Walking at the moderate pace of 4 km/h appears as beneficial to fat oxidation as more strenuous exercise in prepubertal boys, according to Claudio Maffeis, M.D., of the Department of Pediatrics at University Hospital, Verona, Italy.
Twenty-four boys, aged 9–11 years, with an average body mass index of 25.5 were given a treadmill test, their respiratory exchange measured by indirect calorimetry while they walked at 4, 5, and 6 km/h. The investigators also measured the boys' maximal oxygen uptake. All the boys reported a sedentary lifestyle, spending 2 hours per week in recreational organized physical activity after school.
Energy expenditure and carbohydrate oxidation increased progressively as the treadmill speed was increased. However, the fat oxidation rate did not change significantly when walking speed increased (J. Clin. Endocrinol. Metab. 2005;90:231–6).
After adjusting for fat-free mass, a partial regression analysis demonstrated that energy expenditure during walking correlated with adiposity in boys, the researchers said. In another partial regression analysis, they found a significant association between adiposity and the fat-to-carbohydrate oxidation rate during walking at all three speeds.
“Therefore, at similar exercise intensities, the greater the adiposity of the body, the higher the energy expenditure and the proportion of carbohydrate in the fuel mix that oxidized during walking,” the researchers said.
Low-intensity exercise may be more acceptable to overweight children and may not lead to the higher carbohydrate oxidation tied to later sedentary behavior and increased appetite, they added.