Feel Better, Live More with Dr Rangan Chatterjee - BITESIZE | The Bitter Truth About Sugar | Professor Robert Lustig #552

Episode Date: May 1, 2025

Today’s guest is a leading public health expert who has long been exposing the myths of modern medicine and the food industry. Feel Better Live More Bitesize is my weekly podcast for your mind, body, and heart. Each week I’ll be featuring inspirational stories and practical tips from some of my former guests. Today’s clip is from episode 251 of the podcast with medical doctor and Professor Emeritus of Paediatrics, Dr Robert Lustig. Dr Lustig’s passion is in communicating how excess sugar and ultra-processed foods are fuelling the chronic disease epidemic that we are all facing today. And, in this clip, he explains why eating too much sugar can be so damaging for our health and shares some practical strategies that we can all use to help. Dr Robert Lustig will be a guest speaker at Prescribing Lifestyle Medicine Live: The Evolution of Metabolic Health – from gut to brain and beyond, held at County Hall in London on Saturday 10th May. If you are a Healthcare practitioner, join me, Dr Emily Leeming, Dr Ayan Panja, Dr Robert Lustig and others. Book your ticket using code DRC50 and save £50 on the ticket price. https://www.tickettailor.com/events/practiceunbound/1535137 Show notes and the full podcast are available at https://drchatterjee.com/251

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For example, it contains calcium which contributes to the normal function of digestive enzymes and biotin to maintain your own intestinal mucus membrane. Subscribe now and get a free bottle of Vitamin D and five free AG1 travel packs with your first subscription. See all details at www.drinkag1.com forward slash live more. Welcome to Feel Better, Live More Byte Size, your weekly dose of positivity and optimism to get you ready for the weekend. Today's clip is from episode 251 of the podcast with medical doctor and leading public health expert Professor Robert Lustig.

Professor Lustig's passion is in communicating how excess sugar and ultra-processed foods are fueling the chronic disease epidemic that we are all facing today. And in this clip, he explains why eating too much sugar can be so damaging for our health and shares some practical strategies that we can all use to help. What are the key negatives when we consume too much sugar, or I guess the levels of sugar that many of us are currently consuming? Well, first of all, let's make it very clear that sugar is not the only problem in our diet. It's the big one. It's the 2,000 pound gorilla in our diet, but's the big one. It's the 2000 pound gorilla in our diet,

but there's other stuff too. But sugar is a particularly egregious molecule. Once upon a time, trans fats were the worst thing we consumed. Trans fats are the devil incarnate. Trans fats, the bacteria can't chew it up, which is why they put the trans fats in, all right, so that, you know, it would last forever. You know, the 10 year old Twinkie.

Well, the fact is our mitochondria, our little energy burning factories inside all our cells are really refurbished bacteria. We can't chew it up either. So the exact same reason for why they put the trans fats in the food is exactly why you shouldn't eat the food. Now we know that and they've come out of our diet. So now sugar is public enemy number one.

So what does sugar do? And the answer is a whole bunch of bad things. The food industry says sugar is energy. Well, they're correct. If you're a bomb calorimeter, if you just blow it up, if you explode it, yeah, you get four calories per gram. But we are not bomb calorimeters. Turns out that sugar actually poisons the mitochondria. Okay, it poisons it at three separate enzymes that are necessary for mitochondria to do their job.

The first one, AMP kinase, which is the fuel gauge on the liver cell. The second one, ACAD-L acyl-CoA dehydrogenase long chain, which is necessary to get fatty acids into the mitochondria to be able to oxidize them to create energy. And the third one is CPT-1, carnitine palmitoyl transferase-1, which is the enzyme that regenerates carnitine,

which is the shuttle mechanism that brings the fatty acids into the mitochondria in the first place. In other words, when you consume sugar, you are poisoning your mitochondria. You are generating less of the chemical energy that our cells get powered by called ATP. So if you're making less ATP, is that energy? It's the opposite of energy. It's the opposite of energy. So when you consume sugar, you are actually inhibiting your body's energy production.

