Gas exchange during exercise in obese children

Twenty-three obese children, aged 9 to 14 years, ranging in percentage overweight from 26% to 83% (median 51.6% +/- 16.3%), and 37 normal-weight children, matched for sex, age and height, performed a maximal exercise test on a treadmill. Cardiorespiratory performance was assessed by determination of the ventilatory anaerobic threshold (VAT) expressed in ml O2/min per kg and as a percent of maximal oxygen uptake (% VO2max). VAT and VO2max related to body weight were significantly lower (P less than 0.01) in the obese than in the normal-weight children. VAT % VO2max was similar in the two groups. A significant correlation was found between VAT and VO2max both in the obese (r = 0.85) and in the control groups (r = 0.79). The habitual level of physical activity was lower in the obese subjects compared to the control subjects (P less than 0.001). In conclusion our study shows that physical fitness of overweight children is quantitatively lowered and that it can be assessed by VAT. VAT does not require a maximal test and is particularly useful in the ergometric study of subjects with exercise intolerance.