Physical activity and weight loss are independent predictors of improved insulin sensitivity following energy restriction

Objective The role of physical activity and the joint effect with sleep duration on insulin sensitivity (IS) during energy restriction followed by weight maintenance were determined. Methods One hundred and two subjects (28 males) (mean ± SD age: 40 ± 9 years; BMI: 31.9 ± 3.0 kg/m 2 ) followed a very‐low‐energy diet for 8 weeks, followed by a 44‐week period of weight maintenance. Body composition (three‐compartment model based on body weight, total body water, and body volume), physical activity (accelerometry), sleep (questionnaire, Epworth Sleepiness Scale), and fasting plasma insulin and glucose concentrations were assessed before the diet and at 8, 20, and 52 weeks after the start. Results Compared to baseline, IS was improved significantly after 8 weeks ( P  < 0.001) and was higher after 20 weeks ( P  < 0.001) and 52 weeks ( P  < 0.05). After 8, 20, and 52 weeks, 23% ( P  < 0.01), 19% ( P  < 0.05), and 13% ( P  < 0.05), respectively, of the variance in IS improvement was explained by weight loss percentage and change in physical activity counts. Conclusions Maintaining daily physical activity during energy restriction is as important as weight loss itself in the improvement of IS; there was no additional effect of change in sleep duration. During weight maintenance, improved IS is maintained better if physical activity returns to baseline or higher.