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

Fat (although not the kind of fat you eat) is just the way the body stores excess energy. Because in nature food is scarce and/or unreliable, your body doesn’t want to not use energy you spent the time and effort to consume. So instead it converts those sugars into fat, which it can easily consume later.