Instant Genius - Calories, with Dr Giles Yeo

Episode Date: August 1, 2021

Trust Me, I’m a Doctor’s Giles Yeo tells us about the history of calorie counting and whether there’s such thing as ‘good’ and ‘bad’ calories. Once you’ve mastered the basics with Instant Genius, dive deeper with Instant Genius Extra, where you’ll find longer, richer discussions about the most exciting ideas in the world of science and technology. Only available on Apple Podcasts. Produced by the team behind BBC Science Focus Magazine. Visit our website: sciencefocus.com Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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delivering digital precision with analogue warmth. So you can experience exceptional sound at home. Music just as the artist intended. Visit name audio.com. to learn more. Hello and welcome to Instant Genius, a bite-sized masterclass in podcast form. I'm Jason Goodyear, commissioning editor of BBC Science Focus magazine. In this episode, I talk to Trust Me, I'm a Doctor's Dr. Giles Yo, about his new book,

Why Calories Don't Count. Okay, so your new book is Why Calories Don't Count, and everyone's going to be, everyone listening, I'm sure they're aware, and they've seen the labels on food packets and drinks, cartons, etc. Even on some restaurant menus now, about the... nutritional value and the caloric content of food. But I think we're really, first question we should be asking is when we're talking about a calorie, what are we talking about? Because it's not as simple as it might seem at first, is it? So, okay. So in terms of a calorie, a calorie is the amount of

energy it takes to raise one liter of water, one degree Celsius at sea level. That's a food calorie. There is a smaller calorie called a heat calorie, and there's one thousandth of a food calorie. But the calories we hear about, and we talk, when I say the word calorie, one liter of water, one degree Celsius at sea level. And so that is what an actual, that's what the calorie is. And so you might think, well, how can it not count, given that it's a unit of energy? It should be exactly the same. And that's true to an extent. But they're all equal once you get them into your body as a little proof of energy.

and your body can actually use it. But our body has to work in order to extract calories from food. So we eat food, not calories, and then our body then works to extract calories from the food. So in the book, you mentioned something that you call a calerific availability. And that is key when we're talking about calories in terms of nutrition. So could you just run through that idea for me, please? Okay, so caloric availability is the amount of calories that we can actually extract through the digestion and metabolism process compared to the total amount of calories actually stuck in a food. So I think the most obvious example that we might encounter on a day-to-day basis

is if we eat sweet corn, so corn on the cob, and then the next morning we kind of peek in the loo and we see that we have not absorbed all the sweet corn. So that's a situation where clearly, because of the presence of fiber and any other number of things, we are not able to digest all the sweet corn. So that's caloric availability. So if you have 100 calories of sweet corn, you're not going to absorb 100, 100 calories. So that's the concept of caloric availability. What can our body take out of the food? Yeah. So just moving on from that,

because this can get very complicated, very quickly, can't it? So very simply, how do we extract energy from food? Okay. So there are two stages. I think the first stage is what most of us, well, I'd like to think most of us understand what are this, is digestion. And so there are two elements to digestion. There's mechanical digestion, and that is the chewing bit and the little washing machine bit that the stomach makes called peristelsis. So physical agitation. But the vast majority of digestion, which happens largely in the small intestine,

is a very long chemical reaction. And so your stomach and other parts of your body squirts enzymes into the intestine, which then begins to slowly break down food. So that's the first bit, okay, because then the three macronutrients, for those of you who have heard it, so protein will be broken down into amino acids, starches or carbohydrates will be broken down into sugars, or you can eat sugars, obviously, by itself, and fat will be broken down into fatty acids. And so these cross across the intestinal wall, the gut wall, and into the blood.

Now, people think that, well, that's it. That's our fuel. And it isn't because those amino acids, fatty acids, and glucose, those sugars, are simply transportable units of nutrients. Then they're transported by the blood into your cell or your liver or some organ. And within the cell or within the organ, those nutrients are then metabolized into the actual energy that we use. So there are two steps, digestion and then metabolism. And each cost energy, and we lose some of the calories at each of those two different stages. So then essentially,

what we can say then is, even though as a sort of raw unit of energy, calorie, is all the same, but not every calorie that we consume as food is equal. That's correct. So I'll give you the one which makes the biggest difference. And that's going to be protein. Now, a calorie of protein will make you feel fuller than a calorie of fat than a calorie of carbohydrate in that order, okay, even though it's a calorie. And there are any number of different reasons for that. The first is because protein is chemically the most complex to take apart in digestion, and is also chemically the most complex to take apart in metabolism. Okay, it takes a lot of energy. So we now know that for every 100 calories of protein that you eat,

you will only ever absorb, on average, 70 calories, which means that for every 100 calories of protein you eat, 30% of the calories are used to deal with protein. And what you see in the back of the pack, therefore, just on the protein calories in and of itself, is going to be 30% off, 30% wrong, you know, just because of that. When it comes to these labels, like you just said there, so this has got a really interesting history, isn't it?

