Diet vs exercise: which is more important?

Summary

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Podcast Summary: "Diet vs Exercise: Which Is More Important?"

Podcast: What's That Rash? (ABC News)
Date: January 13, 2026
Hosts: [Host not named in transcript], Norman Swan
Listener Questions: From Cathy and Rob

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Overview

This episode of "What's That Rash?" tackles the age-old debate: Is diet or exercise more important for your health? Prompted by listener questions about the real reasons behind Mediterranean longevity and blood glucose management, the hosts dissect scientific history, big studies, and practical advice, ultimately exploring whether this is an "either/or" question at all.

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Key Discussion Points & Insights

1. Setting the Stage: The Great Debate

• The hosts frame the episode using a playful "Would you rather?" format (01:01), choosing between never eating vegetables or never exercising again.
• Kathy's email notes how daily physical activity—not just diet—may be crucial to Mediterranean health (01:27), with Rob raising the specific case of blood sugar.

2. A Brief History of Diet (& Nutrition Science)

• The history of nutrition science is surprisingly modern. For most of human history, people had little choice in diet or exercise—they simply ate and moved as circumstance dictated (02:39–03:19).
• Historical Examples:
  • James Lind’s scurvy experiment with citrus fruit (04:02–05:49):

    "One of the earliest examples of a randomised clinical trial." – Norman Swan (05:49)

  • The origin of the word vitamin (Casimir Funk, 1910s) (05:52–06:33)
• Big Studies:
  • Framingham Heart Study (1948, Massachusetts) showed links between diet patterns and heart disease (06:33–07:03).
  • British WWII Rationing improved health by restricting unhealthy foods, leading to lower coronary heart disease rates (07:03–07:34).
  • Ancel Keys & The Seven Countries Study:
    • Lionized the Mediterranean diet, especially on the Greek island of Crete (07:40–08:17).

3. History of Exercise Science

• Ancient Advice:
  • Susruta (India, 600 BCE): First physician to prescribe moderate daily exercise, warning not to overdo it (09:21–09:54).
  • Ancient Greeks viewed exercise as key to spiritual life (10:13–10:21).
• Landmark Study:
  • Jerry Morris's London Transport Study: Conductors (who climbed stairs) had less heart disease than bus drivers (who sat), and similar findings with active vs. sedentary postal workers (10:41–11:24).

4. Comparing Diet vs. Exercise: Different Arenas

a) Weight Loss (11:46–12:36)

• Diet is the primary driver. It's very hard to out-exercise a poor diet.
• Quote:

  "It's very hard to do enough exercise that will compensate for swallowing calories in your diet." – Norman Swan (11:48)

• Exercise offers added benefit but is "inefficient" for burning enough calories to drive weight loss alone.

b) Cardiovascular Fitness & Heart Health (12:47–15:05)

• Exercise is crucial: Immediate and long-term benefits for heart and circulatory system health.
• Quote:

  "Exercise has an almost immediate effect on reducing your risk of sudden cardiac death." – Norman Swan (13:17)

• Effects are both quick (within days, if repeated regularly) and cumulative.

c) Blood Glucose Control & Diabetes Risk (15:32–16:28)

• Both matter: Diet is key (especially types of carbs), but exercise—especially muscle strengthening—improves insulin sensitivity.
• Quote:

  "If you exercise, particularly muscle strengthening exercises, you increase the bulk and metabolism of a highly metabolically active tissue, which is muscle, and muscle metabolizes sugar." – Norman Swan (15:47)

d) Behavioral & Social Factors (16:29–17:59)

• Exercise is easier to implement for most people, whereas diet change is harder due to habits and social/economic barriers.
• Quote:

  "It is easier to change your exercise focused lifestyle than your diet dietary lifestyle which is ingrained in habits." – Norman Swan (16:59)

e) Other Health Areas

• Osteoporosis: Exercise (weight-bearing) is more important than diet for prevention.
• Brain Health: Can't separate diet and exercise; both seem protective, and the evidence supports synergy.

