How about you don't stuff your fat fucking face with absurd quantities of processed garbage steeped in refined sugar, fat and God only knows what other additives and then, while you're not doing that, try to burn at least as many calories as you consume. It really is that simple.
If you are fat it's because you are greedy and lazy, you have to choose to be fat and then embark upon a years long odyssey of self abuse in order to achieve fatness, other people just eat sensible amounts of healthy food and go for a walk from time to time.
