Is there a keto metabolic advantage? Can you grossly overeat on a low carb diet without gaining fat? Some say you can. I disagree.
Can you eat as many calories as you want on a low carb diet without gaining weight? Is there some kind of a keto metabolic advantage that allows you to eat more calories compared to a high-carb diet without gaining extra weight?
Can you grossly overeat on a low carb diet without gaining fat?
There seems to be a growing trend in online low carb communities to claim that calories don’t matter, and you can eat as much as you like, even grossly overeat, as long as the extra calories come mainly from fat, and as long as you keep your carbs very low.
The idea is that the only way to gain fat is through an insulin response. So insulin, as the fat storage hormone, needs to be elevated in order for fat storage to happen. Carbs of course raise insulin, and protein does too (though to a lesser extent than carbs). But fat has no effect on insulin production.
So the theory goes like this: as long as your carbs are low and your protein is low to moderate, you can add as much fat as you want without gaining weight.
The overeating experiment
Sam Feltham conducted a fascinating experiment on himself. He ate 5000 daily calories of a low carb, high fat diet for 21 days. He did not gain any fat, or at least not as much as the CICO (Calories In, Calories Out) theory would have expected him to gain.
When he repeated the experiment with a high-carb diet, he showed a significant weight gain.
This is of course anecdotal evidence, but it’s still very interesting, and shows that at least for some people, the response to a caloric surplus is NOT fat gain, as long as the diet is low in carbs and the extra calories come mostly from fat.
My own experience
However, I don’t think that this is true for all of us. I’ve been eating a low carb diet for five years now. I’ve had plenty of time to experiment. My personal experience is that when I overeat for prolonged periods of time – one or two weeks – I do gain visible fat even on a low carb diet.
Unlike Sam Feltham, I am a woman. I am also older than Sam – I am in my mid forties. So this could make a difference. It’s possible that women react differently to extra dietary calories and fat.
In addition, when I eat extra, it’s always low carb, but it’s not necessarily low protein – on a normal day I eat around 120 grams of protein, and on a high-calorie day it can be as high as 200 grams. I never consciously tried to limit my protein and make sure the added calories are only in the form of dietary fat, because I don’t think I would enjoy eating so much fat, and it’s important to me to enjoy my food.
So one could argue that my high protein consumption on high-calorie days triggers enough insulin release for fat storage to happen.
In terms of human evolution, does it really make sense to assume that the human body is unable to store fat on a low carb, high fat diet? My assumption is that up until the agricultural revolution, the human diet was low in carbs, and people relied on meat and fish, only using plants as supplements to their meat-heavy diet.
If a low-carb, high fat diet is the diet we consumed throughout human evolution, it just doesn’t make sense to me that we were unable to store fat on such a diet, because then we would have become extinct. Obviously, humans were able to store fat when they feasted, then survive on the fat stores in times of scarcity.
Of course, those animal flesh feasts likely provided plenty of protein, so again, maybe that’s what caused an insulin spike and fat storage.
Even if it’s true, do you really want to eat this way?
Assuming that it’s true – that you can avoid gaining fat when you eat a surplus of calories, but that the only way to do that is to keep carbs very low and protein low to moderate, the big question is – why would you want to eat like that? So you keep carbs low, but then you can’t even have a big juicy steak – you need to have a small steak and drown it in butter – where’s the fun in that?
Eating extremely high fat and strictly limiting protein is, in my opinion, unnatural. For me personally, and I’m not alone in this, too much fat gives me nausea and heartburn, so it’s simply impossible for me to eat 5000 calories per day of a very high fat diet.
So whether there is a keto metabolic advantage or not, I think I am going to stick with my delicious 2,000-or-so daily calories of steaks, burgers and well-buttered vegetables. 🙂