I do believe there is a genetics component to appetite/stomach capacity/hunger signals/etc. since I'm one of those people that has no problem downing 15-20,000 calories in a day. Hell, I've eaten enough before to go up 20lbs in scale weight in retained water/waste/salt/glycogen in 1 day. Of course I'm back down to my normal weight in the next 4-5 days from consuming a normal, healthy diet. The difference between me and an obeast though is that I don't eat like that everyday just because I have the capacity. I normally lead an active lifestyle and eat a diet consisting of mostly nutrient-dense whole foods. Genetics is absolutely no excuse to stuff your face everyday.