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Memorable Moments & Notable Quotes

• On the futility of comparing marathons to ancient Greek messengers:

  "One guy ran, one guy ran, and then he died. I don't know why people now suddenly want to do marathons when the famous first marathon was pretty bad for that guy's health." – Host (09:08)

• On the fake rivalry between diet and exercise:

  "It's roughly a tie. And this was a false dichotomy anyway." – Host (18:07)

• On practical advice:

  "Make the majority of each plate filled with vegetables and the minority of the plate filled with protein and exercise. Get out there and do some any and then progressively increase it as time goes on." – Norman Swan (19:36)

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Key Timestamps for Important Segments

• 00:53: Would you rather never exercise again or never eat vegetables?
• 01:27: Listener Cathy’s Mediterranean diet vs. exercise hypothesis.
• 02:39: Brief history of diet, nutrition, and exercise choices.
• 06:33: The Framingham Heart Study and the birth of diet-pattern research.
• 10:41: Jerry Morris’s bus driver vs. conductor study.
• 11:47: Weight loss: Diet vs. exercise.
• 13:17: Exercise and immediate cardiac risk reduction.
• 15:32: Blood sugar and the metabolic role of muscle.
• 16:59: Why changing exercise is often easier than changing diet.
• 18:07: Acknowledgement of the false dichotomy—both are crucial.
• 19:36: Final actionable tips for listeners.

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Final Takeaways

• Diet and Exercise Are Intertwined: There’s no winner; both are essential for different facets of health. The "which is more important" debate depends on the health outcome you care about.
• For weight loss, focus on diet. For cardiovascular fitness and musculoskeletal health, prioritize exercise. Blood sugar and brain health both require both.
• Actionable Advice:
  • Diet: Make most of your plate vegetables, with some protein.
  • Exercise: Do any physical activity, and build up gradually.
• Practical Note: For most people, changing exercise habits is easier than changing dietary ones—but “best health” combines both.

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Listener Q&A Wrap-Up

• To Cathy: Not all Mediterranean food is created equal—look for traditional diets heavy on legumes and veg, not just processed meats (18:42–19:21).
• To Rob: Blood sugar control benefits from both diet (carb type) and regular exercise, particularly strength training (15:32–16:28).

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In summary:
Both diet and exercise matter deeply, and each shines in certain areas. Instead of choosing, do a bit more of both for immediate and lasting health gains.

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Transcript

[Host]

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[Narrator]

He was the man who stole the plans for the atomic bomb. A brilliant physicist, a devoted communist, a spy hiding inside the most secret project on Earth. This is the story of Klaus Fuchs, a man who believed he could serve two masters science and and the Soviets. To hear it, search for the bomb on the ABC Listen app.

[Host]

Norman, are you familiar with the game would you rather.

[Norman Swan]

No. What would I rather do?

[Host]

Well, basically, yeah, it's. Basically. Would you rather have feet for hands or hands for feet? That sort of thing.

[Norman Swan]

All right, so it's what you play with the kids in the car on the way to the coast, right?

[Host]

Yes, but I'm gonna do like a nerdy version of it with you today.

[Norman Swan]

Okay.

[Host]

Would you rather never exercise again or never eat vegetables again?

[Norman Swan]

I think I'd rather never eat vegetables again than stopping exercise.

[Host]

I think so too. Well, kind of, sort of. A little bit. That is a little bit. What's that Rash Is about today, which.

[Norman Swan]

Is the podcast where we answer the health questions that everybody's asking.

[Host]

Before we go on. Would you rather have food? Feet for hands or hands for feet?

[Norman Swan]

Feet for hands. For hands. I would prefer hands.

[Host]

Me too. Like a monkey.

[Norman Swan]

How would you eat? Right.

[Host]

Do something. Yeah, exactly. I would be able to climb trees. So much better. Oh, my gosh. I get so much better at climbing. Okay, let's go, let's go. Kathy has emailed in today saying, my husband and I have been sticking to a Mediterranean diet, ding ding, for over a year and recently had a holiday in Italy, I. E. A Mediterranean country. We had erroneously thought it would be easy to have a healthy diet in Italy, but now realise that this is not true. Kathy says, I would like to suggest that the reason people living by the Mediterranean Sea may have longer lives than most is the number of hills and stairs they have to climb in daily life and has little to do with what they consume. And Kathy says, could it be that exercise is more important than diet? Rob has a similar question, basically asking specifically about blood glucose levels. Diet or exercise. So today, Norman, we are doing the ultimate showdown. Diet V. Exercise. And imagine that this Mediterranean diet. Bell. Is sort of like a wrestling match bell.

