Energy cost of walking in boys who differ in adiposity but are matched for body mass.

PURPOSE: To compare the energy cost of treadmill walking, in pairs of obese and lean adolescents who were matched for total body mass. METHODS: Metabolic energy expenditure was determined at 67, 83, and 100 m.min-1, in nine obese and nine nonobese 11- to 18-yr-old boys. Total adiposity and fat distribution in the trunk and limbs were assessed using DXA. RESULTS: There were no intergroup differences in the net (exercise minus rest) energy cost at the two lower speeds, but the obese boys expended more energy at 100 m.min-1 (12%, P < 0.05). Heart rate was consistently higher in the obese boys: 18% at 67 m.min-1, 22% at 83 m.min-1, and 28% at 100 m.min-1. Pooling all subjects together, body mass, rather than adiposity, was the main predictor of energy cost: 89.1%, 76.3%, and 62.1% (P < 0.05 for all) of the total variance at 67, 83, and 100 m.min-1, respectively. The variance explained by total body fat was only 2.1%, 8.4%, and 16%, respectively. There was no relationship between [OV0312]O(2net) and the proportion of fat in body segments. CONCLUSION: It is total body mass, more than adiposity (total and regional) per se, that affects the energy cost of locomotion in obese boys.