Exercising after meals can help promote weight loss by boosting hormones that suppress appetite, say UK scientists.
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.”
The interesting thing here is what bodybuilders have been saying for a long time, that exercise actually reduces appetite overall, even if you do feel a little more peckish after.
The hormone thing is already well-established and I’m not sure why this is paraded as news, though here they give the added twist of “just after food”.
Thing is, the effect is there at ANY time, with a full stomach not being necessary to achieve the appetite-killing hormones.
I should also add it is a little bizarre to triumphantly point out that people felt less hungry after A. an increase in such hormones and B. they had just eaten breakfast!
So why do I even mention this article?
Partly as it is a classical example of non-news dressed up as some great breakthrough. I’d even go as far as to say the article is likely to be discouraging for some, as who likes the idea of exercising on a full stomach?
I also mention it as it flies in the face of 3 well-established bodybuilding canards:
1. Maximum fat ripping is achieved while exercise on an EMPTY stomach – this is too well-proven by bodybuilders getting RESULTS to be ignored.
2. Not all calories are equal – for example just WHAT did the volunteers eat for breakfast? If they ate high-fat meals such as bacon and eggs then they would suppress their appetite more than if they ate jam on toast for example.
3. Swimming has long been known for the opposite effect. Because swimming tends to lower the body’s core temperature (short of swimming in a very warm bath) the body burns more calories to maintain its natural heat balance. This in turn leads to excessive “munchies” afterwards
The result, even if you pre-warn trainees before-hand, is that they invariably head for the high-sugar snacks, the ‘high octane’ fuel the body wants to help it stabilize.
So strong is this effect, even hours after the swimming, that I don’t recommend this form of exercise for slimming, as it’s a real “diet breaker” which in turn can crush confidence. In all other respects it is one of the best types of exercise there is, but for “ripping” I cannot recommend it.
In addition there is more involved than meets the eye at first glance. For example exercising on a full stomach is not merely uncomfortable but people are not machines.
It is one thing to ponder over the results of people on exercise bikes for an hour, a whole new thing to get people on an exercise bike for an hour in the first place!
The article pays lip service to this at the end but it’s very important – if you were NOT part of a controlled study, I double-guaran-darn-tee you that you would not be on that bike for a full hour.
That’s presuming you could be coaxed onto it in the first place!
Half an hour of actual exercise beats the pants off of 10 minutes then quitting before you puke!
Such studies are useful in that they can add to our knowledge, but no, exercise on a full stomach is not recommended