I think obesity may be genetic. Like some people are tall and others are short, why can't how you store fat also be a genetic trait?
I mean I think genetically speaking, you will favor certain type of food better than other. If you favor candy and things of that nature, then it is more likely that you will become obese simply because of the high calories.
I mean look at families with large amount of brothers and sisters. You will see that in some cases, there is always one who is larger than the rest. Why is this so? Everyone probably eats the same food and probably gets the same amount of exercise.
Even more so, if you look at natives in those discovery channel, you will see that some are larger than others. Why is this? They eat the same food and they have to actually hunt for their food.
I think genetics will determine your overall body shape and whether or not your body favors to store fat more than usual. I think you can control things like eating excessive chocolate if you're genetically programmed to like those type of food. But I think any internal actions, such as fat storage and height and so fort cannot be altered.