ZOE Science & Nutrition - The keto diet uncovered: The truth about fat vs. carbs

Episode Date: January 19, 2024

Each day this week, we’re examining one of the world’s most popular diets. Putting the latest scientific evidence under the microscope, we’ll find out these diets' true impact on your health. Today we’re talking about the keto diet, a global phenomenon favoring fats over carbs, lauded for potential health benefits like improved blood sugar control and weight loss. Yet, the allure of keto does come with downsides. With a dearth of fiber and essential nutrients — as well a reputation for being notoriously difficult to keep on top of long-term — many find ketosis elusive. In this special episode of ZOE Science & Nutrition, Jonathan is joined by Christopher Gardner, a professor of Medicine at Stanford University and the Director of Nutrition Studies at Stanford Prevention Research Center. Together, they unravel the keto diet's complexities, addressing its potential and pitfalls.  If you want to uncover the right foods for your body, head to joinzoe.com/podcast and get 10% off your personalized nutrition program. Top tips for better gut health from ZOE Science and Nutrition — Download our FREE gut guide Follow ZOE on Instagram Timecodes: 00:00 Introduction 00:42 Topic Intro 01:54 Why would anyone follow the keto diet? 02:59 What's the theory behind cutting carbs and switching to fat? 04:16 What happens in your body if you follow keto correctly? 05:59 What are the possible health benefits of switching to the keto diet? 06:34 What are the downsides to following the keto diet? 07:54 Keto diet study 10:01 What's the verdict? 11:37 Outro Have feedback or a topic you'd like us to cover? Let us know here Episode transcripts are available here.

Hello and welcome to Zoe Science and Nutrition and our special daily series about diets. Each day this week we're examining one of the world's most popular diets, putting the latest scientific evidence under the microscope. We'll find out these diets' true impact on your health. I'm your host Jonathan Wolfe and I'll be joined throughout this series by Professor Christopher Gardner. Hello Christopher. Good to be here Jonathan. Christopher is a professor of medicine at Stanford University

and the director of nutrition studies at the prestigious Stanford Prevention Research Center. He's one of the world's leading researchers on how our diet impacts our health. So what's on our plate today, Christopher? To kick us off, Jonathan, in episode one, we're dishing up a diet where fat reigns supreme. So fat reigning supreme sounds pretty scary when for decades, Christopher, we've all been told that fat is deadly and going to kill us and we all need to eat low fat. Now, I know the scientific view has changed and we no longer think that fat is deadly, but exactly how much fat are we talking about in this diet?

Well, we're talking about 70 to 75% of calories as fat when the argument has always been around the range of 30 to 35. So this is twice all of that. So that's an enormous amount of fat. What diet is this? So this is the ketogenic diet. Hi, I'm excited that you're here to find out if fat really is healthier than carbs.

If you haven't already, please hit follow in your podcast player so you'll know whenever a new episode arrives. This will really help us to continue our mission to improve the health of millions. So the team did some research and found that the ketogenic diet or keto, as I think many listeners will have heard of it, has actually been around since the 1920s. So it's a hundred years old, Christopher, and it started life as a treatment for children with epilepsy. So why would anyone with epilepsy follow this keto or very low carb diet? And why are we talking about it still a hundred years later for everybody? Yeah, it's fascinating. So if you do go back historically,

I think it was partly accident that they found out, let's try for these poor kids with epileptic seizures. How can we help them? Let's try different things. And this very high-fat, very low-carb diet suppressed seizures. It was effective. So it's been known for a long time. And what is the reason why people are now thinking that this could be a healthy diet for

people who aren't suffering from epilepsy? So it's gone around multiple times. A long, long time ago, it was called the Stillman diet. It was the Atkins diet. And the Atkins diet came and went and came back again. And lately it's surfaced as keto, which is a little almost extreme Atkins diet, but it has come and gone for years and years and years. And it seems to really be back bigger than I've ever seen it before. It's this backlash to low fat. This is super low carb. And what's the basic theory? Why are you cutting out all of these carbs and switching to fat? So your basic diet has carbs and fats and proteins for calories. And you can store an infinite amount of fat in your body. You can store a limited amount

