Instant Genius - Weight loss: What actually works?

Episode Date: July 27, 2023

 If you’re looking to lose a bit of weight, it’s easy to get lost in the complex and often contradictory health advice you can find online, from the fad diets, to the extreme exercise regimes.  But what actually works? To answer this and much more, we’re joined by Dr Adam Collins, Associate Professor of Nutrition at the University of Surrey. He unpacks the science-backed core principles of weight loss, why losing muscle alongside fat can be an issue, and what actually happens in your body during a calorie deficit.  Learn more about your ad choices. Visit podcastchoices.com/adchoices

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Music just as the artist intended. Visit name audio.com to learn more. Oh, and welcome to Instant Genius, the bite-sized master class in podcast form. I'm Thomas Ling, digital editor at BBC Science Focus magazine. If you're looking to lose a bit of weight, it's easy to get lost in the dense and often contradicting health advice you can find online, from the complex fad diets to the extreme exercise regimes. But what will actually work?

To answer this and much more, I'm joined by Dr Adam Collins, Associate Professor of Nutrition at the University of Surrey. He impacts the science bat core principles of weight loss, while losing muscle alongside fat can be a problem, and what actually happens in your body during a calorie deficit. Hello, Adam, welcome to the show. Good to be here. Fantastic. Okay, so there's a lot of advice out there

about weight loss. So much of it seems quite conflicting. So I should start by confirming one key basic. Is a calorie deficit eating less calories than the body uses? Is that a good strategy to lose weight? Well, I think the simple answer is that that's the only strategy for losing weight, because to lose weight, you'd need to have some form of calorie deficit. So when somebody has a calorie deficit, what happens in their body? So what happens in the first few days. So if you're in deficit, by its very nature, that deficit means that you've got a shortfall that you have to have to be met by the body. So in order to meet those calories that are missing, you have to use the calories that you've got stored in the body. And you have two main stores

of calories. You have carbohydrate stores and you have fat stores. And your carbohydrate stores are really your short-term buffer, which keeps you sort of rolling with the the punches on a day-to-day basis, and that's going to last you maybe one to two days worth. And that's because carbohydrate is not very energy-dense, so you don't get many calories per gram, and more so the fact that you have to store that carbohydrate with water, because chemically that carbohydrate joins with water when you store it. So it's very bulky, takes up a lot of space. that's one of the reasons why when you lose weight in the first few days,

that a lot of that weight is water loss because you're going to be sacrificing your glycogen stores. And that is often why you get a fairly big weight loss initially, particularly if you've got a significant calorie deficit, that that leads to a short-term dropping weight because of this loss of your weight. gycogen, your, your carbohydrate stores. It's okay if you can just unpack water weight a little bit more. So why is it that your carbohydrates need to be stored with water? And where in the body is this stored as well?

So just because carbohydrate is chemically like an organic molecule that joins, binds with water, so the bonds around it will bind with water. So it's a hydris store. So it associates with water. And that store is found in the liver and the muscle. So most of our glycogen overall is in the muscle, but actually the concentration or the biggest store per unit of tissue is it is actually in the liver. It's just that we've got a lot more muscle compared to the liver,

which is adding up to more of your glycogen stores. So that's where that store of carbohydrate comes from it. And obviously it takes up space. And that space is mainly due to the water. So if you think of glycogen might be four parts water to one part carbohydrate. So in terms of calories per gram, you might only get one calorie per gram. a thousand calories per kilogram as opposed to what you'd expect if it was just pure carbohydrate which would be close to that four calories per per kilogram.

So that's why you end up losing a lot of water weight because, of course, you've lost bulk in the form of water, which isn't any calories as you are releasing those glycogen stores. So you were saying that these sort of carbohydrate stores were last through between sort of one and two days. What happens when that sort of runs out? So can somebody really sort of feel it? Are they likely to feel a drop in energy? They're likely to feel quite thirsty if they lose a lot of water weight? Sort of, but what tends to happen is that you don't do things in a stepwise manner. So it's not like you use up all your glycogen stores. Then we'll know all those are gone.

