The energy cost of aerobic exercise in fed and fasted normal subjects

It has been claimed that there is a prolonged thermogenic effect of aerobic exercise although the evidence is by no means conclusive. We have therefore studied the thermogenic effect of moderate aerobic exercise in the fasted and fed state in four lean subjects during weight maintenance. Exercise was performed at a constant rate on a bicycle ergometer during the initial 20 min for four successive hours. The first two exercise periods were in the fasted state while the last two followed an 800 kcal (3.4 MJ) mixed meal. Oxygen uptake increased 22% over the 165 min after the meal on rest days (p less than 0.001). There was a significant but similar elevation of mean O2 uptake during 40 min postexercise by 13.6% in both the fasted (p less than 0.001) and fed state (p less than 0.001). Sixty minutes after ceasing exercise mean O2 uptake was not different from preexercise levels (p greater than 0.05). We conclude that there is no prolonged thermogenic effect of moderate repeated aerobic exercise in weight-maintaining lean subjects. In addition there was no interaction between exercise and dietary induced thermogenesis.