THE INFLUENCE OF DIET AND PHYSICAL-ACTIVITY ON INSULIN SENSITIVITY

This article reviews the effects of diet and exercise on insulin sensi tivity in patients with type II diabetes (non-insulin-dependent diabet es mellitus, NIDDM). Dietary caloric restriction operative through wei ght loss decrease the insulin resistance characteristic of the disease by increased glucose transport. The precise localization of this effe ct is unknown, as is the defect in the insulin signalling pathway in t ype II diabetes. Inherent problems are the inability to clearly separa te obesity and type II diabetes and methodological difficulties in the distinction of dietary effects from exercise-induced effects. The mec hanism of exercise-induced insulin sensitivity has gained considerable understanding through the detection of the glucose transporter molecu le GLUT-4 in muscle. It is now clear that the presence of insulin is n ot mandatory and mere electrical stimulation of the muscle produces si milar effects through distinct signalling pathways. Exercise-induced i ncreased blood flow and decreased vascular resistance may also play an important role. In contrast to these newer experimental data, clinica l studies and feasibility studies aimed to implement exercise as a val uable therapeutic measure in type II diabetes have failed to delineate promising long-lasting effects and can therefore not be generally rec ommended. Encouraging epidemiological data have recently been found wi th respect to the prevention of type II diabetes by increased physical activity in patients at risk.