How Exercise Helps Relative to Diet and Weight Loss
The Centers for Disease Control and Prevention estimates that by 2050, one in three American adults could have diabetes. Exercise, whether aerobic or resistance-based such as weight training, is considered one of the most effective lifestyle habits individuals at risk can adopt to prevent potential cases from becoming actual cases. It has been shown that exercise has a greater protective effect for those at highest risk. In some instances, exercise has a greater beneficial effect than dietary modifications or even weight loss on the management of blood sugar.
Effects on Blood Sugar Regulation
Exercise causes skeletal muscle to be more sensitive to insulin, the chemical signal that tells cells to absorb glucose. As a result, exercise speeds the clearance of glucose out of the blood and into skeletal muscle cells, which need glucose in higher quantities during increased activity. Exercise also increases blood flow to muscles, thereby making more glucose available for the muscles to absorb. In older individuals, decreased insulin sensitivity, which is a lowered responsiveness of cells to insulin, is common. This is associated primarily with decreased levels of physical activity and is readily reversed through resumption or increase in exercise levels.
There is an alternate pathway, carried out by an enzyme called AMP kinase, that initiates glucose transport from blood to cells without the use of insulin. This is especially important and helpful in light of the prevalence of insulin resistance in those at risk for diabetes. Exercise is found to increase levels of AMP kinase.
Effects on Fat Metabolism
Certain storage and distribution patterns of fat are seen as red flags for health risks. Individuals who have the tendency to store fat around the abdomen are often found to have other health risk factors such as high triglycerides, high blood pressure and high blood sugar levels. The culprit here seems to be the portion of the abdominal fat that resides directly around the organs, known as visceral fat, as opposed to the subcutaneous portion, which is the fat just beneath the skin. The good news is that exercise is found to promote abdominal fat loss preferentially over fat stored in other areas of the body and also shrinks the size of subcutaneous fat cells.
Effects on Muscle Physiology
Muscle fibers change in response to exercise, adopting a form that is more sensitive and responsive to insulin. These exercise-induced muscle fibers also have higher capillary density and greater blood supply. All this adds up to lower blood sugar levels and a lowered risk of diabetes. The effects of exercise are not cumulative, and as with diet or any lifestyle habit, exercise must be maintained over time. However the short- to medium-term residual benefits include increased muscle mass and along with it the associated higher metabolic demand for blood sugar at all times, including during rest.