Obesity was long considered a personal failing. Science shows it's not.
Faced with reams of scientific evidence, the medical community has begun to stop blaming patients for not losing excess pounds.
www.yahoo.com
Seeing a lot of articles like this in addition to it being pushed in the media when it comes to females at least.
As for the causes most are things that personal decisions can change even though it might not be easy for many.
My own belief is all these trash processed carbs and sugar are the biggest cause of the epidemic as they put the body in a fat storing state.
Other causes I think are too much candida (bad gut microbes at high levels), which lead to strong cravings for those trash processed carbs, and thyroids being out of whack due to nutricial deficiency of certain minerals.
As for that claim in the article that about a 1/4 of people don't have this issue it's probably because many of them have good self control. There certainly isn't 1/4 of the population that has that teenager metabolism many people have then where they can't gain weight.