going back to, you know, a century plus. Century plus. So the labels, so what you see on the side of the label, all the calorie counts that we see, are based on numbers generated by a chap name Wilbur, Professor Wilbur Olin Atwater, who was a professor of chemistry from Wesleyan University in Connecticut, in the United States.

And it was work that he did, actually, between 1880 and 1900. So yes, so more than starting 140 years, ago to 120 years ago. And so what Atwater realized was he realized the sweet corn effect. Okay? So he was throwing, well, how much, you know, how much calories do humans actually absorb? So what he did was he measured the total amount of calories in food. Now, how do you do that? You do that, even today, using something called bomb calorimetry. And that's a situation where you burn food in a sealed container. And because, as I said, a calorie is the amount of energy it takes to raise one liter of water to 1 degrees Celsius, if you have a known

volume of water surrounding this sealed container and simply put a thermometer into the into the water bath. Then the temperature rise in the water equals the total number of calories in the food. This is called bomb calorimetry. So what Atwater did was he measured the caloric content of thousands of different kinds of food, like over 20 years, okay, all the foods you can think of. He then, and this is the bit, by the way, think about this before you complain about your job again. So he then fed these foods to human beings, and then burnt their poop. So in other words, so what came out the other side? For 20 years he did this.

He then subtracted what they ate from what they pooped out, and that was the amount of calories they absorbed. And based on that, he came up with the so-called at-water factors, which is nine calories for every gram of fat, four calories for every gram of protein, four calories for carbs. and every single calorie count you see on the side of the packet is based on this. There is, and now when you listen to this, you go check, there is a little bit of woggle, wobble because of the way people calculate how much protein there is in the food. But it's going to be plus or minus a few percentage points from 9-44.

Those are the at-water factors, which are over 120 years old, and we are still using today. So then sort of following on from that chronologically, a bit after this, the idea of controlling your weight or your diet by counting calories emerged and became popular. That's right. And this came from a doctor, and she was unusual in a number of different ways. But the most unusual element of it was that she was a medical practitioner, an actual physician, a doctor, around the time of World War I. Now, this was only 10 years or so since women were allowed to be doctors at all. So her name was Lulu Hunt Peters. She was a, shall we say, say larger lady who was concerned about her weight, but she was scientifically trained, and she came

across the work of Atwater. And so she thought, well, okay, and she understood physics. And she says, well, how do I get myself to eat less? Rather than imagining what I'm going to eat less, she began to try and devise how much less she needed to eat. And so she was a syndicated columnist, so she was a medic and a syndicated colonist in which she was just talking about this. And she eventually wrapped the whole thing up into a book where, in effect, she gave actionable information. She says, well, here is 100 calories worth of sausage, worth of bacon, with of bread, whatever. And so people, this was, the book was targeted to words, I have to say, white middle class women at the time around World War I. And this is how much you would need to eat if you are larger than you were and needed to be.

And so you could count the calories than to lose the weight. And she was the first calorie counter. fascinating woman. The book was Luluhan Peters, fantastic read, still available on all the various online bookshops. Very funny. But she, in effect, raised the idea of when you talk about calories,

you talk about food. She started the weaponization of the calorie. So you said there that she was perhaps a slightly larger lady, and she actually followed her own advice. She did. Successfully. She did. So she was.

When I mean a larger lady, I think she was something close to 210 pounds or something like that. Okay, so a large lady, right? Because I'm 175 pounds, for example. And she managed to drop more than 50 pounds. She dropped herself to about 160 pounds, 100 and something. So I don't think she ever became skinny, but that's, you know, we're all different sizes. But, yeah, she followed her calorie counting regime. And this is what she wrote about, right, in her book.

