Energy cost of physical activity on a metabolic ward in relationship to obesity.

The energy cost of physical activity on a met- abolic ward was derived from the difference between the energy requirement to maintain body weight on a metabolic ward and sedentary 24-h energy expenditure measured in a respiratory chamber in 56 nondiabetic male subjects. The cost of physical activity was negatively correlated with body weight (r = -0.67, P < 0.000 1) and with percent body fat (r = -0.48, P < 0.0005). In a subgroup of 15 subjects selected for strict weight stability (rate of daily weight change < ±35 g/d), similar negative cor- relations were observed between energy cost ofactivity and body weight (r = -0.61, P < 0.01) and percent body fat (r = -0.51, P = 0.05). The ratio of active to sedentary energy expenditure, an index ofphysical activity, was also negatively correlated with body weight and percent body fat (r = -0.74, P < 0.002 and r = -0.61, P < 0.02, respectively). These results suggest that heavier subjects on a metabolic ward are less active and expend less energy in physical activity than do lighter subjects. Am JClin Nutr l99l;53:l368-7l.