It's pretty easy to come up with ways the body wouldn't take up calories. I and everyone here has had diarrhea for example. I've eaten 5k calories on a sedentar

It's pretty easy to come up with ways the body wouldn't take up calories. I and everyone here has had diarrhea for example. I've eaten 5k calories on a sedentary day with no impact on weight as well tho it's hard to account for water without a strict accounting. What's harder to refute is the loss of weight due to calorie restriction which is mostly physics. This is what the gp is talking about.