Asked by: Anthony Dee, Dublin
It's to do with Newton's second law of motion, which can be written as acceleration = force/mass. The heavier you are, the more force an opponent has to exert to get you moving and push you out of the ring, or to lift and throw you. The heaviest wrestler ever weighed 267kg, which no weightlifter has ever lifted.
As much of the weight as possible needs to be muscle, rather than fat, to provide the necessary force. To achieve this, wrestlers eat massive quantities of high-protein chankonabe - a chicken, fish and tofu (and sometimes horse) stew.
A wrestler who could get most of this weight in his feet, and retain body strength, would be impossible to topple.