of carbohydrate in your body, and you can't really store any protein. So as you're eating carbs, that generates an insulin response to put the carbohydrate away when blood glucose hits your cardiovascular system. And people with diabetes know they don't wanna have high blood glucose. So one of the possible ways to regulate that is to have less carbohydrate. Well, if you're gonna have less carbohydrate,

you have to have more of something, right? And so you could have more fat or more protein. So the basis of this idea is you cut out all these carbs, you don't create any sort of spikes in your blood sugar. So you don't have any of this insulin, any of those things that might be affecting, you know, diabetes, but you have to eat something else instead. Exactly. If you go back to the Atkins diet, interestingly, as you read through that, and that was very popular multiple times, there was no recommendation for the split between protein and fat. It was really just low carb. Keto is a little different. So what happens in your body if you do follow this ketogenic diet correctly?

So you shift from burning carbs to burning fat, which sounds great because then you're burning maybe excess weight and fat in your body, which you would like to get rid of, but it really is a shock to your body. Your brain, your central nervous system, they want glucose. If you deprive them of glucose, you can break down fat in a way that feeds your brain and your central nervous system, but it really prefers carbs. listener of this podcast, you're no doubt already aware of how important the gut microbiome is. It's responsible for so much, from digestion to immune support and even our mental well-being. As we've heard many times on this show, and as our members know through using Zoe,

we feed our gut microbiome through the variety of foods that we eat. And in return, our microbes give us this wealth of health benefits. So how can you nurture your gut in the best way? Which food swaps can you try to nourish those good bacteria? What does a high fiber shopping list look like? Our free gut health guide shares it all. Emails and actionable tips that are designed to put you in control of your gut health. To get yours for free, simply go to zoe.com slash gut guide. So I think the analogy that I'm sort of getting from this is a bit like you've got your car and it can be an electric car, but it can run on petrol as well. And what you're saying is it

really wants to run on petrol, but if you get rid of all the petrol, it'll switch to electric. But as soon as you give it like a bit of petrol, it sort of switches back to this because that's just its sort of default way. Is that an analogy that works at all here for my body? It does. And it really has to be super low carb to make that happen. So this is five or 10% carbohydrate when most diets around the planet are 50% carbohydrate or more. So it's like 10 times less carbohydrate than the normal ways that people eat around the world. So it's an incredible restriction of carbohydrate. And there's a blood level that you can check and it's called blood ketones. So if you are in ketosis, you can do a test and see if you have this. If you are at 15 or 20% carb, you are not in ketosis.

If you're in 10, maybe. If you have 5% carb, you're in ketosis. Most people can't do that. And so let's say you manage to do this. You're following the ketogenic diet. You know, you're very committed. What are the possible health benefits if you do switch to this point when you're sort of running on fats instead of on blood sugar?

Yeah. So you really wouldn't need any insulin to put away carbohydrate that's showing up in your blood. And insulin is a hormone that's very, the term for this is called anabolic. It's building. It's putting away. It's storing. Storing carbs as fat.

Storing fat as fat. Storing fat as fat. So you're shifting your hormone profile to be burning. That's the way it should work. And so what is the reality then? What actually might happen? And are there any downsides, I guess, if you do successfully follow this diet? So a lot of people get the keto flu from this. So in this big shift, they become nauseated. It's just, it's not good. And it cuts back on your appetite, which helps you lose weight, but it's not fun to be nauseated. There's also a misunderstanding. So a lot of people focus on the very, very low carb and not on the high fat part. And meat, in fact, is very low in carb, but it's high in protein. And so a misinterpretation people have is, oh, this is

great. I'm going to go super low carb. I'm going to eat a lot of meat. Our protein needs aren't really that high. If you start cutting that low in carb, it's really easy to exceed your protein needs. And since there's no place to store protein, it gets converted to carbohydrate, which is what you were trying to cut back on. So if you eat too much protein, actually, you can't be on a ketogenic diet. You aren't actually in ketosis. Yeah. And protein, extra protein is insulogenic, which means it produces insulin to be putting away the protein that turned into carb. This really is a very high fat diet in order to follow it.

