> What part of the laws of thermodynamics imply calories in -> calories out?
The part where you restrict your assessment to more or less normal digestive function? Obviously if your stomach explodes or your intestine just plain stop working, caloric intake/deficit is now one of the least of your worries.
I think you actually hit the nail on the head here though, in using the word "imply". Calories in - Calories out doesn't give you an exact picture, but it comes reasonably close for the purposes of most people.
It's by no means a perfect understanding, but someone who is obese needs simple rules that can successfully get them started more than they need a perfect knowledge of the science involved.
The part where you restrict your assessment to more or less normal digestive function? Obviously if your stomach explodes or your intestine just plain stop working, caloric intake/deficit is now one of the least of your worries.
I think you actually hit the nail on the head here though, in using the word "imply". Calories in - Calories out doesn't give you an exact picture, but it comes reasonably close for the purposes of most people.
It's by no means a perfect understanding, but someone who is obese needs simple rules that can successfully get them started more than they need a perfect knowledge of the science involved.