I disagree, when people are losing weight quickly they almost invariably are eating far fewer calories. There’s some technical exceptions (such as that different nutrients are absorbed at different efficiencies, etc.) but they’re not large enough to make a huge difference in practice.
A lot of people think low carb or other weight loss diets work simply by preventing fat cells from uptaking glucose, in a low insulin environment. This is wrong, people losing weight on low carb diets are eating much less calories than they used to: if you were to force feed your old high calorie intake as fat instead if carbs, you wouldn’t lose weight. You can argue about the biochemical mechanism by which hunger is reduced but the reduced calorie intake is obvious and significant.
For the most part, calories printed on the back of a box are a good approximation of how much energy your body will actually absorb from them. It’s not something “entirely different.” Diets work mostly by reducing hunger, not by decreasing metabolic efficiency or energy absorption from food (see the link I added to my original post).
The obesity epidemic has been accompanied by a massive increase in calorie intake… however before the obesity epidemic people weren’t counting calories- they were just satisfied with less calories because their hunger was being regulated properly.
Then in as much as you yourself tried to make the claim a scientific tautology, a restatement of conservation of energy, you are plainly and trivially wrong.
Physics conserves energy as one of its fundamental properties. It so happens that humans are also good at conserving energy—and even reasonably good at treating our three main macronutrient sources as fungible—at least with respect to their use for energy production. That’s the rather impressive product of billions of years of evolution. But saying that humans are able to do this because “technically it applies to everything since it’s just a restatement of conservation of energy” is a ridiculous equivocation.
I never said or implied that humans can interchange nutrients from one form to another because of conservation of energy, there’s plenty of examples of chemical energy that the human body can’t do anything with. That isn’t related in any way to the point I am trying to make.
I don’t think I communicated clearly what I was trying to say, so I’ll restate it:
You are right that merely considering estimated calorie intake, and estimated calorie expenditure is a drastically over-simplified model of what’s going on that fails to account for many things.
However, it’s accurate enough to meaningfully model weight loss in humans. When someone switches to a paleo diet and is losing 2lb/week (as happened to me for a solid 6 months when I did), it’s not because they’re using lots of energy by some mechanism not accounted for in the over-simplified calories in/calories out model.
If you estimate food intake, you will find that a person losing 2lb/week on a paleo diet is in fact eating roughly 7000kcals a week less food than they used to.
The paleo diet doesn’t cause some metabolic condition under which the estimated calories in/calories out model is drastically inaccurate: it primarily causes overweight people to eat much less food.
I disagree, when people are losing weight quickly they almost invariably are eating far fewer calories. There’s some technical exceptions (such as that different nutrients are absorbed at different efficiencies, etc.) but they’re not large enough to make a huge difference in practice.
A lot of people think low carb or other weight loss diets work simply by preventing fat cells from uptaking glucose, in a low insulin environment. This is wrong, people losing weight on low carb diets are eating much less calories than they used to: if you were to force feed your old high calorie intake as fat instead if carbs, you wouldn’t lose weight. You can argue about the biochemical mechanism by which hunger is reduced but the reduced calorie intake is obvious and significant.
For the most part, calories printed on the back of a box are a good approximation of how much energy your body will actually absorb from them. It’s not something “entirely different.” Diets work mostly by reducing hunger, not by decreasing metabolic efficiency or energy absorption from food (see the link I added to my original post).
The obesity epidemic has been accompanied by a massive increase in calorie intake… however before the obesity epidemic people weren’t counting calories- they were just satisfied with less calories because their hunger was being regulated properly.
Then in as much as you yourself tried to make the claim a scientific tautology, a restatement of conservation of energy, you are plainly and trivially wrong.
Physics conserves energy as one of its fundamental properties. It so happens that humans are also good at conserving energy—and even reasonably good at treating our three main macronutrient sources as fungible—at least with respect to their use for energy production. That’s the rather impressive product of billions of years of evolution. But saying that humans are able to do this because “technically it applies to everything since it’s just a restatement of conservation of energy” is a ridiculous equivocation.
I never said or implied that humans can interchange nutrients from one form to another because of conservation of energy, there’s plenty of examples of chemical energy that the human body can’t do anything with. That isn’t related in any way to the point I am trying to make.
I don’t think I communicated clearly what I was trying to say, so I’ll restate it:
You are right that merely considering estimated calorie intake, and estimated calorie expenditure is a drastically over-simplified model of what’s going on that fails to account for many things.
However, it’s accurate enough to meaningfully model weight loss in humans. When someone switches to a paleo diet and is losing 2lb/week (as happened to me for a solid 6 months when I did), it’s not because they’re using lots of energy by some mechanism not accounted for in the over-simplified calories in/calories out model.
If you estimate food intake, you will find that a person losing 2lb/week on a paleo diet is in fact eating roughly 7000kcals a week less food than they used to.
The paleo diet doesn’t cause some metabolic condition under which the estimated calories in/calories out model is drastically inaccurate: it primarily causes overweight people to eat much less food.