Does regular exercise help to prevent type 2 diabetes?

Yes, regular exercise of at least moderate intensity pro- vides some protection against the onset of type 2 dia- betes. Exercise improves insulin resistance and thereby makes insulin more effective at removing glucose from the blood. In patients with prediabetes (see Question 9), exercise can prevent the progression  of elevated glu- cose values toward the frankly diabetic range, or even restore them to normal. Exercise also consumes calories from those stored in the exercising muscle as starch (glycogen)  and  the  need  to  replenish  these  stores draws glucose out  of  the  bloodstream  and  thereby reduces the  circulating levels.  Exercise also helps to maintain a healthy body weight and avoid the weight gain  that  can  lead  to  diabetes

although it is not as certain that exercise is as helpful in  promoting weight reduction. Weight  reduction is much more  dependent on restriction of food intake. However, exercise is clearly important in maintaining weight loss. Finally, it is worth noting that exercise has beneficial effects on the other risk factors that combine with diabetes to cause vascular disease. For  example, exercise increases the good (or HDL)  cholesterol and improves levels of  other  blood  fats, while lowering blood pressure and enhancing cardiovascular (i.e., heart and blood vessel) conditioning.