And, yeah, she ended up losing 50 pounds in weight. So how popular was her book when it was printed? It was a bestseller for nearly five years in row. So it was a weird time in the world. It was just coming to the end of World War I. And what happened was as she wrote the book, she kind of pushed it out. She then traveled to the Balkans to work for the Red Cross, okay? In military, looking after the patients.

And she was there for five years during the recovery post-World War I. And when she came back, she had found that her book was, and, you know, certainly very, very close, if not at the top of the New York Times bestseller, for five years for a very, very long time. And so millions of copies, millions of copies at a time when the diet industry was, she was probably the beginning, I would argue, of the diet industry. So you mentioned that, she had a list of a hundred foods, say, with the proportion to 100 calories portion of a tomato is this and that.

But if we break that down, you know, our, if we, we got worse calories in a donut, better calories in a carrot? You know, how does that break down? So are all foods equal? They're not. And they're not because, look, 200 calories of chips is clearly twice the portion of 100 calories of chips. Okay? So clearly that I'm not saying anything else. But so is 200 grams of chips weighing more than twice more than 100. grams of chips. Now, we would never in our life, I would like to think, say that well, I've had 100 grams of chips

and I'm going to compare it to 100 grams of carrots, right? Because they come in different densities, they're different things. What can you actually do with it? Now, the calorie is only ever so slightly better than the gram of food, but it's the same analogy. Because your body has to work to differing amounts,

comparing calories across different foods doesn't make a lot of sense because we eat the food and not the calories. So one thing that people often say as well is, what's the difference between eating raw food and cooked food in the way that you can absorb the energy, the calories from it? So what cooking does is an extension of your digest.

Well, cooking clearly also killed parasites and things, all right, and probably made it more palatable. But critically, cooking was an extension of your digestion, digestive system. It began the digestive process, but outside. And so I think people were saying that the whole, when humans, whichever homo species, first controlled fire, and they then began to put a proto-potato and a piece of venison into the fire, A, it tasted better and smelled pretty good, they were then able to extract more calories for exactly the same amount of work. So all the work they went into to tracking down the antelope and pulling it down and digging up the potato,

suddenly because of cooking it and it did some of the digestion for them, they were able to get more energy from the food. And actually, that was one of the drivers of getting the human brains bigger and being able to begin to think. Let's put it this way. It's pretty difficult to contemplate the cosmos if you're hungry. So once you actually are less hungry, you're able to think about other things such as quantum physics. So sort of moving on then to how we use this So there's one section of the book in which you say it takes less than 100 calories to boil one litre of water. That's it.

Because one litre, one Celsius sea level. So actually, and if you go down and fill your kettle, a litre is about average. We might fill up a kettle and take, what, takes 90 seconds? It only takes 100 calories. A hundred calories is one, roughly speaking, one chicken's egg. So there's only five, and a half liters of blood in us, roughly speaking,

and we eat 2 to 3,000 calories of food a day. So how come we're not boiling? And the reason is because that we... Now, if we took the food, all the food we ate and stuck it into a bomb calorimeter, okay, desiccated it, pressurized it and burnt it, it would boil, right? 20 liters of water or whatever.

But because our body takes the food into individual nutrients and then breaks them down into little units of energy, used to make ATP, actually, these little units of energy. The ATP becomes ADP, poof, energy, then it recycles. So it uses it in little transportable little compartments of energy. It parcels the energy out, which is why we don't end up going up like a Roman candle. So obviously, we've established already pretty quickly that there's some flaws with this calorie, at least with the labelling system. So what enabled it to persist for so long, do you think? That's a very good question,

just to be clear, what I talk about in this book, I didn't invent, right? It's not like I sat there and I worked it out. I looked at the literature. I looked at it and it was all there. In fact, some guy called Livesey in 2001 tried saying this in a, he was a part of a nutritional think tank, I think from Norfolk of all places. I didn't realize there were think tanks in Norfolk, but there are. So anyway, so he, no, I don't want to be rude about Norfolk. So anyway, so he suggested this very thing, talking about, net metabolizable energy. So talking about the exact process I'm talking about, you have digestion, then you have metabolism, and what you actually end up using. And he was ignored. He was completely ignored by the very nature that we're here chatting about this. And when I tell people about this, people have no idea that this occurs. Now, when you speak, let me tell you who knew. Okay, the people that know, oddly enough, are the farmers. So in particular the ones that raise livestock. Because the original concept of the calorie and food was actually designed for farmers to try and optimize the amount of feed they were going to give to cattle or sheep or chickens to maximize the production of meat. Because look, this is after all their livelihood.

