This is widely believed but not true or supported by scientific evidence. Have a look at Gary Taubes "Good Calories, Bad Calories" for a rundown on much of the relevant research.

It's thermodynamics. Living takes energy, and that energy needs to come from somewhere. We can't photosynthesize energy, and we can't get it from air or water. So if there's not enough energy in food to sustain our body's processes, then it must come from stores in the body (fat).

I don't think there's any other possibility.

Weight loss only reduces to simple thermodynamics if the body is functionally equivalent to a coal furnace. It turns out metabolism is more subtle than that.

There are subtleties to nutrition and weight loss, of course. But let's say you stopped eating, and you didn't just die: do you think it's somehow possible to NOT lose body mass?

Of course not, and nobody here thinks that.

I didn't read the book but I wonder if what the scientific evidence concludes isn't necessarily the refutation of that equation, but rather that it's more complicated than x-y=z. For example, foods that require a bit more energy to consume such as foods high in fiber.

I mean, calories are just a unit of measure for energy, so if you consume energy, it must go somewhere, either expended or stored in the body. What happens if the body lacks the energy for its processes...doesn't it then burn fat? If you turn fat into energy, that means less mass in the form of fat, with the excess energy dissipating into heat. Isn't this just physics?

Yeah, Taubes' main point (simplified) is that your muscle and organ cells are pretty good at burning fat, unless you eat lots of carbohydrates, which releases insulin, which will tell your body to stow away any fat that's in your bloodstream instead of burning it. So while consumed - burned = loss is still true, eating a diet that is high on carbs will reduce the amount of calories you burn from the same caloric intake.

Carbohydrates also have the added problem of making your blood sugar swing, which leads to hunger pangs and bigger appetites.

Paradoxically, it's not fat that makes you fat, it's hormones and pasta/rice/potatoes/bread/sugar because they mess with those hormones.

If your body wants more energy, it will find a way to get it, either by inducing you to overeat, or by making you less active. So fixing your hormone balance (specifically insulin levels) is more effective than trying to control your food intake.

Of course, the fact that many restaurants and diners in the US serve really big portions, that most of us don't do a lot of exercise, that we have very easy access to high-calorie foods, that the food industry precision-engineers foodstuffs to be addictive... all of that surely doesn't help, but if Taubes is correct those environmental factors are not the chief cause of obesity.

It's not that they're good at burning fat, it's that they require more energy to operate. They will get that energy from anywhere they can, be it from diet, stored energy in the form of fat cells, or protein in the form of muscles.

Don't anthropomorphize the constituant parts of the anthropos.

Also, if your body wants more energy, it's for a reason, and that reason is that the processes of maintaining life require it. And yes, it will get it, but not by making you less active - that's the tail wagging the dog. You're less active in that case because your body can't support the activity rate without burning more calories.

I think the best way I managed to wrap my head around the refutation of that is this: First off, some foods make you hungrier so you consume more calories. People have a very strong tendency to eat when they're hungry. The might be able to put that aside for a short while (dieting) but its' very hard to combat in the long run

Secondly, it has to do with how the body stores fat. Eating fast carbs produces insulin which signals the body to store fat in larger amounts than low/slow carb.

It's a pity that the caloric model is so entrenced when really it's the least useful one.

Really, it's not rocket science,stop eating white foods, don't drink calories, eat quality meat and veggies,and your set.