Objective: The study examined fat oxidation rates (FOR) during exercise in lean and obese pubescent children.
Design: Two groups of pubescent boys (13 lean: 12 ± 0.48 years old, BMI=18.56 kg/m2 ± 1.12; 17 obese: 12.1± 0.1 years old, BMI=26.68 kg/m2 ± 3.37 (p<0.001) performed a graded test on a leg cycle ergometer. The first step of the test was fixed at 30 W and power was gradually increased 20 W every 3 minutes 30 seconds. The average measurement of ventilatory gas was obtained during the last 30 seconds of each step which allowed us to calculate FOR vs exercise intensity.
Results: At low intensity, 0-30 % of VO2 peak, when Fat Free Mass is considered, FOR are identical for the two groups. At higher intensities, 40, 50 and 60% of VO2 peak, FOR is significantly higher in lean vs. obese boys.
Conclusion: The study confirms that obese pubertal boys have FFM decreased capacities to use fat during moderate exercise. The study suggests that obese boys have to practice physical activity at a lower intensity than healthy boys to enhance lipolysis and diminish adipose tissue and the consequences of obesity.