And so the farmer would be able to tell you chapter and verse about this, whereas all the rest of us are eating the food are just not able to. So the answers I don't know. I think it was ignored. Is it because it's a pain in the backside to relabel? I don't know. But it's been ignored. And it's pretty much worldwide, isn't it? This calorie labelling system.

I've definitely seen it in other countries. Yep, exactly. The labelling, certainly in prepackaged food. And given that is multinational conglomerates making these foods, all of the calorie counts will be based on exactly what we talked about, 944. So then just sort of going back to actually expending energy. So this sort of goes hand in hand with diet, you know, physical activity and exercise. So are some people just naturally better at burning calories?

They burn them all. You often hear people say, oh, I've got a slow metabolism. I just have to look at a slice of pizza and I'll put a stone on. Other people, they can eat burgers, chips, whatever they want and they never seem to put any weight. Now, is there any truth to that? Okay, so actually, the biggest effect on your energy expenditure, on your metabolism, it's going to be your body size. The larger you are, the more energy you'll burn. People go, no, that's not true.

I thought the people who are bigger have lower metabolisms. No, it's not. So the analogy is that a little mini-couper, small tiny car, will always have a lower fuel consumption than a big SUV. Okay, so the small car might look zippy and going around, but they'll always use less energy. That being said, yes, there are going to be people who are more efficient or less efficient in dealing with calories than other people. The difference is just not as great as some people might imagine. But yes, it is true that some people eating exactly the same amount of food will gain

or will gain more weight or less weight than me. but the effect of food intake, putting it at the top hand, the top end over here, will always surpass the differences between you and me, for example, in our ability to partition nutrients, is the terminology, burn or store. So you were talking about size there. What role does body composition play, like somebody's muscle mass or their body fat percentage? So all parts of your body, bar your things like your,

fingernails. So all parts of your body that are alive will need metabolism because it needs energy in order to survive. But depending on their role, they are more metabolically active than others. Now, fat is not simply cushioning which you sit on. It is an endocrine organ. It does release, it does actually release hormones and things. So it does have obviously have metabolism. But muscles, for example, and the liver, so these are very, very highly metabolically active tissues because your muscles move you and your liver is detoxifying your blood all the time. So these will use more calories. So for a given, for a person of exactly the same weight between, say, a sumo wrestler or a rugby player,

okay, this is where BMI falls down. So where you have a sumo wrestler or rugby player who is, I don't know, 150 kilos or whatever, whereas they're going to be a lot of muscle. Whereas if you take 150 kilo Joe Schmo, that is far less muscle and far more fat, then the big rugby player is going to have to eat a lot more, even not counting the exercise, because they have more muscle mass, they definitely will have a higher metabolism.

So sort of following on from that, another common thing that you often hear people say is, you know, they've made a new year's resolution. They're going to go, let's say, running three times a week in order to lose a few pounds. And they start doing it, but they don't lose any weight. what's going on there? Where are they going wrong? So I think what is known now is that exercise per se is not a particularly useful tool for weight loss.

Now, then you might think, well, how can that be the case? Because it's physics, right? In, out. And so the Tour de France has just finished, probably just at the end of last week or something. And these guys have to eat 5,000 calories a day for three weeks in order to complete the race, but yet they lose weight. Okay. So clearly, if you exercise enough, you will lose weight. The problem is for mere mortals and for the vast majority of human society, bar professional athletes and Olympians and things, we don't exercise enough to lose to lose weight. Because when you exercise, two things happen. You become hungry. And so you actually, you actually, and actually our ability to calculate, even with these fitbity, harmony, you know, activity trackers. selling you how many calories you've burnt, you know, they're notoriously inaccurate. That being said, okay, first of all, even if you don't lose a single ounce of weight when you exercise, exercise is fabulous for you. You have to do as much of it as possible, even if you don't lose any weight. But second of all, while it's not good for weight loss, it is actually

