People who have huge muscles usually have high levels of insulin because insulin causes muscles to grow. Exercise makes muscles so sensitive to insulin that it prevents blood sugar levels from rising too high. However, when these people stop exercising, their muscles are not as sensitive to insulin and blood sugar levels rise, this causes insulin levels to go even higher, so they eat more and gain weight.
A study from Mt. Sinai Medical Center shows that National Football League linemen are more than twice as likely as other Americans to develop diabetes in later life. More than 60 percent of NFL linemen become diabetic, compared to only 30 percent for the average American (The American Journal of Cardiology, May 2008).
People who have large muscles when they are young need to continue to exercise for the rest of their lives. If they reduce the amount of exercise or stop exercising for any reason, they must do everything in their power to protect themselves from gaining weight. Before insulin can do its job of driving insulin into cells, it must first attach to special insulin receptors on the surface of cells. Extra fat in the body prevents these receptors from responding to insulin, so blood sugar levels rise even higher. To compensate for this, insulin levels rise higher also, which sets the person up for diabetes and premature death.