When I weighed 118 lbs and was trying to gain weight, I would consume close to 10,000 calories a day. I would eat constantly, and not gain any weight. The only way I was able to gain weight was to cut back on my exercise regiment. I stopped bench pressing and exercising regularly, and only then was I able to gain some weight, but it's been nine years, and I haven't been able to put that weight back on. I lost 32 lbs in less than two months, but I can't gain 32 lbs in nine years. I am convinced that that has nothing to do with how I eat, or how active I am, because my father and my oldest brother are the same way. We have no problem dropping weight, but we can't gain weight.

My other older brother, however, is a big guy. He's tall, and he has a large frame, and he also has more body fat. I believe that that is also genetic. He doesn't over-eat, he does yoga every day, and he texts me every time he poops, so I know his metabolism is about the same as mine is right now. Him and I have the same dietary and exercise regiment, and we have a similar metabolism, yet he has more body fat than I do. This is why I believe that body type is purely genetic.