What does science tell us about the carnivore diet? | Stephan Guyenet and Peter Attia

I wanted to talk about the carnivore diet with you a little bit because I know you guys did a review on a book. Um, it's not a diet I've spent any time really thinking about. So I've basically spoken to, I don't know, a dozen people who have gone on it and without exception, they all lose weight. Um, which I think for some of them is their motivation for doing it. Um, and it must simply be that they just get tired of eating, right? They just don't, they just can't take in the number of calories. If they're doing it in that format. I think there's probably, so I would say that, you know, we don't have any good data on, um, the impact of carnivore diet on, on weight. So, you know, there's no randomized controlled trials, but you know, we have these anecdotes of people saying they lose a lot of weight. I certainly don't dispute that. Um, but I think if you came to me with this diet on paper and you asked me, would this cause weight? I would say absolutely because it has multiple properties that I would expect to make it a particularly effective weight loss diet. One, this is something we could talk about more if you want, but it has zero carbohydrate. So I think that anywhere, if you're on the extreme of the fat to carbohydrate, uh, ratio in either direction, that's more slimming than being in the middle. So the most fattening diets are rich in both carbohydrate and fat. So there's zero carbohydrate. You're on the extreme, or I shouldn't say zero, very, very little. The glycogen in the meat. There's a little glycogen. So you're on the very extreme end of, uh, the macronutrient distribution. It's high in protein. That's also known to contribute to weight loss. You're eliminating almost every type of food. So your variety, the variety of your diet goes very low. I mean, you can prepare your meat in different ways. You can eat chicken or fish or beef or whatever, but the variety is greatly, greatly reduced. So that's, I think part of it. Um, and you're cutting out all of these highly processed calorie dense foods that are the foods that I think, you know, we could debate about why, but I think everyone agrees that those are foods that drive excess intake and elevated body fatness. So I think all these things together, it's just even on paper, it's a diet that I would very much expect to cause weight loss more to greater degree than your average diet. And while we're on the topic, um, what are, I mean, tell me a little bit about your review of this, because I know you've put some time into this, uh, and for folks that are wondering, you know, I don't really plan to do a, do a podcast on the carnivore diet. I, um, I doesn't seem to make a lot of sense to me, although I don't dispute that there are people who I think have had very, um, successful outcomes on it with respect to dealing with some of their physical ailments. Um, so maybe it has a role in sort of overcoming some acute illness. Um, and maybe I'm just biased towards thinking plants are valuable, but I guess it seems to me that one of the core tenants of the, of the diet is that plants are sort of low, low grade toxic. Right. I mean, isn't that sort of part of the thesis? Yeah. The thesis is basically everything is toxic except grass fed animal foods. Um, so like even tap water is considered, uh, not optimal, but, um, yeah. So the book spends a lot of time like going through the litany of all the potentially harmful compounds in, in plant foods. And actually, you know what? I, I sympathize with some of this. I think there is a bias toward thinking if it's in a plant, it's healthy. And I don't think that's true. I think the book is right that that's not necessarily true. And I think there are some plant compounds that at least for some people are not so good. And you know, there are well characterized examples of this. Like if you eat a lot of spinach, you can get kidney stones from all the oxalate. Um, there are studies suggesting that the glucosinolates in, um, cabbage family plants might contribute to type two diabetes. Uh, you know, there's like kidney beans. If you don't cook them enough, they can be really toxic because the lectin. So it's not like there aren't examples of this. It's, it's definitely true that to some degree, I think it just gets taken far beyond where the evidence is. And you know, the way to think about how healthy a food is, is not to say, does it contain toxins? It's to say, what's the cost benefit analysis on this food. And most importantly, what are the empirical outcomes that we can see when it, when it's directly, when its impacts on health are directly studied. So, you know, like this is something that I've kind of focused on in my evaluation of, uh, some of the ideas that are put forth in the public sphere is that a lot of people with, um, a lot of people who are coming out with, uh, let's say unusual ideas in this sphere, they really, they take a mechanism and they run with it. Like, you know, X toxin is really bad. Like lectins, for example, Gundry, lectins can do X, Y, Z lectins are in plants. Therefore we shouldn't need these types of plants. And that's really like a bottom up approach, like extrapolating empirical effects on health from mechanism when really, I think in a complex field like nutrition, it's better to start with the empirical evidence like, Oh, we have this study that suggests that there's actually an effect on health. Let's see if we can understand the mechanism. What are some of the, um, biochemical changes that occur in people on a carnivore diet? I mean, the obvious one must be the dyslipidemia, right? Yes. So, you know, there is, there's a shift, uh, toward a ketogenic metabolism because of the fact that it's very low carbohydrate. Um, that would be an obvious shift that occurs. Um, there, you know, I, I don't know if I'd use the term dyslipidemia, but one of the terms that one of the potential downsides I focused on in the review that is, um, downplayed by many carnivore diet advocates, including Paul Saldino is, um, the change in LDL cholesterol and LDL particle count. So, and again, we don't have great evidence here, and this is kind of the crux of our review of the book on Red Pen Reviews is simply that there are a lot of claims made that are not supported by any kind of, uh, convincing evidence. But, um, we have