Investigation of insulin sensitivity in early diabetes III. The effect of a combined physical training and diet programme on body weight, serum lipids and insulin sensitivity in obese asymptomatic diabetics

Abstract

The effect of a physical training and low caloric diet (700 calories/day) for 4 weeks on insulin sensitivity in vivo, body weight and serum lipids was investigated in 10 obese asymptomatic diabetics (normal fasting plasma glucose and pathological glucose tolerance). Glucose tolerance and insulin secretion pattern were characterized by means of a 2h-glucose infusion test (12 mg/kg/min) primed by an initial injection of 0.33 g/kg glucose. Insulin responsiveness in vivo was estimated by means of a 1h-insulin infusion test (two 30-min. periods of 8 and 16 mU/kg insulin MC-Actrapid, primed by initial injection of 1 and 2 mU/kg, respectively). Under comparable steady-state insulin levels the decrease in plasma glucose and free fatty acids (FFA) was considered as estimate of insulin sensitivity in vivo. Physical working capacity (PWC170) was determined by means of a bicycle ergometer test in stepwise working loads. The training programme consisted of daily 15 min. bicycle ergometer training periods (75% of the maximal working capacity) in the morning and a 1 h mild physical training on a bicycle in the afternoon. After the combined training and diet programme the mean decrease in absolute and relative body weight amounted to 11.9 +/- 1.07 kg and 16.7 +/- 1.2%, respectively. There was a significant decrease of plasma triglycerides whereas the decrease in cholesterol was modest. Physical fitness increased by delta PWC170 of 31.1 +/- 11.6 W. In addition, the combined training and diet programme for 4 weeks resulted in a significant improvement of insulin sensitivity in vivo as indicated by an augmented insulin-induced decrease in plasma glucose and FFA (17.60 +/- 3.91%, vs 36.40 +/- 5.54%; p less than 0.05 and 35.90 +/- 6.95% vs 56.50 +/- 3.63%; p less than 0.05; respectively). Our findings provide direct evidence that physical training and low caloric diet enhance insulin sensitivity in vivo. From the practical point of view our results suggest the potential benefits of physical training in the treatment of obese asymptomatic diabetics.