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.