Researchers have claimed that more body fat could be lost by completing a shorter workout than a longer one and challenging accepted wisdom on weight loss and training regimes.
A study of healthy but sedentary men, aged between 20-40, has found that a test group who exercised for half an hour a day, lost more weight than a group that exercised for 60 minutes a day, News.com.au reported.
In the study, which was accepted for publication, the researchers from the University of Copenhagen recruited 64 "moderately overweight" subjects who never normally engaged in any regular exercise.
The subjects were randomly chosen to participate in either "high dose" or "low dose" 13-week aerobic exercise programs, mostly based around running or cycling.
A further control group participated in no exercise at all.
All were required to stick to, and monitor, their usual diets.
The non-exercising group recorded no noticeable weight change, while both exercise groups lost weight.
But the researchers were mystified by what they found: individuals in the group exercising 60 minutes a day lost on average 2.7 kg of body weight after 13 weeks, while the 30-minute team lost on average 3.6kg.
"Somewhat surprisingly," the report states, "we found no additional benefit from doubling the exercise dose. Therefore, we challenge the basis for the current recommendations regarding exercise for weight management.
"We conclude that a similar meaningful loss of body fat was obtained regardless of exercise dose."
The report is not anti-exercise. It found that exercising 30 to 60 minutes a day produced "clinically meaningful" health results in both groups, and led to real weight loss outcomes.
One explanation for the men who exercised more, but lost less, is that they may have secretly increased their food consumption because they got hungrier after doing more. If so, they did not declare it on their diet charts.
The study is published in the American Journal of Physiology.