There's been a misunderstanding. I agree with you that direct caloric balance is unobservable on an individual basis, it can only be approximately estimated. I

There's been a misunderstanding. I agree with you that direct caloric balance is unobservable on an individual basis, it can only be approximately estimated. I'm saying that weight and appearance are observable, and that diet is adjustable. Want to gain weight? Change your diet a bit, observe the results over the following weeks. Repeat until satisfied. Want to lose weight? Change your diet a bit, observe the results over the follow weeks. Repeat until satisfied. Some people do these with old-fashioned calorie counting. Some with specialised diets. Some but dropping sweet drinks. But unless you first internalise the locus of control, you won't get anywhere.