You start switching to something else. You're transitioning all the time between what you can use and sacrifice in the short term and then you're trying to preserve that or shift as much as you possibly can to something more long term as a solution and that's where you start to use body fat as a store actually that starts to be sacrificed

and used within 12 hours of you being in the calorie deficit so that's already starting to switch allegiances to fat where you can but of course you have to use carbohydrate. You can't just use pure fat. You have to use some carbohydrate in the body, which is why you end up having to sacrifice some of your glycogen stores.

But at the same time, what you're also doing is not just preserving or switch into something else to conserve those carbohydrate stores where you can, but you're actually going to start to manufacture carbohydrate from scratch in order to sort of keep things going, you know, particularly keep a, because the whole point is to keep a steady supply of carbohydrate to your vital organs, particularly like your brain, which needs a constant supply. That's why your blood glucose, your blood sugar, is maintained within a fairly tight physiological range.

So just so we've got that right, so is it actually maybe after 12 hours on a calorie deficit where your body can actually start breaking down those fat stores while also using the carbohydrate stores as well. Yeah, but like I said, it's not a stepwise thing. You're just changing priorities or you're adjusting metabolic preferences in order to meet that calorie deficit. And that's why you're shifting from away from your sort of short-term solution to more of your long-term solution.

And the same goes in reverse. You know, same when you gain weight. You might gain weight relatively rapidly. To start with it, then eventually you'll shift to gaining weight in body fat terms, which means that actually you can sequester a weight quite a lot of calories without putting on much weight overall. So it goes in both directions, really. This podcast is sponsored by Name, Audio and Focal. With over 100 years of combined expertise, Name and Focal,

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Try it for yourself at a focal powered by name boutique. Visit focal powered by name.com for more information. I thought it's really interesting what you're saying about there's different tissues and organs in the body which can't use fat for energies, is that right? That's right. So the brain is one key one. because you can't get fat or fatty acids in particular that you release from your fat stores across the blood-brain barrier. So you have to use something else instead.

So obviously carbohydrate or glucose is the main supplier. But you can indirectly use fat in the brain by turning those fatty acids into ketones, which are able to cross that blood-brain barrier. essentially you're turning your fat into nail polish remover to get it across the which is essentially the same sort of chemical that you're using in the brain to get to get across that barrier what about like muscle tissues like can they use fat for energy or is that something separate yeah so so your muscle will start to use fat for energy to sort of spare the the need to use carbohydrate um so any carbohydrate stores you have have in the muscle, they're not going to be used for anything other than the muscle themselves.

But you might be depleting those muscle glycogen stores, but by the time you're starting to deplete those muscle glycogen stores, provided that you've got the means to, you will be using fat taking up and using fatty acids or fat instead of carbohydrate. So again, you're just shifting priorities, you're shifting to using your near infinite stores of calories in the form of body fat. I mean, you're never going to run out body fat, but you can easily run out of glycogen. And so that's why you shift to using that body fat as much as possible. So if you're on a calorie deficit, can that actually mean that your muscles start to break down a bit? Yeah. So in order to keep everything going and keep the supply lines constant,

you are going to sacrifice body protein in order to turn that protein into sugar. So your liver is starting to manufacture new glucose, new sugar from other things. And one of the things that it's designed to use is protein, because actually you can't turn fat into sugar. You can turn sugar into fat, but you can't turn it the other way around. So you're already starting, when you're in this what we call a catabolic state, which is basically you're in a deficit, then you're starting to release your stores, not just of fat and of glycogen, but you're actually shifting balance towards more protein breakdown. And that protein breakdown is starting to release amino acids, which can be used by your liver to manufacture sugar and keep that constant. flow of glucose to your vital organs.

And what consequence does this happen? Does it just mean that you lose muscle mass? Does it have an influence on someone's metabolism? It has both effects. So one of the effects is obviously muscle protein is one of the things that sacrifice because you're, yes, you've got some protein floating around the blood, some amino acids in the blood, but actually to keep that supply to this manufacturing of glucose, you have to. having to sacrifice some of your muscle protein. So you're shifting towards more what you call muscle protein breakdown rather than protein synthesis. So you're still going to have periods where you're probably doing protein synthesis, but overall you're probably in what we call net protein

breakdown or muscle protein breakdown during that catabolic state or that weight loss state. So what about the metabolism side of it? Does losing muscle mass? influence someone's metabolism? Yes, so there's a few things going on. So if we just think of muscle proteins, so your muscle, your skeletal muscle, the things that attach to your skeleton, are your metabolic consumers?

