Instant Genius - The truth about bodyfat

Episode Date: December 8, 2023

At this time of year most of us will likely be a little concerned about piling on a few pounds after overindulging in food and drink over the holidays. But what is happening in our bodies when gain a bit of extra insulation? Why is fat more likely to be stored in certain places, are all types of bodyfat the same, and are some people really more prone to gain weight than others? In this episode we catch up with Dr Rebecca Dumbell, a researcher based at Nottingham Trent University’s School of Science and Technology. She tells us all about the different properties of the fats we consume, how body fat comes in different forms and what we should be doing if we want to shift that troublesome spare tyre. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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Visit name audio.com to learn more. Hello and welcome to Instant Genius, a bite-sized masterclass in podcast form. Each week you'll hear world-leading scientists and experts talking about the most fascinating ideas in science and technology today. I'm Jason Goodyear, commissioning editor at BBC Science Focus magazine. At this time of year, most of us will likely be a little concerned about piling on a few pounds after overindulging in food and drink. But what's happening in our bodies when we gain a bit of extra insulation?

Why is fat more likely to be stored in certain places? Are all types of body fat the same? And are some people really more prone to gain weight than others? In this episode, we catch up with Dr Rebecca Dunbell, a researcher based at Nottingham Trent University's School of Science and Technology. She tells us all about the different properties of the fats we consume, how body fat comes in different forms, and what we should be doing if you want to shift that troublesome spare tire.

So today we're talking about fat. So I think the best place to start here then, what exactly is fat, you know, chemically speaking? And how does it differ from carbohydrates or protein? So I'm assuming you're talking about dietary fats, so the kind of fat that we eat and we ingest. And of course, there is fats that we store in our body as well. And obviously that's related. So fat, chemically speaking, is composed of glycerol molecule, which is a three-carbid. molecule and then three different fatty acids. Fatty acids are fats as well, but together these

are triglyceride and that's generally the kind of fat that you're going to eat. It's what the body will break down and then convert back into triglycerides and store in your fat cells or your adipocytes in your body and that's what body fat is is kind of made up of as well. So sort of moving on from that then, what role does fat actually play in our bodies? Yeah, so it's, first of all, it's really important for your health. You have to have some fat in your body to function and it has multiple different functions. So, you know, different kinds of fats are important for connective tissue, so different membranes that your cells are basically made from.

And adipose tissue itself, so where those triglystis, those lipids are stored is really important as a like a safe storage of energy. So taking glucose and other forms of energy that your body uses, storing them as fat for a time that it's then used later on. So for example, when you're asleep, you're not eating. So you don't have that kind of ready glucose in your body, which fuels all the different biological processes. and in that time you'll go into what we call a fat metabolism,

so a fat burning mode, and then those fatty acids that are broken down from those triglycerides are used to fuel all those bodily processes as well. There are other functions of adipose tissue. It's an endocrine organ. There are multiple different parts of your body where you store fat, these organs that release hormones, and they have lots of functions,

including influencing how hungry you feel as well. So you mentioned there the storage of fat. So how is fat stored in our bodies? So we have these fat depots or fat kind of organs in different parts of our bodies under the skin, maybe around your tummy, maybe, well, we also have deeper fat depots, we would call it a visceral fat depots as well. and they're made up of lots of little fat cells. And in those fat cells, there's one big, what we call a lipid droplet, which is a fat droplet.

And those fatty acids are taken up into those cells, glucose is taken up to those cells. And also building blocks from proteins can be taken up into those cells and then converted into lipid, usually as triglyceride. and stored there for later. And those cells can expand, like, get really big over time as well as they fill up. So you mentioned the expansion there. Is it possible to gain and lose fat cells? So fat cells live for a really long time. I think we know they live for at least about 10 years and probably longer.

So we know that if you gain weight and you're storing more fat in your body, more fat cells can be born and then they can fill up with lipid to kind of safely store all this energy that's not required at the time. As you lose weight, those lipids, those fatty acids are released and used as fuel, but those fat cells generally stay there,

which means that if you gain weight again, they can fill up a bit easier because you don't have to make more fat cells in that time or maybe you do make even more fat cells. But we don't think that we're generally losing those cells over time. So is fat more likely, you've sort of touched on this, but is it more likely to be stored in specific areas? So in different parts of the body, do you mean?

