Abstract P306: Skeletal Muscle Mass is Related to Physical Activity and Dietary Behavior in Adolescents

Abstract

Background: As the most abundant insulin-sensitive tissue, skeletal muscle plays a crucial role in systemic glucose metabolism. Physical activity and healthy diet are beneficial at preserving skeletal muscle in the elderly; however, their role on skeletal muscle mass in adolescents has not been reported. Objective: We hypothesized that higher physical activity and healthy diet behaviors are associated with greater skeletal muscle mass. Design: A cross-sectional, observational study in 640 healthy European and African American aged 14-18 years. Measurements: Diet was assessed by four to seven 24-h recalls, and physical activity was determined by 7-day accelerometry. Healthy diet behaviors included higher energy intake from protein, lower energy intake from fat, higher consumption of fruit, vegetable, whole grain foods and lower consumption of sweetened soft drinks. Fat-free soft tissue mass (FFM) and fat mass (FM) were measured using dual-energy X-ray absorptiometry. The residual derived from the regression of FFM on height and FM was used as an index of skeletal muscle mass. This is an index independent of the influence from height and fat mass. Results: Multiple linear regression, adjusting for age, sex, race, and total energy intake, revealed that skeletal muscle mass was positively correlated with both moderate (P<0.001) and vigorous physical activity (p<0.001). In addition, skeletal muscle mass was positively correlated with energy intake from polyunsaturated fatty acid (p=0.023) and consumption of whole grain foods (p=0.029) while negatively correlated with energy intake from saturated fatty acid (p=0.003) and consumption of sweetened soft drinks (p=0.003). In the final model including all of the significant predictors, physical activity, energy intake from saturated fatty acid, and consumption of sweetened soft drink are all independent contributors to skeletal muscle mass. Conclusions: For the first time, our adolescent data suggest that engage in physical activity increase while greater consumption of saturated fatty acid and sweetened soft drinks reduce skeletal muscle mass.