Can you think of a chemical that inhibits your mitochondria and reduces ATP production? Cyanide. Cyanide does that. Sugar and cyanide do the same thing. Now, obviously, not as severely. Cyanide parts per million keel over and die on the spot with sugar. It's in the parts per thousand, and you don't keel over on the spot, but you feel lousy, and over time, it's going to take its toll. But ultimately, if

you're inhibiting your mitochondria, you are poisoning your body. And we now have the data to show how that occurs. Sugar is in virtually all ultra processed foods. and ultra processed foods are now 56% of the UK diet and the amount of sugar that Brits eat, 62% of it is found in the ultra processed food category. In 1977, the McGovern Commission released its report saying that we all needed to eat less fat to try to prevent cardiovascular disease. Well, when you take the fat out of food, it tastes like cardboard. And so what did the food industry do?

It basically replaced the fat with sugar. That's why we ended up with Entenmann's fat-free cakes and the like. And that was when the pasta craze first hit was, first hit was, you know, could refine carbohydrate because it was low in fat, et cetera. And, you know, now we're off to the races. And it's just exploded ever since. And Dr. Kevin Hall at the NIH did a study where he showed that when you give people ultra processed food, they burn less and gain more weight when everything else is controlled for compared to the same diet in real food. Did this in 2019. And you and I are both interested in mitigating chronic disease. And you are right. If you get people on a real food diet, you can mitigate virtually any and all of their chronic diseases.

I completely agree. You give a TEDx talk basically saying you can basically take away somebody's chronic disease. I used to do that in my clinic when I was practicing routinely, but only if they changed the food. And if they didn't change the food, no amount of medicine I threw at them could make a difference. Yeah. I mean, what strikes me as a really key message is that the majority of what we

are buying to feed ourselves and our families is ultra processed food, whether it's here in the UK or with you in America. And that is contributing to this tsunami of chronic ill health that we're seeing. It's pretty, you know, it's pretty alarming. But what I think is so key, Rob, for me is that it's so normalized now. Like it's the norm everywhere, schools, hospitals. In fact, if you want to go down the real food route, you almost feel like a bit of a, like, if you try and do it with your kids, you actually become a social outcast in some ways. And I think this is the problem. It's just, it's the norm.

We've moved so far away from what we used to do. Like you, I'm very passionate in root causes and this idea that we've labeled all these so-called separate diseases. We get talked about them at medical school as either one separate entities and then for this disease, you take this drug and you have this sort of treatment. And we look at that downstream pathology, don't we? But you mentioned mitochondria at the start in terms of what sugar or excess sugar can do to mitochondria. And that mitochondrial dysfunction sits at the heart of so many different conditions, but also insulin resistance, right? So is it the sugar that's inherently bad in

and of itself, or is it the excess amounts? I mean, or is it both, right? Because I think a lot of people might say, well, look, you know what? This never used to be a problem. We would have the odd sweet treat now and again. There's quite a few prominent scientists, as you're well aware, Rob, who say actually sugar's not a problem. Sugar's actually completely fine. We're working on it.

I have a bone to pick with some of those scientists and we can argue that and talk about that if you like as to exactly why they say what they say. So here's what I can tell you. There are social drinkers and there are alcoholics. Now, social drinkers can pick up a beer and put it down, and they don't need one every day. Alcoholics pick up a whiskey and can't put it down, and they need it three times a day. Right? Yeah. Did the one beer that the social drinker drink hurt them.

Unlikely. Unlikely, unlikely. And the reason it's unlikely is because there is a, what is known as a first pass effect. You drink the alcohol in the beer. First of all, it's very low percentage, right? It's only about 3.6%. And that is about, oh about 60 calories worth or so of alcohol.

