Exercising after meals can help promote weight loss by boosting hormones that suppress appetite, say UK scientists.
Exercise after meals can promote weight loss, the study suggests
Thanks to these hormones, active people feel less hungry immediately after exercise, and this carries through to their next meal, experiments suggest.
Even when their meals were bigger, sporty people gained fewer calories overall because they burned off more.
The Surrey University and Imperial College London work is published in the Journal of Endocrinology.
Twelve volunteers were fed the same breakfast.
An hour later, half of them worked out for an hour on an exercise bike while the other half sat quietly.
Both groups were left for another hour and then allowed to eat as much as they liked.
Unsurprisingly, people who exercised burned more calories than those who sat quietly, 492 kcal compared to 197 kcal.
And when given the chance to eat afterwards, people who had exercised tended to eat more, 913 kcal versus to 762 kcal.
However, when the amount of energy burned during exercise was taken into account, the sporty people took in fewer calories overall - 421 kcal compared to 565 kcal for the inactive group.
And levels of hormones called PYY, GLP-1 and PP, which tell the brain when the stomach is full, increased during and immediately after exercise.
Volunteers also said they felt less hungry during this time.
Researcher Dr Denise Robertson said: "In the past we have been concerned that, although exercise burns energy, people subsequently ate more after working out. This would cancel out any possible weight reduction effects of exercise.
"But our research shows that exercise may alter people's appetite to help them lose weight and prevent further weight gain as part of a healthy, balanced lifestyle."
Experts recommend people do at least 30 minutes of physical activity on five or more days a week.
Dr Ian Campbell, medical director of the charity Weight Concern, said: "This is an interesting study. Patients often report that they feel increased hunger and eat more after exercise.
"What this study shows is that, although total calorific intake is greater, the net result, because of the exercise taken, is a reduction in the net energy balance.
"Dieting is never easy. Increased physical activity is an essential part of any weight management programme, not just to expend more calories but also, as we see here, to help control our appetite too."
Dr John McAvoy, a GP with a special interest in obesity, said the study was a "significant contribution to understanding the complex mechanisms of energy balance".
"It will be of much more interest to the pharmaceutical industry than the general public at this stage, for the simple reason that most people view exercising so soon after eating as akin to putting your fingers down your throat," he added.
"For exercise to contribute to weight control it should be sustainable over the long term and enjoyment remains a critical factor to this end."