The best comments I've seen about this is when you look at cumulative storage needed over time to gain weigh vs the total amount of energy consumed, the 'imbalance' is an accounting error.

Simple physics says one thing, simple engineering says another which is anything controlled that finely is under hormonally driven feedback control.

Frankly I think in the 20th century, particularly in the US and Britain there was a strong cultural imperative to assign psychological causes for conditions medical 'science' wasn't able to explain. So fat people are gluttons, erectile dysfunction is physiological, ulcers are caused by physiological stress. Heart disease is caused by a 'type A personality'.