And what happens is that the first pass effect, the stomach and intestine metabolize that alcohol before any of it ever gets to the liver. And so the amount that actually hits the liver that could do damage is exceedingly small. And as long as you're not following up with a second beer and a third beer and a fourth beer and a fifth beer, you know, like can happen at the Newcastle pub, you know, you don't usually have a big problem. Right. But if you keep doing that, then that is a problem. So it's a dose dependent phenomenon, and your intestine is there to try to protect your

liver from getting the onslaught before it will do damage. Same with sugar. No difference. So your intestine can take a small amount of sugar that you consume and can actually turn it into fat in the intestine, intestinal de novo lipogenesis, the process of converting sugar to fat into VLDL in the intestine so that it will not go straight to your liver. And about 10% of an initial sugar bolus will undergo intestinal DNL and therefore be diverted

away from the liver and into the bloodstream as VLDL. Now, that VLDL is not great for you because it could ultimately cause heart disease, but it's protecting the liver. But if you consume past your intestine's capacity to do that, now the rest of it's going to end up in your liver. And the problem with sugar in the liver is exactly the same as the problem of alcohol in the liver, because it causes the exact same processes. It causes glycation, it causes oxidative stress, it causes mitochondrial dysfunction, and basically

drives insulin resistance. This phenomenon that we now know is at the base of virtually all chronic metabolic diseases. Therefore, your pancreas has to make extra insulin to make the liver do its job, because now the liver is not working right because it's been poisoned. And so insulin levels rise all over the body. And now you've got the risk for Alzheimer's, you've got the risk for heart disease, you've got the risk for cancer, you've got the risk for Alzheimer's, you've got the risk for heart disease, you've got the risk for cancer, you've got the risk for virtually every other chronic metabolic disease on the plate, all because of what happened to your liver. And fructose, that sweet molecule in sugar, basically has the same fate as alcohol. So when people say, Oh, you know, little sugar is fine.

Yeah, because your intestine diverts that little bit away from the liver. As soon as you overwhelm that capacity. Now your liver is right in the crosshairs. And that's when chronic disease is going to start. Yeah. The term real foods. I like it, you use it. You know, my view, Bob, is that I found it to be very useful with my patients. Of course, if my patients don't like it, I'd come up with something else that they understand. But generally speaking, I think the things like, you know, would your grandparents recognize it as food? I think people find it quite helpful. Or does the food packet have more than five ingredients on it or not?

As a kind of general rough rule, they're not perfect, but they're all kind of guidelines to try and help people make sense of this ultra-processed food environment in which they're living. I find a lot of people, particularly in medicine and academia, look down on these kind of, what are considered simplistic terms. Yeah. I've heard those complaints also before. Basically, what we're saying, real food is food

that came out of the ground or animals that ate the food that came out of the ground. That's real food. Okay. As soon as a human touched it, now it's processed. Just a question of the degree of processing also. And, you know, I'm sure you're familiar with Carlos Montero at University of Sao Paulo,

developed this system called the Nova system for the degree of processing, which I actually think is the right way to go. It's not what's in the food, it's what's been done to the food that matters. All food is inherently good. It's what we do to the food that's not. That classification system is brilliant. Perhaps you could take a readily available simple food and just explain how it can go through these four stages to help people really understand this.

Sure. I can do this in one minute. Let's take an apple. Class one on the Nova system would be an apple. Class two on the Nova system would be apple slices. Class three on the Nova system would be apple slices. Class three on the Nova system would be apple sauce unsweetened. Class four on the Nova system would be an apple pie. There you go. Turns out that only the class four foods are associated with chronic disease. So we can have, you know, minimally processed foods that are done to make our life easier a little bit or, but it's when it goes to that extreme where it's actually bears no

resemblance to actually what actually came out of the ground in the first place. That's right. And so what is different about that apple pie versus the apple? And the answer is the addition of sugar and the removal of fiber. So the addition of sugar is what basically floods the liver, because the liver, like alcohol, only has an innate capacity to metabolize a small amount. We know how much sugar we can metabolize. It's not that different from the amount of alcohol that we can metabolize.

Because the metabolism is virtually the same. Point is, you can overwhelm your liver's capacity to metabolize sugar. When that happens, just like what happens when you over metabol can overwhelm your liver's capacity to metabolize sugar. And when that happens, just like what happens when you over metabolize alcohol, is your liver can handle the onslaught. And so it has to take the extra and turn it into fat. There are enzymes in your liver that turn sugar into fat.

