Composition Of Lean Body Mass And Skeletal Muscle In Obese Children With Metabolic Syndrome

Abstract

Skeletal muscle is an important body compartment in obesity, because low energy expenditure results from decrease in the proportion of metabolically active tissues such as skeletal muscle. Although several studies suggested that lean body mass (LBM) composition may change in childhood obesity, less is known about the characteristics of LBM and skeletal muscle composition in obese children with metabolic syndrome (MS). PURPOSE:We investigated differences in LBM and skeletal muscle mass in upper arm, thigh and trunk among 3 groups of Japanese children: obese with MS, obese without MS and nonobese. METHODS:The cross-sectional areas (CSAs) of 2 (biceps brachii + brachialis and triceps brachii), 3 (quadriceps femoris, hamstrings, and adductors) and 4 (rectus abdominis, oblique, psoas major, and erector spinae) muscle groups located in upper arm, thigh and trunk, respectively, were determined in 6 obese with MS (9.9+/-2.0 years), 48 obese without MS (9.8+/-1.6 years) and 40 nonobese children (9.6+/-1.5 years) using magnetic resonance imaging. LBM was determined by air-displacement plethysmography. RESULTS:Obese with MS showed significantly greater absolute LBM than did both obese without MS and nonobese children by greater BMI (p<0.05). In contrast, relative LBM (LBM/body mass) was significantly lower in obese with MS than in the other 2 groups (p<0.05). In all muscles but hamstrings, oblique and erector spinae, the CSAs were significantly greater in obese with MS than in the other 2 groups even when matched for height (p<0.05). In both groups of obese children, correlations between LBM and CSAs of muscle in upper arm (r=0.78) and thigh (r=0.77) were greater than that between LBM and CSAs of trunk muscle (r=0.59). CONCLUSIONS:The present results indicate; (1) Obese with MS may have greater absolute amount of LBM and more upper arm, thigh and trunk muscle mass, but lower relative LBM and skeletal muscle mass, compared with both obese without MS and nonobese children; (2) Skeletal muscle composition may differ among obese children with MS, obese children without MS and nonobese children. Supported by Grant-in-Aid for Young Scientists (B) (No.20700562) from Japan's Ministry of Education, Culture, Sports, Science and Technology.