The problem is, half of them don't even know they have it. The earlier you can catch diabetes, the better chance you have of controlling the disease, and preventing long-term complications. People with type 2 diabetes have a resistance to insulin.
Exercise can help change that by moving their glucose into their muscles.
It improves those glucose transporters. The best advice for a person who has diabetes and is planning to start an exercise program is first, go see their physician to make sure they don't have any undiagnosed complications. And if they do, get those treated before they're put on an exercise program.