Losing weight is the single most effective way to prevent diabetes.

Reason: Putting on even as little as 10 pounds — especially around your middle — automatically increases insulin resistance. Losing just 15 pounds reduces your risk of developing diabetes by more than half.

A simple, proven way to lose weight: Eat smaller portions. Use small (10-inch) plates at home — and therefore serve smaller portions — since studies show that people tend to finish whatever is on their plates. Also, avoid fruit juices and soft drinks as well as “white” foods (white bread, baked potatoes and French fries, pasta, white rice), all of which cause sharp rises in blood sugar. Finally, make sure that every meal contains a mix of high-fiber fruits and vegetables and high-quality protein (fish or lean meat).

Another key: Do an hour of exercise at least five times a week. A good program for most people is 45 minutes of aerobic exercise — such as walking, biking or swimming — and 15 minutes of light weight lifting.

Reason: Regular exercise encourages weight loss and increases your body’s sensitivity to insulin. This effect only lasts a short time, however, which is why it’s important to exercise often.

For many, these steps will be enough to prevent diabetes. If your body’s ability to respond to insulin is 75% of normal and you can lower your insulin resistance by 25% through diet and exercise — a typical response — then your blood-sugar regulation will be brought back in balance.