Childhood obesity is the reason why even kids and teens are so much affected by diabetes.
It was common knowledge once, that being a little overweight adds life years! It's not a paradox, it's just not true.
Actually normal weight helps you to prevent cardiovascular disease and the trouble that comes with it. Not to mention diseases like cancer.
However, I prefer personally to think less about those serious diseases, because anyway obesity becomes a real problem: it would not let me even walk normally!