Exactly, yeah. Yeah, yes. So I kind of touched on this before. So we all kind of store fat under our skin, and we call this subcutaneous fat, and then we can also store it more kind of centrally and closer to our internal organs. Sometimes people call this the body cavity, but your body's not a cavity, is it? You're full of other things.

So you're quite close to your internal organs, and you would call that visceral fat. And people have different kind of body shapes depending on where they naturally store their fat. And that's generally inherited. It doesn't seem to be something that we can easily. influence and we know that it also has health consequences or rather it's associated with risks of developing health consequences as well. So we know that if people naturally store more fat around their tummy around their middle, someone's apple shaped, then they are more at risk of developing things like cardiovascular disease and type 2 diabetes, even if they have the same

amount of fat on their body as someone else who stores more of their fat around their hips and around their bottom, someone may be pear shaped, you might call them. And we don't really know exactly why that is, but we know that there's, well, lots of people have lots of ideas about that. So we know that subcutaneous fat is, which you get kind of around your hips and around your legs and your arms and your whole body just under the skin, is considered more like a safe storage of fat compared to the visceral fat. And we know that it is physiologically different as well.

So it could be that it develops from different precursor cells, like to turn into fat cells. We know that different genes are switched on in these subcutaneous fat tissues compared to in the visceral fat tissues. And we know that they're maybe more efficient at taking up triglycerides from the blood, whereas visceral fat is maybe a bit more ready to release those triglycerides fatty acids into the blood, which might then have poor health effects as well. So it could be that some people can make more subcutaneous fat cells. So they're taking all the fat into those kind of safer storage areas. And then less of that has to go into those visceral depots.

And it's actually that they have more fat cells in those other areas rather than if someone stores more fat around their tummy, maybe they just run out of space in their subcutaneous fat depots, essentially. Ambition comes in all shapes and sizes. At First Citizens Bank, we roll with your goals because we're built. for what you're building. Fit for your ambition for citizens back. It's peak pollination season,

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So sort of delving into the differences in body fat a little bit deeper. So there are actually several different types of fat cells, aren't there? So what's the difference between them? So when you probably think about fat tissue in the body, you're probably thinking of what I would call white adipose tissue. And this is what I described earlier. These are the cells with the big kind of space in the middle to store all those triglycerides.

And that's their job. Their job is to take in glucose, sometimes proteins and fats from the circulation and store that. And that can expand and contract. They produce lots of hormones and so on. We know that we also have brown adipose tissue. And this tissue is called brown adipose tissue because if you look at it, well, if you look at it under a microscope or whatever, it actually looks brown because it's so full of mitochondria. And if you know what mitochondria do, they burn a lot of energy. And in fact, the mitochondria in these brown adipose cells are able to kind of bypass that normal process and just create lots and lots of heat. So they're almost the opposite of white adipose cells because their job is to burn energy rather than to store energy. and we didn't really think that adult people had brown adipose tissue at all until really the early 2000s.

So we knew that babies have it and that kind of makes sense because they're very small. You think about the body size, the surface area is a lot bigger and also babies find it more difficult to put a jacket on if they get cold. So it's kind of helps them to maintain their body temperature. and it was kind of discovered by accident in people in a study where people were looking, I think it's like a cancer tracer and they basically inject them with this signal that you could pick up on a CT scanner that would be very dark in places where you're burning a lot of energy and so in a tumour you would pick up on things like that and you see it kind of highlights

the heart. It's obviously very energy consuming organ and the brain a bit as well. But they also found that it was lighting up across the kind of collar bones and down the spine and around the kidneys. And they didn't really know what that was. It turns out the waiting room was really cold. And these people actually had brown fat that was being activated by the cold. and it was burning lots and lots of energy, and that was lighting up in these images. And that's kind of how they found that by accident. So the other, the third type, is beige,

or it's sometimes called bright adipose tissue or adipocytes, really, because it tends to be that it's kind of small numbers of cells within subcutaneous white adipose tissue. and like the name suggests, it's kind of an intermediate kind of cell. And so they're a little bit bigger than brownidipocytes. They've got a few less mitochondria and a few more lipid droplets in there. And they do burn a lot of energy like brownidipocytes, but not quite as much. And yeah, so this is something that a lot of people are very interested in working on

because there's some idea that maybe, well, we don't really know where, well, there's conflicting ideas about where these cells come from. So there's some evidence that they are kind of a completely different cell type that are kind of born from different, you know, beginner cells.