[Norman Swan]

Yeah. Get it all out. Get it out of your system before we start.

[Host]

It's gonna be so many ding dings today. All right, diet versus exercise. Let's go.

[Norman Swan]

So why don't you give us a bit of history here? Cause we've never done this before in terms of nutrition.

[Host]

Oh, gosh, it's so interesting and it's also so recent. Well, I think the thing is that for most of human existence we really didn't have a lot of choice as to what we ate. It was like what can I kill or forage? What grows in my area? What have my ancestors gathered in summer so that we can eat in winter? The word diet.

[Norman Swan]

We also didn't have much choice about labor saving devices or motor cars.

[Host]

Excellent point. Diet and exercise was sort of. The decisions were largely made for us. I was interested to discover that the Greek word Dieta. Dieta. Greek scholars, please.

[Norman Swan]

Bucket of. I know.

[Host]

Please feel free to email me and tell me how much I mispronounce. Anyway, the word basically means way of living, the way you exist in the world. It's a very holistic view of diet as a lifestyle rather than just the food that you eat. Which I thought was interesting. But the actual like nutritional sciences era probably started in around the 1700s with a Scottish man of course, James Lynd.

[Norman Swan]

Yep. So people who know their history might know the story of James Lynd. One of the conditions that bedeviled long distance sea travel was scurvy.

[Host]

Yes.

[Norman Swan]

Bleeding teeth falling out.

[Host]

Scurvy is cooked. It's such a. So gnarly. It's like all your old wounds open up again.

[Norman Swan]

Indeed. And was a high cause. It was a significant cause of death. And you have to remember this was an era where illness and disease killed more military personnel than warfare. And so if you could actually find something that preserved the health and well being of your troops, you would actually have an advantage. In fact, it's a long story here, but it's for another day. One of the reasons the British were so successful at colonizing was that they had some secret medical weapons which others did not have, not against themselves but to protect their health. But anyway, that's another story. Nobody knew what caused scurvy but James Lynn wanted to do a randomized trial to find out.

[Host]

He have criticised in the past studies much larger than this, but he had 12 guys with scurvy. I suppose recruiting subjects was a thing as well. And they received different dietary interventions. And I don't know how he chose what to intervene with because one of the things was seawater, like making people drink seawater to see if it cured scurvy.

[Norman Swan]

Well, he concluded that being at sea your diet was restricted and therefore you might be taking things that would bring on scurvy or, or some people might be taking things that might prevent it or there was a deprivation syndrome going on. So he tried various dietary interventions Such.

[Host]

As seawater, as I said, cider vinegar, a mixture of garlic, mustard and horseradish, barley water, and crucially, citrus fruit. And that was what he demonstrated, obviously that citrus fruits could both prevent and cure scurvy, which laid the groundwork for later vitamin C being discovered.

[Norman Swan]

And again, one of the earliest examples of a randomised clinical trial. Wow.

[Host]

So the actual like vitamins themselves, that was the discovery? Well, at least it was named by a scientist called Casimir Funk. Coolest name ever, actually. If you think there's a cooler name in science than Casimir funk, email us thatrashbc.net.au I challenge Casimir Funk to out name anyone that you can give to us, but I'm happy to be proved wrong. Anyway, Casimir Funk was the guy who came up with the word vitamin because he thought it was an, an amine, a nitrogen compound and he thought it was vital. And so that's where we get the word vitamin from. Scientists later discovered that you didn't need an amine group for something to be a vitamin. They dropped the E, but the name otherwise stuck.

[Norman Swan]

Okay, so we're now arguing the case for diet being the most important thing. So let's just do a bit of rah rah for diet here. And one of the rah rahs is the framium heart study, which started in 1948, forming thousands of people in the town of Framingham in Massachusetts.

