I agree with X. It is people not exercising and eating junk day in day out. I got anorexic thin at one stage and have worked hard to gain weight, but still a few kilos below my recommended weight. It's too hot to walk outside so I just walk around my home in circles building up the steps on my reader. It's not hard to study for an hour and stretch your legs for 10 minutes. The Apple guy tells his staff that sitting is cancer and I agree with that. Move, move, move. You can rest when you are dead and then the weight will fall off you even quicker.