Modern lifestyle diminished significantly the need of everyday exercise, which is probably one of the major factors leading to the development of several metabolic diseases including type 2 diabetes, hypertension and atherosclerosis with its deadly consequences. Epidemiological studies proved that higher levels of cardio-respiratory fitness are associated with lower mortality irrespective of fat stores. Physical activity reduces all-cause, cardiovascular as well as cancer associated mortality.
Beneficial effects of exercise on insulin sensitivity have been demonstrated in a short term as well as following a longer periods of physical activity. Moreover, regular physical activity has been shown to change the metabolism of adipose (fat) tissue. Adipose tissue is potent endocrine organ producing several proteins collectively called ‘adipokines’, several of which regulate insulin sensitivity in a negative while others in a positive way. Modification of gene expression and production of adipokines represents another possibility, how exercise improves insulin sensitivity, decrease pro-inflammatory state and mediate its wide spread beneficial effects.
Physical activity has a beneficial effect on insulin sensitivity in normal as well as insulin resistant populations. A single bout of exercise can increase insulin sensitivity for at least 16 h post exercise in healthy as well as type 2 diabetics (noninsulin-dependent diabetes mellitus) subjects. Physical training can be considered to play an important, if not essential role in the treatment and prevention of insulin insensitivity.
A moderate aerobic exercise program, without weight loss, can improve insulin sensitivity in both lean and obese sedentary adolescents. Many studies include both diet and exercise interventions, which makes it difficult to determine which intervention is most effective and best accepted by adolescents. There was a study done at the Baylor College of Medicine to determine whether a controlled exercise program, without any diet intervention and with no intention of weight loss, would improve fat distribution and sensitivity to insulin. The researchers concluded that exercise alone can increase fitness and improve insulin sensitivity, making an aerobic program like the one used in the study a potential useful tool in preventing obesity-related illnesses.
The subjects that went through a 12-week moderate aerobic exercise program consisting of four 30-minute workouts a week, increased fitness and improved insulin sensitivity in both lean and obese adolescents. During the exercise sessions, subjects worked out on a treadmill, elliptical or bicycle. The goal of each exercise session was to get the participants’ heart rate to increase to at least 70 percent of their maximum capacity.