Eli5 Why do mammals put on weight depending on how much activity they do and calories they consume

Question

Eli5 Why do mammals put on weight depending on how much activity they do and calories they consume

In: Biology

Answer 1

to be able to spend it, literally.

Your body doesn’t want to spend energy. The ideal scenario for your body is: you laying down, getting feed in the mouth by someone else and sleep all day (not saying that you want it, but that’s how your body behaves).

So, if you start using these calories, your body will try to find “a new normal” and require for you to at least eat the amount spent back in.