some evidence. So there's this survey study that was done on something like 2000 carnivore dieters. Um, I think David Ludwig was involved in that. And they just reached out to people in social media groups, like their Facebook groups and things, and they administered this survey. And one of the questions was what was your various blood lipid values before and after this diet. And you see that there are changes in positive and negative directions. Triglycerides go down as, as you would expect. Um, I don't remember what HDL did, but it probably went up. Yeah. And then there was a large increase in LDL cholesterol. And so that's a concern, you know, as far as I'm concerned. And I think you would agree. And Paul Saldino himself, you know, I'm not trying to pick on him. I don't want to make it personal, but he's, uh, you know, been public about some of this stuff. So I think it's, it's fair to point out to just repeat what he himself has said, but his LDL cholesterol is 533 megs per deciliter and his LDL particle count is also absolutely through the roof. And, um, so not everyone responds like that. Like if you look at the survey data, I think there was a mean increase of like 30 megs per deciliter and LDL 30 or 40, something like that. Um, so I think it depends on the individual. I think some people like Sean Baker's lipids are fine. He's another carnivore diet guy. Last time I saw his lipids looked just fine. So I think it depends on the individual. Um, but some people do experience a large increase in LDL cholesterol. And I mean, you know more about this than I do, but that certainly raises red flags for me in terms of cardiovascular risk over the long run. Yeah. The thing I've never understood is, um, and this is probably true of not just carnivore, but ketogenic or anything that, um, that does produce that hyper beta lipoproteinemia. Um, uh, it's, it, it almost seems to be worn by some as a badge of honor, as opposed to saying, well, maybe this diet is doing a lot of really good things for me. It's improving my insulin sensitivity. I feel better. I have fewer energy swings, but this one thing isn't so good, but here's the thing of all the things that could go wrong. That's about the most treatable one out there. It's very easy to treat elevated ApoB. Uh, and so that's the part, I mean, and this is what we do clinically, right? This is how we treat patients, right? We have patients who only get better on very, very carbohydrate restricted diets, but then, you know, if they develop that, that pattern, that elevated LDL pattern, we have a choice to make, which is we abandon the diet or we treat the elevated ApoB. Um, and that's not a failure. That's simply using modern medicine to help us achieve the best of both worlds. So, um, I think I've always struggled to understand why a person will go on that diet, have, you know, an ApoB or LDL go from the 50th percentile to North of the 99th percentile. And instead of being curious about what the implication is, sort of dig their heels in and say, clearly, this is a good thing and LDL does not cause heart disease. I absolutely agree. I mean, it's, it's a dietary ideology. It's an ideology that has emerged to, uh, defend a certain type of dietary pattern. This, these kinds of ideas emerged from the low carb community, essentially to defend against the idea that there might be some downside to certain types of low carb diets. And they've been taken to an extreme, I think in the carnivore community, because that's a particularly, uh, potent stimulus for increasing LDL. So people don't want to believe that there's a downside to the thing they're doing. And, you know, like I kind of get it. Like people go on this diet, they lose weight, they feel better. Some people, you know, they say their skin cleared up or X, Y, Z condition improved. Like there's all these tangible things they can see that are getting better. They don't want to believe that there's an intangible thing. That's actually putting them at severe risk. Cause I mean, as you know, like I say severe risk, I just mean cardiovascular disease is a big risk generally. Like, as you know, this is the number one killer. Cardiovascular disease is a huge, big deal. Even if it doesn't kill you, it can do really bad things to you physically and cognitively. So like, it's not a risk you want to be ignoring. So I absolutely agree. I think it's an irrational part of dietary tribal ideology that is holding people back from experiencing their best health. And it's so treatable. I said that in the review too. I was like, you don't even have to stop the diet. You can just get it treated or you could modify the diet. Yeah. And, and, and by the way, it's the same, you see the same sort of equally stubborn ideology at the exact opposite end of the spectrum where you use, you know, we see these patients that'll go on these incredibly restrictive plant-based diets. And it's usually some combination of micronutrient deficiency and or protein deficiency that's going to be the death of them. But there's no deviating from it. There's no like, I'm going to supplement with protein shakes. I'm going to take B vitamins. I'm going to do these. And again, it's the same sort of thing. It's like, somehow if I acknowledge the fact that I need to supplement with these other things to work around a diet that I otherwise like, or that is congruent with a belief system I have around the treatment of animals, which I can respect that, right. If that's, if that's your belief system, then by all means be true to it. But but yes, I find it somewhat self-destructive. Yeah, absolutely. I think it's very analogous to what we see in certain corners of the vegan diet community. They want it to be best for everything. It's got to be best for the environment and for ethics and for health. And like, it's just very hard to swallow that there might be some downsides. And for the carnivore diet too, you see like they try to justify the environmental aspects of it too. Like in the carnivore code, he talks a lot about regenerative agriculture which, you know, is, is a concept that I think is interesting and I think I support it, but it's a certain, I would say spin on it that makes it seem particularly favorable. And also like there's an underlying assumption that the average carnivore is going to eat nothing but regenerative agriculture beef. Which I think is not the case.