They're the things that are actually going to be using fuel and burning that fuel. I mean, yes, your organs are going to be consuming a lot, but actually in terms of the most variable component of you is going to be your muscle. So if you start compromising that muscle because you're breaking down that muscle protein and ultimately you might have less muscle overall,

or you've reduced that muscle mass slightly, then there's less of that metabolically active tissue. So in terms of calorie burning, you might end up burning less calories just sitting at rest because you've got less of you metabolizing you. So it sounds quite scary. if you say it slows down your metabolism. Does that basically just means the body uses less calories while at rest?

Yes, yeah. So when we think of something like your metabolic rate, which probably people have heard about before, your metabolic rate is really just a reflection of how many calories you burned lying at rest doing nothing. So that's like your minimal amount of energy that you need. So this is not you being active. It's not you eating and digesting.

So it's basically what we get you in the lab, meddle you after a 12-hour overnight fast, in a completely supine, rested state, how many calories are you going to burn? And obviously that is going to reduce if there's less of you to metabolize. So if there's less of you, then there's less calories that you're burning at rest.

But I think the thing with weight loss is, I mean, it's not just about the fact you're compromising, potentially body protein and losing muscle, which you might be doing. But your body is already increasing its methods of efficiency because, of course, it's in energy deficit. So anything that it can do in the same way as we're doing in the cost of living crisis, when you've got expenditure is higher than your income, then of course you need to try and reduce your expenditure as much as possible. And that's basically what your body is doing. So it's, trying to hunker down, become as efficient as it possibly can, on top of the fact that

there might be less of you that's metabolically active. That's not just muscle, but that's adipose tissue. That's your fat stores, because fat stores are actually metabolically active too. So even if you're starting to lose body fat, that has some metabolic activity. Not much, but if you lose a lot of it, it could make a difference. But all these things are added together. So that means that when you lose weight, not just the fact that there's less of you, because you've lost weight, that your metabolic rate goes down, but your metabolic rate goes down even more than that because your body is trying to increase its methods of efficiency. So it's becoming more and more efficient, burning less calories as possible in order to sort of minimize that deficit. It sounds almost quite cruel.

I guess if someone has the goal of fat loss, they turn to a calorie deficit. But then if you do this, you lose muscle, which makes slowing the metabolism even harder. Yeah, but I mean, let's sort of look at the positive. So yes, we might lose some muscle, and that composition of what you lose might be slightly different in the early phases. So we said about water loss. So maybe 50% of your weight might be lost as fat, and the other 50% would be lost as non-fat. a lot of that would be water, but some protein.

But even when you're in the throes of an energy deficit for some time, you're still going to be losing the majority of that weight is going to be fat. So the fat is going to be the main thing that you're going to be sacrificing. So you might be losing some body protein, but you're going to be losing a hell of a lot body fat on top of that. So maybe 75, 80% that weight is going to be lost. as fat and maybe 15, 20% or so is going to be lost as non-fat, which would be some water, would be as protein.

And that's not necessarily a bad thing because if you're carrying around less ballast, then actually you don't need as much muscle mass to carry it. So there's also efficiencies of movement that happen too when people are looking. weight. So some of that non-fat tissue is associated with the fat you're overweight to start with. So it's not always the fact that you're going to be sacrificing your muscle protein. When you're breaking down fat, your fat stores, it's not just purely fat that you're sacrificing. It's other things that are happening at the same time. All right. I thought it's really interesting what you're saying earlier about if

