice. So they're sort of little ones that people don't often think about. I certainly didn't think about those 10 years ago. So increasingly I'm making these swaps as I'm trying to move away from the

[B]

traditional staples and whole grains and beans. I've heard you mention these are sort of the go to things, replacing the rice and the potatoes and the bread.

[C]

Yes. So we haven't mentioned legumes and beans, but absolutely they're a source of, you know, fats as well. So again, you know, what's a carb source? Gives you the energy, you know, you break down the sugars slowly, but it's also got protein, it's also got fiber. So legumes are. Yeah, I. I can't get enough of those beans and lentils. And in every dish, I'm finding, as well as the classical ones, you know, we haven't talked about the spinach and the kales and the whatever. So there, there, there goes without saying they're in there. But I think it's about the little swaps people can make to move away from the too easy to digest ones, the ones that give you those sugar spikes.

[B]

I have to say the thing that I found easiest is swapping regular pasta for whole grain pasta. And I know it's really easy because my daughter had a play date yesterday and I gave them pasta. We have whole grain pasta now in house. Gave it to her friend who's never had whole grain pasta before, I think, and she just ate it because, you know, it has cheese and whatever else and she's like delicious. So that one is so easy to make the change. And I remember being like, really? Oh, that's a disgusting idea. And I think within a week I was like, oh, it's completely normal. So I found that very easy. Whereas I think other things are obviously harder, right? To re engineer to eat less bread, for example, you have to really rethink the sorts of food. Cause you can't just get a, you know, if you're just always eating a sandwich, then that doesn't really work as much. And so some things are harder and some things are easier, Tim, to change.

[C]

Definitely, yes. I mean, so you've touched on some of them and some of these areas are new. So the foods are evolving. So you might have tried, you know, whole wheat pasta five years ago, but the new ones are actually tasting better. Similarly with the chickpea pastas or the lentil pastas, you know, they're getting better all the time, they don't fall apart like they used to.

[B]

Another question we had so much when is the best time of day to eat carbs?

[C]

Great question. The literature tells us that it's the mornings that are the best time that we metabolize better. So eating an identical carb meal we seem to have better control over it will bring those sugar levels down quicker, digest it faster than in the evening. Now the only caveat is those studies were generally done on young people, people 20 year olds. And when we looked at the Zoe data, we found that really this time difference pretty much disappeared after the age of 50. So the advantages for young people may be less relevant because young people really, apart from possibly mood changes, aren't really going to suffer many metabolic changes from having these spikes. Whereas as you get older, where it's more important, there seems to be more individual differences. So some people might be early, you know, better in the morning, some people might in the evening. So I don't think there's a rule and I think you should follow whatever practice suits you and is likely to be sustainable. And so that's why I still have most of my carbs in the evening, because I know it doesn't affect Me more than the morning, and it's when I'm hungrier. So my natural body tells me to do that. So listen to your body, I think, is the rule here. And don't. Just because some studies have shown in young people, you know, it is better if you can eat in the morning, that's fine, but don't get obsessed with it.

[B]

And you mentioned the, the Zoe data here. Is this a big data set that helps to inform what you're saying?

[C]

We've looked at thousands of people's data with Zoe who've done glucose monitors, and clearly this, this age effect and time of day is very different in young and old people.

[B]

Next question.

[A]

Does eating carbs with other foods at

[B]

the same time affect blood sugar spikes?

[C]

Absolutely, yes. So what we're doing, if you eat it with other foods, you're essentially wrapping the sugars in other foods that are harder to digest. So whether they're fibers that the body can't break down or it's encased in fats is really important. So that's why the importance of thinking about food in combination, thinking about what's on your plate rather than any one ingredient is really important here. So mindful eating, realizing that if you are going to have, for example, some bread, you've got no other, you've got no healthy bread, but you're starving, well, just have it with some cheese or try and balance these things up. So that. Or, you know, take it with a handful of nuts to give you some extra fiber. These have been shown quite clearly to change the, the height of the sugar spikes, which will then reduce the consequences. So it's not a absolute cure all for everything, but it will mitigate in a way, that sugar spike. So you can start to balance it

[B]

and do you need to sort of soak the food in that fat? So, you know, I'm thinking, because I sometimes feel like, oh, I've got that pasta, but as long as I pour loads of olive oil over it, like, maybe it's just gonna be like, slower to break down. Does it need to be, like, soaked in it? Or can I just have the two? Like one, you know, one mouthful and one or the other. But clearly it's hitting my stomach. It's not actually sort of encased.