[Host]

Right. So this is, I think those big diet pattern studies, like not just focusing on a single nutrient like a vitamin, but diet patterns. That's a very like mid 20th century onwards thing. It's pretty recent I think really.

[Norman Swan]

So they showed, you know, high saturated fat diet, the western diet was bad for you. Really interesting studies again pushing the diet side of this story is that when they developed rationing in the uk, they used a leading nutritionist, I think she was at King Cambridge University, designed what was considered then to be a healthy diet. And in fact it was quite a healthy diet. And rationing restricted unhealthy parts of the diet. And things like coronary heart disease did decline during the war.

[Narrator]

Right.

[Norman Swan]

Because rationing put you on a healthier diet. And then there was Ancel Keys.

[Host]

So Ancel Keys is one of those people whose name, you know how there's this sort of sense that everyone's born already knowing all the lyrics to Beatles songs. I feel like I kind of knew who Ancel Keys was before I even knew who he was. And one of the things that he is famous for is what's called the seven Countries study. So he basically Looked at, it was kind of.

[Norman Swan]

He rang the bell for the Mediterranean.

[Host]

Oh, he sure did. He basically was the guy who was first, like, Mediterranean diet, but it was.

[Norman Swan]

Mostly Crete that he studied. It was the Greek island diet that he particularly lionized. A lot of the idea about cholesterol really consolidated in Ancel Key's work, although really it was there in the Framingham study as well.

[Host]

And what these studies are looking at are basically mortality and death. So, like, what do you eat and how do you die? And so to sort of come back around to this, like, diet versus exercise thing. Turns out diet's pretty important. So I don't know how many points that tallies up on the side of diet, but there's a few there.

[Norman Swan]

And one of the themes that we'll come to in a minute is it depends on what you want and what you're trying to achieve whether diet or exercise is going to work, not just our personal preferences. So let's go to the exercise side of the equation. Does it, you know, how does it measure up? Is it going to win the prize?

[Host]

Well, let's have a look. So, I mean, it's similar. I mentioned some pretty recent stuff with diet and nutrition. Obviously, we've known that food's important for our health for centuries, decades, millennia.

[Norman Swan]

And speaking about the Greek island diet, you know, they ran a lot. You know, these marathons taking measures.

[Host]

One guy ran, one guy ran, and then he died. I don't know why people now suddenly want to do marathons when the famous first marathon was pretty bad for that guy's health.

[Norman Swan]

But that was because they killed a messenger. He had a message, and the person who received it didn't like it that much anyway.

[Host]

Anyway, let's talk about exercise. We have known that exercise is good for you in moderation for a while. Susruta from India is one of the first known physicians to prescribe moderate daily exercise to his patients. This is 600 BCE, so a little while ago now, but the paper says it should be taken every day, but only to half extent of his capacity. Otherwise it may prove fatal. I mean, that's technically correct. I don't know about the half your capacity thing, but if you do exercise too hard, you could die.

[Norman Swan]

Well, if you've already got heart disease, but it's actually quite an unusual complication of exercise, you can go pretty hard.

[Host]

The other thing that Susruta said was diseases fly from the presence of a person habituated to regular physical exercise. Norman Swan, fact check, please.

[Norman Swan]

Absolutely, 100%. And I use the ancient Greeks as my other reference here.

[Host]

Okay, please explain.

[Norman Swan]

Well, they used to like running around with no clothes on and lionized. Exercise is a very important part of spiritual life.

[Host]

I mean, in terms of communicable diseases, I think if you were running around naked, people would give you a wide berth and you're probably less likely to.

[Norman Swan]

Catch something from true.

[Host]

Actually, this is. Did you sort of like pepper the research document with just Scottish guys? Because there was another Glaswegian who is important in the exercise health story.

[Norman Swan]

Yeah, this is Professor Jerry Morris, who ended up in London, but yes, came from Glasgow. And he did this fascinating study comparing the risk of heart disease between drivers of double decker buses and the conductors who would run up and down the stairs taking the fares.

[Host]

We have talked about this one before.

[Norman Swan]

I think we have. And he found that the drivers had much higher rates of heart disease than the conductors who climbed the stairs. He also did it in postal service. Postmen who delivered the mail on bike or foot had fewer heart attacks than sedentary men who serve behind postal counters or as telephonists or clerks. So, you know, if Jerry was in the studio, he would be pushing exercise really strongly.