If a body loses fat to make it more efficient, it might also lose some muscle as well, which as you said might not necessarily be a bad thing. But if someone's goal was to just be losing more fat, is it a good idea to be maintaining muscle at the same time? Yeah. So what you want to try and do is minimize the amount of that muscle mass loss, particularly when you think of the function of that muscle. I think that's, you think that's probably more pertinent to look at it rather than just overall amount of muscle that you

have. It's how much of a service it gives you that muscle rather than just how much you've got. So you want to actually improve the, not just maintain the amount of that muscle protein, but it's contribution

to your metabolism or its metabolic function. So it's not just about having it, but being able to utilize it too. So, I mean, I think one of the issues that you get is that let's take someone who is overweight or obese, but is relatively sedentary or has low sort of muscle capacity. So they might have muscle mass. And they've got that maybe higher.

muscle mass than someone who's lean because they're obviously carrying around more weight, more ballast, but that muscle is not like they're a bodybuilder or they're an athlete and they've increased their muscle from that point of view. So the function of that muscle is different. And that's probably more important because what we know is that particularly when you get older, that that muscle will start to, in a way, deteriorate a little bit or the muscle function will start to sort of tail off, particularly when you get into your later ages, later years. And it's more important that you can try and preserve that as much as possible.

And of course, anything you do that could compromise it, it needs to be taken into account. So if you are going to lose weight, you've got that, particularly if you're an older individual, you need to be conscious of the fact that not only have I got to lose weight, perhaps for various health reasons,

because I'm carrying around too much body fat, which is the thing you're trying to lose, but I don't want to compromise my muscle function because that's going to put me in good stead as I get older, or I want to make sure that that is still functioning, as best as it possibly can as my main metabolic consumer, which I mentioned before. So across all ages, if you are trying to lose fat, is something like resistance training,

you know, hitting the weights? Is that quite important then? Well, yeah. So let's think about it from the point of view of a strategy. So I want to lose weight. So we've always said the strategy to lose weight is I need to go in a calorie deficit. However I do that, there's lots of means and ways of doing that. it, whether I do it consciously, unconsciously, whether I do it from diet and austerity or increased exercise or physical activity or combination of the two, or by changing food behaviour, food choice, these are all just means and ways of getting you to lose weight. And there's not really any evidence to suggest that one way is better than another,

or that there is really any major differences or metabolic advantages of doing it one way than another. The main thrust or the main mechanism of effect is the fact you're creating this calorie deficit. So let's say you've done that and I want to lose weight, but I want to make sure that I'm maximizing the fat loss and trying to preserve. as much as I can, the muscle mass that I've got. So I want to make sure, in a way, that I am trying to maintain what we call protein balance. So that I'm not in net protein breakdown. I might not be in protein synthesis, so it might be too much of a stretch to think I'm starting

to build muscle at the same time with me losing fat. But I want to make sure that I can preserve or maintain my protein synthesis. balance. So in order to do that, I need to do one or two things. I even need to stop or inhibit protein breakdown. So stop breaking down the protein or and or increase protein synthesis. And you can do both of those things. So obviously the energy deficit is going to be driving protein breakdown for reasons that we've seen. But perhaps that could be mitigated a little bit by another stimulus, which might be offsetting that a bit.

So that might be physical strain through the muscle, i.e. exercise, whether that's a resistance type exercise or just for making the muscle work will trigger some protein synthesis. or reduce protein breakdown to some extent because it's going to be triggering some more protein synthesis. But of course that on its own is not enough because you also need to be able to have the supply of the building blocks, basically, the protein

in order to allow for that protein synthesis to happen or in order to not break that protein down anymore. So that's why having that combination of exercise and protein feeding is probably the best combination because just feeding more protein on its own might not do the trick because you're still going to have that driver of that protein breakdown. And just doing exercise in its own might not be enough because that might stimulate protein synthesis, but you haven't got the building blocks in order to do that. So that's why when you look at weight loss interventions that have incorporated exercise, you need to ensure that you've also got adequate protein intake.

