Imagine you had to carry around an extra 10 kilos with you everywhere. You'd get skinnier pretty quickly? So how come being fat is not self regulating? I have a theory that will require some weighing scales and a tape measure to test.
We get a canteen, and get a bunch of people who all get the same meal served to them. We then weigh the meal and the people, also get there height, gender and maybe age. Now if your fat you'd want to get less food served to you, if however you get more then a thin person your going to gain more weight then the thin person.
If it turns out that fat people get more food maybe we have a cause of fatness. You happen to get more food one day, gain a bit of weight, This makes the food disher-outer give you a tiny bit more food the next day. And your in a positive feedback loop.
We get the sex of the eater because I've noticed that women seem to get less food served to them then men, which considering they pay the same price is pretty miserable. If we can get a perchentage maybe we can get gender prices on meals. Also while I'm on the subject why do airlines allow a set amount of baggage? I weigh 85 kilos and am allowed 20 kilos=105 kilos. Someone who weights 60 kilos has the same baggage limit. Why not allow everyone 100 kilos including themselves and pay for the excess.