[Host]

So that's sort of, I guess, a potted history of the origins of the science of diet and exercise. Lots of asterisks at the end of that. We've cut out a lot of stuff. So now I really think if we're gonna compare the two, we probably need different arenas for this. Cause as you said before, it depends what you want. Whether diet or exercise is more important.

[Norman Swan]

Well, let's start with weight loss.

[Host]

Okay.

[Norman Swan]

It's very hard to do enough exercise that will compensate for swallowing calories in your diet. So if what you're wanting is weight loss, you've actually got to change your dietary pattern and reduce the intake of cheap empty calories, for example, so that you are tailoring your energy intake to your energy output. Now, once you do that and you add exercise, you do get added benefit, but very hard to lose weight if you're relying on exercise. It's just so inefficient in terms of burning calories. That's not what you get from exercise. You get a lot more from exercise than weight loss. So diet wins 1 nil on weight loss. Okay, so weight loss, it's not quite 1 nil. It's like 1 versus 0.2.

[Host]

Very scientific, very specific. So weight loss, really important for some people, less relevant for lots of us. What about other factors or facets of health?

[Norman Swan]

What about, let's take cardiovascular fitness.

[Host]

Yes, you took the acronym right out of my mouth.

[Norman Swan]

So cardiovascular fitness, it's exercise.

[Host]

Okay.

[Norman Swan]

There's really, you know, strengthening your muscles, cardiovascular health.

[Host]

Do you mean like, do you, when you say cardiovascular fitness, do you mean.

[Norman Swan]

Like your heart, your cardiorespirit fitness, your cardiac fitness, Effectively your ability to exercise without getting breathless lift things, things have good muscle strength.

[Host]

How does that translate to cardiovascular risk of something like a stroke or a heart attack?

[Norman Swan]

So exercise has an almost immediate effect on reducing your risk of sudden cardiac death. People talk about sudden cardiac death being a problem with exercise. In fact, exercise reduces the risk of sudden cardiac death and it does it very, very quickly.

[Host]

I'm surprised to hear that. I think, I sort of thought it was like you sort of playing the long game. You're laying a lot of groundwork throughout your whole life so that you don't get a heart attack when you're in your 60s or something like that. How quickly are we talking?

[Norman Swan]

There is truth to that, but you get very immediate effects of exercise at a moderate level. I mean, why do we do it every day or two? It's because the immediate effects tend to disappear after a day or two and you've got to do it again for them to come back. So there are long term effects in terms of muscle strength, of improved cardiac output, the resilience of the cardiovascular system. But what happens when you take exercise and is that your blood vessels expand, your blood pressure goes down, it goes up initially but then goes down, your pulse rate eventually drops. There's all sorts of things, your sympathetic nervous system gets settled down. So after exercise your body goes into this state, which is actually a state of reduced cardiac risk. But you've got to repeat the exercise in order to gain that benefit. So repeated exercise is for both its immediate effects and its long term effects. By the way, it's similar for smoking. When you stop smoking, the effects happen within hours, days and weeks, not necessarily years. There are benefits over time. So diet does have an effect on cardiovascular risk, but it's hard to change your diet quickly enough to have that effect. Where we're coming to with all this is exactly as you say, it depends on what you want. So if you want cardiovascular protection, you've got to do both.

[Host]

Okay, so we need to touch base on our score, which is very scientific and not at all imaginary. We had 1 versus 0.2. We were talking about weight loss before, 1 being diet and 0.2 being exercise. What are we up to when we add in cardiovascular health?

[Norman Swan]

I think that we're onto 2o really with a bit of 0.02 there for exercise. So in the end it's pretty equal.

[Host]

Well, the question that Rob asked was specifically about blood glucose control. What do we know about that?

