THE ENERGY REQUIREMENTS IN INDIVIDUALS WITH MENTAL RETARDATION

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To characterize energy metabolism in individuals with mental retardation (MRs), We meaured energy cost at several physical activity levels (basal, supine, siffting, standing, and walking at 30,50 and 70 m/min), maximal oxygen consumption (Vo_2max), and body composition in 23 male MRs and the same number of volunteer male controls. Both groups were individually matched for age, body height, and body weight. Energy costs were measured by the Douglas bag technique. The recently developed sulfur hexafluoride (SF_6) dilution technique was employed for measuring body composition.In addition, 3-dimensional accelerometry was used for evaluating body movements, and plasma indices of macronutrients were also measured. Results : The energy cost of MRs, when sitting, standing, and walking at 30 and 50 m/min, was significantly higher than that of controls (p<0.05), while the basal and resting metabolic rates were similar in both groups. Vo_2max was significantly lower (P<0.05) in MRs than controls. Accelerometry demonstrated excessive movements in MRs, which may explain their higher energy cost of exercise. By contrast, no significant difference was observed in percent body fat and lean body mass. Concentrations of plasma total cholesterol, triacylglycerols and albumin were significantly lower in MRs compared with controls.Our findings suggest that MRs are burdened with energy metabolism less economical than non-MRs. A limited physical activity in their daily life may be the cause. These characteristics of MRs' energy metabolism should be considered for planning their proper dietary schdules and physical activity programs