Increased muscle dynamic endurance associated with weight reduction on a very-low-calorie diet

To assess muscle function after a period of negative energy balance, 32 obese women were placed on a 544-kcal/d, high-protein diet for 4 wk. Weight loss was associated with a decrease in the waist-to-hip-circumference ratio (WHR) and significantly higher emptying of abdominal than gluteal fat cells. The low-calorie regimen was associated with a significant increase in isokinetic muscle endurance, a decrease in glycogen concentration, and an increase in glycogen synthase (GS) activity and its fractional velocity (FV). The GS activity and its FV were negatively correlated with the WHR before treatment whereas their subsequent increase was correlated with the decrease in WHR. Dietary treatment produced a decrease in the isokinetic muscle strength, which was correlated with the reduction in lean body mass. The improvement in dynamic endurance observed after energy restriction parallels not only the increase in GS activity in muscle but also the decrease in glycogen stores and glucose oxidation, and most probably depends on the increased utilization of fatty acids.