Exercise seems to prevent non insulin dependent diabetes. It can also help insulin resistant children of diabetic parents, who usually have a 40 per cent risk of developing diabetes themselves.
Although the reason is not clear, researchers have noticed that exercise increases insulin sensitivity, caused by a two fold increase in insulin stimulated glycogen synthesis in muscles. Glycogen is the carbohydrate made from glucose, released into the system as the body needs energy
!AN Engl J Med, 1996; 335: 1357-62.