Metabolic rate during and after aerobic exercise in post-obese and lean women

The effect of aerobic exercise (cycling on bicycle ergometer for four 10-min periods/60-80 per cent max VO₂) on energy expenditure following the activity was investigated in 16 post-obese and 16 lean control women over 24 h and shorter periods. In addition, net energy expenditure during aerobic exercise was compared to that during prolonged mild activity (stepping for four 30-min periods at 12 steps/min). The measurements were made in a room respirometer. Aerobic exercise did not significantly stimulate the 24-h resting metabolic rate of either the post-obese (3 per cent, 50 kcal) or lean controls (2 per cent, 30 kcal), nor was there any significant stimulation over shorter periods: during waking hours RMR was non-significantly increased by 5 per cent in both the post-obese and lean controls. Sleeping expenditure remained the same in the post-obese and was decreased by 2 per cent in the lean controls. All subjects found the aerobic exercise to be quite uncomfortable, yet in both groups the net cost was smaller than that of prolonged mild exercise which was found to be acceptable (post-obese: aerobic 180 kcal, mild 250 kcal; lean controls: 220 kcal, 290 kcal). It is suggested that prolonged mild activity (eg, as in walking frequently) is more appropriate in increasing energy expenditure as a means of preventing or controlling obesity. Total expenditure at each level of activity is also expressed as multiples of BMR calculated from FAO/WHO/UNU (1985) prediction equations and from measured sleep values. The results show that the equations overestimated BMR in the post-obese.