[Norman Swan]

A lot of that is diet, but some of it is exercise too. Because if you exercise, particularly muscle strengthening exercises, you increase the bulk and metabolism of a highly metabolically active tissue, which is muscle, and muscle metabolizes sugar. And muscle is very important in terms of sensitivity of the body to insulin. So if you change your diet to one which is higher in complex carbohydrates, et cetera, you will help your blood sugar, but you will also help your blood sugar in the long term by exercise, by strengthening muscles and by having strong muscles, because strong muscles prevents your blood sugar spinning out of control.

[Host]

Okay, so score check.

[Norman Swan]

We're still, now we're at three all really, aren't we roundabout? Thereabouts.

[Host]

Sure, why not? So, okay, so we, I asked you before if you'd rather never exercise again or never eat a vegetable again and you said you could do without veggies, but you couldn't do without exercise. So your team exercise, I'm guessing behaviourally?

[Norman Swan]

I think I am, yes.

[Host]

Yeah, me too.

[Norman Swan]

It's hard to control my outer control appetite. That's the problem.

[Host]

Well, it's also like it's easier to find an hour to go and do something active than it is to like coordinate all of the different food and food environments that you find yourself in day to day.

[Norman Swan]

Correct. And that's one of the issues here is that it is easier to change your exercise focused lifestyle than your diet dietary lifestyle which is ingrained in habits. Your appetite control is set when you're in the adolescence and sometimes it's really hard. And also if you don't have as much money in your pocket to buy healthy food or you're living in a part of Australia where healthy food is harder to get or more expensive then getting out and exercising is a really important thing to do. Now there are other things where exercise is really much better for you and that is for example in the prevention of osteoporosis. Of course you want weight bearing exercise, you want high impact gravity based exercise that stimulates the growth of your bones. So that is much more important than your diet when it comes to osteoporosis, for example. And then there's brain health. And the evidence on brain health is that you can't separate diet from exercise. That these factors which both protect the brain and put the brain at risk work together. So you can't separate the two.

[Host]

Well, that's probably lucky because it sounds like it's roughly a tie. And this was a false dichotomy anyway. I think it was completely imaginary, but a good challenge.

[Norman Swan]

Thank you very much.

[Host]

I think so, too. And there have been actually been studies looking at what we kind of do with this information about the fact that some people can only do one or the other. And people have looked at what is easier to do. And no surprise, exercise is easier for people to implement than diet change, as you and I have already established in our N equals 2 study.

[Norman Swan]

It is.

[Host]

So, Rob, Cathy, what do we say to Rob and Cathy, you were going.

[Norman Swan]

To the wrong restaurants in Italy.

[Host]

Where would you recommend?

[Norman Swan]

Well, that's the whole thing.

[Host]

I'm from the coffee gelato place.

[Norman Swan]

It is the whole thing about the Mediterranean diet is that the diet changes around the Mediterranean. And Ancel Key's work and others focused on the Greek islands. So that was the Greek island diet. And sure, you go to Italy and you eat processed meats. It's not a very healthy diet. But the traditional Italian diet is pretty healthy and not too different from the Greek island diet. You're getting your protein from legumes. You're not eating that much red meat, and you've got complex carbohydrates. So there is a version of that. But when you're there on holiday and stuffing your face with prosciutto and mortadella.

[Host]

Okay, so final word, Norman, is question without notice if someone's listening, going, okay, diet, exercise, both important. What do I do today? What's one thing that I do today in each of those columns to improve my what do you recommend?

[Norman Swan]

Make the majority of each plate filled with vegetables and the minority of the plate filled with protein and exercise. Get out there and do some any and then progressively increase it as time goes on.

[Host]

Add a serve of veg, add a serve of exercise. And add an email to thatrashvc.net au with your health question. Rob, Cathy, thank you both so much for your questions today.

[Norman Swan]

No, we want some special feedback from you.

[Host]

Right. So this is usually where I would say what your feedback has been. Well, this is a note to say that we are now back. We're back from holidays. We are reading and responding to your email. So please send in your questions for 2026. And like I said a few weeks back, I want to know what has been said around the dinner table over the holidays. Send us your slightly unhinged relatives theories about health, your questions that you want us to tackle.

[Norman Swan]

Uncle Arthur on vaccines. Love to hear it.

[Host]

And we will t to those questions in the coming months.

[Norman Swan]

See you next week.

[Host]

I'll see you then.