It's called de novo lipogenesis, new fat making. And there are three enzymes in concert that do this. One's called ATP citrate lyase, the other one's called acetyl-CoA carboxylase, and the last one's called fatty acid synthase. These three enzymes are being driven by excess substrate. And that substrate is fructose, then turned into acetyl-CoA by glycolysis. Bottom line, you're flooding your liver, and the goal is protect the liver. When you flood your

liver, now your liver makes fat, and that fat precipitates. Now you got fatty liver, and now you got insulin resistance, and now you got insulin resistance, and now you got chronic metabolic disease. So protect the liver. Second part, feed the gut. Everyone now knows that the microbiome talks to your brain, which is true, it does. So feed the gut.

That's what a prebiotic does. So what's a prebiotic? A prebiotic is food for those bacteria that will feed them so that they can grow. And what's nature's perfect prebiotic? Fiber. Fiber. Fiber is not food for you. Fiber is food for your bacteria. But when we took the fiber out of the food to process it, because fiber basically reduces shelf life, when we

took the fiber out of the food to process it, we are now depriving our bacteria of the food they need to be able to live in symbiosis with us. And so those bacteria, the good bacteria are dead, the bad bacteria have taken over, and the bad bacteria sending all sorts of bad signals, actually suppressing serotonin generation in the intestine, thereby reducing the antiretroviral transport of serotonin back up into the nucleus tractus solitarius, and that's called depression. Also, because you're not feeding those bacteria, the bacteria are basically stripping the mucin layer right off your intestinal epithelial cells, because they can eat that. And that's then exposing and denuding your intestine and making it, you know, all the

junk that's in your intestine basically can get through called leaky gut, contributing to inflammation, inflammatory bowel disease, irritable bowel syndrome, and insulin resistance. All because you didn't feed your gut. And that's how the whole thing gets tied together here. That's some very simple, but very, very brilliant advice. Protect the liver, feed the gut. But the modern food environments, the ultra-processing of food is overwhelming the liver with sugar and it's starving the gut through its lack of fiber.

And then the consequences are the liver could be, you know, fatty liver, type 2 diabetes, but the problem when the gut gets starved and as you say, leaky gut or increased intestinal permeability sets in, then you're opening up for everything, autoimmune disease, food allergies, Alzheimer's, depression, all these things have been associated with increased permeability in the gut. So it's a very simple maxim, but one that actually, again, going to that nexus of the root cause, it's kind of right there, isn't it? This is the other thing I really liked, Rob, is that you don't seem to have a preferred diet. It's very much

like me. I'm always like you. It's unprocessed the diet first. Let's just get out the chunk. Let's get the real food in and then let's see where we are. So how does you feel that like a vegan diet or a low carb diet or a whole manner of diets can fit this maxim of protecting the liver and feeding the guts? Yeah, I'm agnostic as to the whole vegan keto thing. People who want to be vegan, you know, fine, whatever. You want to be vegan? Great.

Don't make anybody else feel bad about their choice. But you know, you can feel good about your choice. That's fine. Okay. their choice, but you can feel good about your choice. That's fine. There are a lot of reasons to be vegan, you know, animal welfare, religion, cost, coolness, if you will, but metabolic health is not one of them. Okay, and I can prove it

because Coke, Doritos, and Oreos are all vegan. So you can do vegan right or you can do vegan wrong. Keto. Okay. I'm not against keto. You know, bottom line is I don't have a preferred diet. I don't. I'm agnostic on it. I think there are a lot of ways to skin this cat.

I think ultimately we will learn the genetics of who does better with which diet and it will turn out that certain diets are better for certain people and other diets are better for other people. And I'm very interested and involved in this personalized nutrition concept and movement that's going on right now. and movement that's going on right now. So I'm for both diets. The only diet I'm not for is the Western diet. And the reality is, I think any clinician who has utilized food as one of their tools and their toolbox with their patients, which I hope more and more are starting to do, although it's clearly not enough, you will see that different people thrive on different diets.

I think real life clinical practice teaches you that, well, these guys here are literally rocking a low carb real food diet. Their markers look good, their bloods look great. And all these people here are doing great on a whole food vegan diet. As you say, the commonality is no processed food or very, very low amounts of ultra processed foods. The commonality is low sugar, high fiber. The diets work when they're low sugar, high fiber. And so that's why I think those are the two sort of linchpins in this whole story. Hope you enjoyed that bite-sized clip.

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