Gary Krieger says, " If dietary fat is more likely to be stored as fat than dietary carbs,
why is it that it's easier to lose weight on a keto diet than a higher carb diet assuming
isocaloric?"
Okay.
First of all, it was definitely true.
It's easier to store dietary fat as fat than it is to store dietary carbs.
Why is it easier to lose weight on the keto diet than a higher carb diet assuming isocaloric?
Well, I think there's an assumption that's not necessarily true there, but the ease with
which you store something as fat is not really related to weight loss.
So I think that's part of why that is true, or part of why there seems to be a conflict
there.
So the implication of the fact that it is easier to store dietary fat as fat than it
is to store carbs as fat is that when you eat too many calories from carbs, you will
have a lot more fat that is stored as fat because the carbs displaced their use for
energy.
In other words, the carbs were burned for energy instead of being converted to fat.
So the fat you put into your adipose tissue, if it was not easier to store fat as fat than
to store carbs, is that then you would expect to have under all conditions, sort of a general
mix of if you eat more carbs, let's say you had your excess calories were 80% carbs, 20%
fat, you would expect that your adipose tissue would reflect 80% fat that has been synthesized
from carbohydrate 20% fat that has been taken from dietary fat.
And it doesn't work like that at all.
If you eat excess calories, 80% carbs, 20% fat, the effect of the carbohydrate will mainly
be to be used for energy in place of fat that would've been used for energy and instead
is stored as dietary fat.
That's what it means for it to be easier to store fat as fat than to convert carbohydrate
to fat.
That has nothing to do with whether you lose weight, because whether you lose weight has
nothing to do with which molecule you stored as fat and has everything to do with the overall
caloric balance.
Now, assuming it's easier to lose weight on a keto diet than a higher carb diet, assuming
isocaloric by isocaloric, I assume we mean not relative to your caloric balance, but
they're the same calories in a high carb diet versus the keto diet.
Probably it's not.
So, that's generally been shown through self-reported dietary intake in free living populations.
And self-reported diet is not accurate and free-living populations do not report accurately
what they do.
Most people, unless they're tracking everything, do not even have a reasonably accurate sense
of what they're eating.
And so when you do metabolic ward studies, you generally don't see that advantage.
I do think that there might be a very small advantage that is due to the inefficiency
of gluconeogenesis, and that is due to the loss of urinary ketones.
So on an extremely low-carb diet, there probably is some metabolic inefficiency that causes
a slight caloric deficit, but that probably only applies at the extremes.
And it's probably very small.
And then it's not really isocaloric.
I think the overwhelming factor here is what's happening to your appetite and what is happening
to the sustainability of your caloric deficit.
And so I think there's a subsection of people that have really good appetite control kicking
in on Keto that allows them to eat less food.
And I think that because of that, it winds up being a more sustainable diet than some
other diet that would also introduce a caloric deficit that didn't improve their appetite
balance.
And they may say that they're eating isocaloric in a study, but if it's not done in the metabolic
ward and it's not highly regulated, the assumption should be that it's not isocaloric.
So, yeah, I think those are two completely separate things.
The fact that it's easier to store fat than convert carbs to fat is why carbs in the diet
displace fat in the burning of energy.
And that's not related to weight loss.
On the other hand, the reason some people do better on keto than on a higher carb diet
for weight loss, and I do not believe that's everyone, is because the keto diet is mainly
helping with appetite regulation and sustainability, and maybe on extremes, there's a very small
contribution from the metabolic inefficiency of gluconeogenesis and the loss of urinary
ketones, but that's probably less common and also very small.
All right, Gary, thank you for your question.
I hope that helps.