Improved glucose tolerance after intensive life style intervention occurs without changes in muscle ceramide or triacylglycerol in morbidly obese subjects

Aim: This study investigated the effect of a 15-week life style intervention (hypocaloric diet and regular exercise) on glucose tolerance, skeletal muscle lipids and muscle metabolic adaptations in 14 female and 9 male morbidly obese subjects (age: 32.5 +/- 2.3 years, body mass index: 46.1 +/- 1.9 kg m-2). Method: Before and after the life style intervention, an oral glucose tolerance test was performed and a muscle biopsy was obtained in the fasted state. Maximal oxygen uptake was measured by an indirect test. Results: After the intervention, body weight was decreased (P < 0.05) by 11 +/- 1%, maximal oxygen uptake increased (P < 0.05) by 18 +/- 5% and glucose tolerance increased (P < 0.05) by 12 +/- 3%. Muscle glycogen was significantly increased by 47 +/- 14%, but muscle ceramide and triacylglycerol content remained completely unchanged. No sex difference was observed for any of these parameters, but during submaximal exercise a marked decrease (P < 0.05) of 15 +/- 2% in respiratory exchange ratio was seen only in females indicating an enhanced fat oxidation. Conclusion: Despite a marked weight loss and an improved aerobic capacity muscle ceramide and triacylglycerol remained unchanged after intensive life style intervention, and muscle lipids hence do not seem to play a major role for the improved glucose tolerance in these morbidly obese subjects. Interestingly, only the females improved fat oxidation during submaximal exercise after the intervention implying the presence of a sex-dependent response to intensive life style adaptation.