[C]

I think as long as it gets into your stomach, it will. The stomach is like a washing machine where it churns it all up. So I'm not a big fan of people saying, well, I'm going to have my fats 10 minutes before I have my carbs. In order to get this, this response, I believe that generally our stomach is able to sort these things out. So if we're eating them at the same time, this should solve that problem. So I'm a bit against this obsessional eating that you have to divide your meal into 10 minute intervals. Having your cheese before you have your, and then your, your salad and then your potatoes, I think that's going a bit too far because for most purposes your stomach will treat it all the same.

[B]

And does eating like a sort of refined carb with some other food, does that suddenly make it as good as eating a sort of whole grain or unrefined carb in the first place?

[C]

No, you can't put sprinkle on a turd. It's still going to be a sugar and it's always going to be better to have those whole grains because you've got the original nutrients of the carbohydrate, you know, the bran, the ger, all these things on the casing that big food takes away in those foods. We were talking about the good carbs, then they will still have them. And you can't replace that just with a food tablet or just a bit of cheese.

[B]

I have to say, my own personal experience when I was doing the first cere studies with you, Tim, was that I was wearing this blood sugar sensor and I ate a big pizza. And obviously pizza got lots of cheese on it, right, so there's lots of fat as well as this, you know, sort of bread underneath, right, which is carb. And I think I had the biggest blood sugar spike in the entire two weeks from this big pizza. So it went off the roof, stayed high for so long, then finally collapsed later. And I know that I don't have very good blood sugar control, but it did definitely make me feel that I wasn't going to just be able to put a bit of cheese on like a piece of bread and magically not have any, any blood sugar spike. Is that very unusual response that I had.

[C]

Well, everyone's different, but there's plenty of people like you and we all respond differently to fats and sugars as we know. But I think it's a mistake to think that you can have unhealthy carbs like a massive pizza base and just smother it with all kinds of unhealthy fats and which might mask that sugar spike. But remember the fats. This is another podcast, but you know, at six hours, your, your body's still trying to get rid of those fats in your body. And can cause more problems than the sugar. So let's not swap one problem for another. You know, pizzas are fine, have them every now and again, enjoy it as a, as a treat. You know, maybe have your salad as your starter, which does help prime your, your blood sugar. But don't get too crazy on the extra fats.

[B]

I think one of the things that this has done is just change my mind to think about a lot of these things more like treats than as just sort of the, oh, you must eat this, because this is your source of energy and you need to, you know, if you're not eating lots of bread before you go out in the morning, then, you know, how could you possibly function in the day? But another question that came up surprisingly

[A]

often, does freezing your bread make it healthier?

[C]

Great question. And this is this whole question of what's called resistant starch. So bread is a good example, but it could be. The question could also be for pasta, could also be for rice. And it's. It comes from these studies that showed that if you. You cook these, these products and then the next day you put them in the fridge, then you reheat them, that they could be healthier because in some way the starch, the sugars have become more resistant to digestion. That's why they're called resistant starches. And so they actually became more like fibre. About 10 years ago, when I first looked at it, this was more theoretical than real. But the last few years, there have been a number of studies now showing quite consistently that you get a benefit on the amount of sugar that comes out of that food. And the sugar spikes. If you do this for rice, for wheat, for pastas. And I was very skeptical, but now I think actually it's quite reasonable. I'm not sure that I'd always want to be cooking everything two days in advance and leave it in the fridge, but it's sort of an extra reason to have those leftovers and do batch cooking for many people, because it will slightly improve how much, you know, goes down to your gut and how much less. Less is released. So, yeah, whether it long term, it's a technique, I don't know, but it's quite a fun thing to think about.

[A]

As you can imagine hosting this podcast, running Zoe, juggling family life, it all keeps me pretty busy. So I try as best I can to stay energized and show up well in all those parts of my life by fueling my body with the right food, by exercising, and by adding a scoop of Daily 30 to my meals every day. If you haven't heard of Daily 30 yet, it's the gut supplement designed by our gut health scientists here at Zoe. It's made of over 30 high quality hand picked plants including seaweed, fungi and different types of fiber. Better yet, it contains ingredients that support gut health digestion and energy, which is ideal for packed calendars and busy lives. Simply add one scoop a day to any meal for an extra boost of fiber and plant diversity. And because it tastes delicious on just about anything and adds a satisfying crunch, it quite quickly slots into your life, becoming a daily healthy habit you'll always have time for. By the way, whenever we talk about Daily 30 as a good source of fiber, we're required to say that it contains 4 grams of total fat per serving. Obviously that's all amazing healthy fats from plants, so order yours [e-mail] daily30. Thanks for listening and see you next time.