Or they could be white adipocytes that have turned into these beige or bright adipocytes. So existing fat cells that kind of change their function. And the idea is, that if you can kind of influence that with a drug or some kind of treatment, you could switch people's existing fat storage into a more energy burning storage, which of course would help people to lose weight. So a lot of people have been kind of looking at that as well. So we've talked a lot about energy there. So let's have a look. One of fat's biggest sort of properties is for storing

energy. So what happens in our bodies when we break down fat to produce energy? Yeah, so fats can be broken down into their constituent parts, so glycerol and fatty acids. And just like your body can use carbohydrates as a main fuel source to kind of burn energy, fuel, all the different processes that it costs to be alive. You can also use fatty acids for that process as well. And that's what generally happens when you are, when you're fasting, when you're asleep and also doing some types of exercise as well. So let's have a look at perhaps diet a little bit now then. So say if I eat a very fatty diet, am I more likely to gain weight as fat? Or is it just simply a matter of the amount of calories that I'm consuming?

So I think in terms of, you know, what you're eating, fat is a really energy-dense food. So for, you know, for the same grams of fat or carbohydrates or protein, you get much, much more, I guess, for your money, you get much more calories per gram for fat. It costs, I mean, so if whatever you eat, carbohydrates, sugary foods, and protein rich foods. All of that can be converted and stored as fat. But of course, if you're eating fat, it doesn't cost energy to convert that into fat. So again, I guess that's going to be, you're going to get, it's going to be more easy to deposit that as fat rather than having to, you know, the energy it costs to do that.

Yes. Also, it's going to depend on what kind of fats that you eat. So you probably hear about saturated and unsaturated fats. And what that means is those fatty acids that are part of that triglyceride structure, they're all different depending on really the number of carbons, how long that carbon chain is. And on each carbon, there's obviously space for two hydrogen atoms as well. And so when it's saturated, all of those carbons have got two hydrogens attached to them.

And if it's unsaturated, that means that there's kind of gaps in that chain. And what that does is it changes the shape, I guess, of that fatty acid. It's able to kind of kink and so on. And that has an effect on, well, yeah, it's kind of a sort of a, associated with how good or bad for you in very simple terms, I guess, that is. So saturated fats are linked to risk of heart disease, stroke, high blood pressure, type 2 diabetes and so on, whereas the more unsaturated fats have a lower risk of developing these kinds of things.

So it's kind of a rule of thumb then, if I'm in the supermarket. What are some good fats I should be looking out for? and some fats that I want to avoid. Well, I think that dietitians usually would suggest going for the more, you know, polyunsaturated fats. And these are usually things that are, I guess, in very simple terms, more liquid. So, you know, if you have something very saturated, a block of lard, which is really just its animal fat or butter, I guess,

or even coconut oil, which is solid at room temperature, has quite, has a, apprising amount of saturated fat in it. But it's always important to have balance, I think. So I still like to eat butter on my toast, for example. Me too. Yeah. So sort of coming off the back of that, what about foods that are labeled as low fat? You know, what's going on there and are they actually any better for us? I think that in terms of if you're trying to reduce your fat intake, they're definitely useful but quite often when you take fat out of foods it's replaced with something else and that can often be sugar so and remember that if you're eating a lot of sugar that can also contribute to your body fat because that can that will eventually at some point be stored as fat