Super high-fat. We did a study that we covered in a previous episode with you. I remember you're one of the very few people who've done a big study of the ketogenic diet. And I guess, what was the verdict out of that study, Christopher? Well, I have to tell you. So part of that study meant providing participants with food for four weeks from a food delivery service. And we said, hey, food delivery service, we are very much into having the best diet A and the best diet B. And I work with a lot of chefs these days. I love the term unapologetic deliciousness. We want you to make an unapologetically delicious set of keto meals for our participants. And this had to be a week at a time. And it came in jars. And one of the jars they gave us was all olive oil. And we said, well, we wanted meals. We need you to deliver meals. And they said, well, we can't get the fat high enough. And what should

you do with the jar of olive oil? And they said, pour it on your pulled pork, pour it over your avocados, pour it over everything. I thought, that doesn't sound right. We were trying to deliver meals, not jars of fat. And they said, having a really tough time getting the fat to the level you want. So one of the hardest challenges is just making this a sort of edible diet, is that?

It is. And in that particular study, when we fed people the food from a food delivery service, some of them did well, some of them just couldn't do it. Then they were supposed to do it on their own without a food delivery service. A couple of people actually nailed it, but a lot of people had trouble. We measured them 12 weeks after the study was over. Virtually no one was on it at that point. They couldn't maintain that low level. And I think what that means is some of them might have felt they were doing the ketogenic diet, but you're saying because it's so extreme in terms of what you have to achieve, they weren't getting that level of carbohydrate low enough,

and therefore they weren't actually switching to this fat burning. So they weren't really getting the theoretical benefits. And an amazing part was, so we were measuring blood ketones during the study and a lot of them that were actually doing okay, they were five or 10% carb, they still weren't in ketosis. So it's really hard to get there and stay there. So Christopher, having studied this yourself a lot in detail and having looked at the results of your own studies, what's the conclusion about the keto diet? What's your verdict?

So my verdict is total thumbs down. I work with preventive cardiologists and they have patients coming in all the time with very high LDL cholesterol. When you're eating that much fat, and remember, there's saturated, monounsaturated, and polyunsaturated, the nutrition community is pretty much all against saturated fat, which is in meat. So these people are eating a lot of meat, getting a lot of saturated fat, and their LDL cholesterol goes very high. And preventive cardiologists are very worried. Final question. Is there any exception, for example, people who have quite advanced type 2 diabetes, or are there any particular cases where

you would have a different view on the ketogenic diet? Not really, especially after our study, because I think the main issue here is added sugar and refined grain. In the U.S., that's 40% of our calories. So if you were to cut back on that, but maintain whole grains and nuts and vegetables and fruits, you'd be maybe at a 40% carb diet or a 35% carb diet. You would no way be in ketosis. But if you got rid of all the crappy carbs, that would be fine. So for keto, I'm all for getting rid of crappy carbs, but not going beyond the veggies and the fruits and the whole grains and the beans. Christopher, I think it's pretty clear that's about as comprehensive a thumbs down for a diet as you're ever going to get from a professor.

Thank you very much. And tomorrow on to the next diet. I can't wait. Thank you, Christopher, for unraveling the keto craze for us in today's conversation. Part of our special series of daily episodes about diets and our health. I'm Jonathan Wolfe. And I'm Christopher Gardner. Join us tomorrow when the pendulum of diets will swing to the opposite end of the spectrum and we'll be discussing low-fat diets. As always, the Zoe Science and Nutrition podcast is not medical advice. It's for general informational purposes only. See you next time.