I have a couple more points to make about obesity.

First, we know that if we eat less and exercise more we will lose weight. So it seems like you can blame people for making bad choices or not trying hard enough.

But we also know that we can consciously stop breathing. But few people have the willpower to hold their breath until they pass out. I used to spearfish, and every spear fisherman worth his salt has passed out underwater at least once (you don't drown, your throat latches shut, you splay out with an arched back, and your buddy pushes you to the surface where you wake up and ask "did I get the fish?"... and only idiots spearfish without a buddy). With practice, you can indeed hold your breath to the point of passing out, but it is difficult and takes practice.

Keeping the weight off is also difficult, and over a much longer term period of time (your entire life, no matter what else is going on) it is difficult to maintain weight via willpower. In fact studies show that it is pretty much impossible to do it longterm with willpower.

The other thing I'd like to direct your attention to is not a thing, but a person. Mandy Sellars (look her up). Mandy has huge legs and a very skinny torso. She is eating far too much food for her 17 stone legs, but far too little food for her emaciated body from the waist up. Given the exact same diet, it is making part of her very fat, but another part of her very skinny. What if your whole body was made of her greedy leg tissue? Would it be your fault that you were fat and yet still hungry all the time?

Finally, as I mentioned in some replies, even if you are going to fail, it is worth trying to lose weight. Small weight loss, repeated yoyoing, it is all better than nothing. We all lose in the end anyways.