I don't know the exact reasons, but I know there's a very good reason behind why we gain fat in certain places. Because human beings were starving for most of our history, evolution has produced a body that's not only very efficient at storing fat, but storing it in specific places, and for good reason. I think a lot of it has to do with protecting certain organs. That's certainly the case for women, who have to be concerned about protecting their reproductive organs. That's why they tend to carry more fat in their hips, thighs and buttocks. It's also why women have a higher body fat percentage than men in general. I'm not sure what the reason is for men gaining fat in their midsection. Maybe ancient man really needed a place to rest his beer mug.

But even though it may seem like fat gets deposited everywhere, the truth is your body is a lot smarter than that. Just as you're smart (hopefully) about where you put your extra income, your body knows where best to deposit its energy surplus.