particularly good for helping you maintain your weight. So in other words, once you've lost your weight because you've reduced your food intake, and say you got to a weight that, you know, now I've X amounts of kilos. Being slightly more physically active helps you maintain that weight loss. How about this idea that you often hear of the fat burning zone? So if you're on your bike or you're running on an exercise bike or something, a certain heart rate percentage of your max, then you'll be operating in different zones. Is there any truth to that? You are burning as much fat as you possibly can all of the time. So that's, so, so that, that's the thing, because let's put it this way in terms of just putting some numbers down, the average human being,

depending on how much fat they carry, will, will contain anywhere contain, carry anywhere between 50 to 150,000 calories of fat, okay? Nine calories for every, nine calories for every gram of fat. Whereas, and probably around 2,500 calories in carbohydrates, glycogen and in glucose in the blood. Protein is not a store, it's all functional. So we are largely in terms of our energy store fat. And so we will burn as much fat as we can. The problem is that once we get to a higher intensity, we cannot convert fat into energy quick enough without the help of carbs.

So if we're doing low intensity training, such as not even training, if we're just living. So here, having this conversation with you, we are burning largely fat. But the moment we start to walk, we start to run, we start to climb a mountain, we start to do anything, then we start to burn carbohydrates because that's very, very easy to burn. But people don't know this, but actually, but together, if you actually put carbohydrates and fat burning together, it helps burn fat quicker. So there is some truth in saying that at a lower heart rate, you're burning more fat,

but we're burning fat all the time. And another like a personal anecdote, which I really liked because it's happened to me before, although not on quite as extreme level as it did you, was when you were cycling and you skipped the food stop and then just completely, you know, balked out. You crash. Not not crash, but you go, oh, and isn't it? And I look down and listen, I've got a bit of a wobbly belly and I'm going, do so does the energy. Use it. Use the energy. But that's not how about, it's about, I spoke to someone, an expert about this. And at the end of the day, it's the energy there, but fat, because it's very densely packed together, this is why it's our long-term energy stores. Our body just takes a little bit more time to extract the energy from fat. It will happen, but in the meantime, we're feeling ravenous.

You know, sadly, even though we're still got a lot of fat on us. So just sort of by way of closing this calorie section off then, so what's the maximum benefit? I can get. What's the most sensible, scientific way I can approach calories and calorie food labelling? That's a very good question. I don't know if I have the correct answer. I feel that in this book, I am bringing up a problem. So my goal, and we need to understand the problem before we can solve the problem, my goal in writing this book was not to change the nutritional labeling system per se. But what I realized, as I was writing and thinking about this, is that, when we look at foods that are lower in caloric availability,

meaning our body has to work harder, they have a couple of different characteristics. They're always going to be higher in protein and or fiber, depending on the type of food we're actually looking at. And so if we actually look at the quality of our food that we're eating, the diet, okay, and if we are eating something that has slightly more protein and a lot more fiber, we're actually, in shorthand,

talking about a pretty good proxy for healthy food, right, or healthier food at that any rate. And so I think this caloric availability concept allows you to take pre-packaged food, you can recalculate, you know, using 70% of protein, et cetera, et cetera, and actually understand the quality of the food because you're looking at the protein and the fiber. And I think that's the most important thing. I'd like us to, we worship the calorie as a society. I'd like us to think less about the calories, but more about the quality of the food that we're actually eating,

which we do need to improve. So that brings me nicely on to just to close that off then and just say that I really liked the phrase that you had. If you focus on health, your weights will take care of itself. Yes, I mean, people think that that's not true. I want to look like Brad Pitt. I do want to look like Brad Pitt, but that's not what I'm talking about.

I'm talking about the fact that people equate health and beauty, which is not necessarily true, all right? This is the thing. Whereas how much weight does Mrs. Smith need to lose in order to become metabolically more healthy, a lot less weight than she imagines. How much weight does she need to lose, to look like Angelina Jolie?

That's a very different number. So I think we need to think more about our health rather than necessary beauty and the weight in of itself. It's easier said than done, but there we go. Thank you for listening to this episode of Instant Genius. That was Dr. Jars Yo. If you'd like to know more about the science of nutrition,

check out his book, or to hear him tell me more, head over to the Instant Genius Extra podcast. The summer issue of BBC Science Focus magazine is out now. Pick up a copy in store or visit sciencefocus.com. This podcast is sponsored by Name, Audio and Focal. The texture and emotional depth of music can be lost through digital sources or poor signal. Name Audio believes you can have digital precision with analog warmth. Alongside French acoustic specialist.

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