And those ones that have increased protein intake don't necessarily correspond to preservation of body protein if you haven't got another stimulus of physical activity or exercise at the same time. So what do you make other views of, say, scientists like Tim Spexer? that say the exercise doesn't necessarily directly lose fat. It's just all about supporting a calorie deficit that's mainly from not eating as much. Well, exercise's got a bad rap because, of course, people think that exercise

is something that doesn't create an energy deficit because you just compensate it by either eating more or being less active outside of doing that exercise, which to some people, extent happens and it's difficult to see the effect of exercise in creating an energy deficit in the same ways you would get with diet. So it doesn't seem to be as effective if your end goal is producing an energy deficit. But exercise is doing lots of other things. So it is obviously

contributing to energy demand. So of course it will be not just contributing to energy expenditure, but it will be driving consumption of fuel. So whatever that fuel is coming from the diet or coming from your body stores, it's going to be used more if you're doing more physical activity. So I think to say that exercise doesn't work is giving it a bit of a disservice. It's not as effective as a weight loss intervention on its own, but it will still contribute to an energy deficit. And we know that studies that have combined diet and exercise together are much more effective than just using diet on its own. But I mean, he's right in the sense that exercise dots lots of other things metabolically that help shift towards this more manageable

catabolic state and more importantly help adapt to sustain that new metabolic state so once you've lost that weight it seems to help people to be able to maintain that weight better and in terms of increasing somebody's metabolism by sort of growing muscle what do people need to eat to support that to support that muscle growth so obviously protein would be one thing and and if you think you're eating less calories overall, but then you're having to make sure you've got an adequate supply of protein, that at the very least should be trying to maintain the level of around 0.8 grams per kilogram per day. So if you think of your total diet replacements, like your very low calorie diets, your sort of shake and soup type diets, which are only going to

give you 800 calories a day, they obviously create lots of weight loss because it's a massive energy deficit. There's legislation to say that that total diet replacement has to have a certain amount of protein in it and it has to have a certain supply of your micronutrients. So it has to be nutritionally complete in terms of protein and micronutrients, which is why you have to do a total diet replacement because it would be very difficult to get that level of nutritional complete this just through food. So I'm going to put you on the spot a bit and I suspect this is not going to be an easy answer, but what is a good level of calorie deficit? How does someone know if they're cutting out a good amount of calories? Well, that's tricky, isn't it? So I will say

that one size does not fit all when it comes to energy deficit, but it's not so much about the energy deficit. It's knowing what effect that energy deficit is going to have. So if you've got someone who is say needing to lose say 20 kilos or 20% of their body weight because they're very overweight or most likely obese very obese getting them to say cut down 500 calories a day is not going to create I mean it's still going to be an energy deficit but it's not going to be a big enough energy deficit to give you a meaningful weight loss in a sustainable length of time. So that's why if you think of someone who needs to lose a lot of weight, then you need to think of more drastic ways.

Not drastic, that's probably the wrong word. You need to think of maybe tailoring a bigger energy deficit for them to achieve that weight loss. So maybe going on a very low calorie diet or bariatric surgery will be another way of getting them to significantly lose weight through a big energy deficit. Then you've got sort of another area where if you need to lose, say, 10 to 15% body weight loss, again, we know that unless you're in a very well-controlled, well-looked-after intervention trial, you get into literature, that generally people find it difficult to sustain that

level of energy deficit from your conventional 500 calories a day. So you can do it that way, but it needs quite a lot of support and it's difficult to sort of get that outcome. And that brings into play other strategies that you might use that might be looking at things like intermittent fasting or you might even think of the more modern advocacy of maybe using weight loss drugs that might have impact on appetite or changing behavior or even putting people on things like very low carbohydrate diets or changing the nature of that diet to not necessarily because putting people in a low carbohydrate diet's just going to miraculously getting to lose weight but because that shifts them into changing eating behavior to such an extent that and an easy

to follow sustainable way in which you can get that sort of weight loss. That was Dr Adam Collins, Associate Professor of Nutrition at the University of Surrey, talking through the science of weight loss. Thank you for listening to this episode of Instant Genius, brought to you by the team behind BBC Science Focus magazine, which you can find on sale now in supermarkets and newsagents as well as your preferred app store.

You can, of course, also find us online, at signfocus.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 Focal,

name creates high-end audio systems combining innovation with craftsmanship so you can listen to music, just as the artist intended. Discover more at Name, audio.com.