if you're consuming more calories than you're using yeah so let's sort of flip that the other way around then. So say I've got a few extra pounds that I want to shift. Is losing body fat simply a case of burning more calories than I'm consuming? I mean, in simple terms, yes, because that's physics. But the problem is it's not simple because we're all people. And if it was easy for everyone to just do that, there wouldn't be an obesity epidemic. So, which there is. So I think the thing with that is everyone is different and we know that a lot of that has to do with things like your underlying genetics and also the environment that you're in. And some people will find it easier to lose weight just naturally because of their innate physiology and the genes that they've inherited from

their parents than other people will. So yeah, it can be really challenging and obviously there are lots of people with lots and lots of advice on how to do that. But I think really, the thing is to find what works for you individually and try your best at that, really. So is it possible then, say I've got a bit of a spare tyre that I'd like to get rid of. Is it possible to lose body fat from specific areas? Can I target that? Unfortunately not. No. So I think, I mean, what you can do, guess is you can target exercises to tone certain areas. But again, where people store fat on their body is very much inherited. So there's lots and lots of big genetic studies have shown that really

a lot of that is to do with the kind of underlying genetics. And you can't change that. Your body shape is your body shape and you can lose weight and you can gain weight, but you can't control where from, unfortunately. That is a shame. So what about the sort of advice then? What's a healthy range for body fat percentage? You know, what are the guidelines there? Yeah, so it's different for men and women, and it depends on your age as well.

So for men, what would be considered a healthy body fat percentage, so the percent of your body weight, which is fat, is depending on your age, between 10 and 25 percent, And for women, it's about 10% more. So between 20 and 35%, depending on your age, usually. So you get a little bit more leeway as you get older. So say somebody's listening and they're interested in knowing what their body fat percentage is. Can they measure that at home? So there are ways to measure that, which are not too reliable, but it can be done at home. So you can buy, you know, weighing scale. that measure the impedance of your fat, and it will give you a read-out a percentage from that. The more accurate ways to do it are more difficult

because you need to go to a special facility. So it's essentially measuring the density of your whole body, and that's how we get that percentage body fat. And that can be done by something called underwater weighing, and again, it's measuring the displacement and the density. of your body and some facilities will have what's called a bod pod which looks like a really big egg and you get in it in your swimming costume with a swimming cap and it's very similar to the underwater weighing but it's measuring the displacement of the air and the most accurate way is using something

called dexar which is like a kind of x-ray type technology and again that's measuring the density of your body and it measures even your bone minimal density as well as your body fat percentage. But most people don't do that obviously so the way most people measure their own body weight

I mean it's body weight isn't it? So they measure their weight and they measure maybe waist circumference just with the tape measure or BMI as well BMI is a whole other conversation I know lots of people have lots of opinions on that because it doesn't take into account what your body is made of.

Maybe you're a bodybuilder and you have an obese BMI but obviously have very low body fat. So obviously these statistics on a big population level are really, really useful. But obviously you have to take into account individual people as well, you know, when you're thinking about yourself. And that's where, you know, being able to calculate body fat,

I guess, is more useful. So I think some people listening, there's maybe quite a few, will be worried that they're carrying perhaps a little too much body fat and they'd like to lose a little bit. So what would your top tips be for those people? This is my least favourite question, but it's the one that I always get asked. But yeah, I think coming back to what I said earlier, everyone is different and everyone finds it more or less challenging than their neighbor or whoever they're comparing themselves to. So the first thing I would say is be kind to yourself and to other people because body weight

is regulated by your body through the brain and through fat tissues and hormones and lots of different things. And everyone's kind of fighting their own physiology to lose weight. So I think the best advice is you've got to find what works for you because it's not going to be the same thing for everyone. Some people really like sugary drinks. Some people really like crisps. Some people really like jam on their toast or something like that. So, you know, I think being kind to yourself and really finding something that's going to work for you is probably the best way forward. Thank you for listening to this episode of Instant Genius. Brought to you from the team behind BBC Science Focus. That was Dr Rebecca Dunbell. The current issue of BBC Science Focus magazine is out now.

Pick up a copy wherever you buy your favourite magazines or download us on your preferred app store. You can also find us online at 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 vocal, Name creates high-end audio systems combining innovation with craftsmanship

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