IS ENERGY COST OF WALKING RELATED TO FAT DISTRIBUTION IN ADOLESCENT BOYS?

Abstract

Obese children and youth often do not perform activities at par with their leaner peers. It is possible that such a deficiency is due to a high metabolic cost of various activities. While the metabolic cost of walking is excessive in obese children and youth, it is unclear whether the distribution of fat among body segments contributes to such differences. PURPOSE This study was intended to determine whether the distribution of fat in the body contributes to metabolic cost of walking in young males. METHODS Eighteen males ages 11 to 18 years took part. They were pair-matched for total body mass but had a different amount of total body fat. Each pair included an obese and a lean boy. Body mass was almost identical in the two groups (71.25±15.25 and 71.84±15.49 kg for lean and obese subjects, respectively). Testing was done in the morning, following 12 hours of fasting. VO2 at rest and O2 cost of walking on the treadmill were measured. Each subject performed three 4-min walks at three different speeds: 4, 5 and 6 km/h. All walks, the order of which was assigned randomly, were at zero slope. VO2 was measured breath-by-breath and 30-sec averages of the last minute of exercise were used to calculate VO2net (exercise minus resting VO2). Body composition and fat distribution were assessed using DXA (Hologic QDR 4500A). RESULTS The proportion of total body fat in the abdomen was considerably higher in the obese group (42% vs 29%), but in the legs it was similar in the obese and the lean groups (38% vs 37%, respectively). In spite of inter-group differences in fat distribution, the relation between VO2net and the proportion of total body fat in the abdomen, legs and arms was similar between the pairs, in each of the three speeds. CONCLUSION The energy expended during walking at the three selected speeds is not related to the amount of fat in each body part, when expressed as a proportion of total body fat in lean and obese children and adolescents.