Researchers at the Faculty of Health and Medical Sciences, University of Copenhagen, followed 60 heavy, but healthy Danish men for 13 weeks.
30 participants were assigned to engage in exercise for one hour per day, wearing a heart-rate monitor and calorie counter. The other 30 participants were assigned to 30 minutes per day. The team found that 30 minutes of daily exercise was enough to lose weight.
Mads Rosenkilde, Ph.D. student, Department of Biomedical Sciences said: "On average, the men who exercised 30 minutes a day lose 3.6 kilo in three months, while those who exercised for a whole hour only lost 2.7 kg. The reduction in body mass was about 4 kg for both groups."
"Participants exercising 30 minutes per day burned more calories than they should relative to the training program we set for them. In fact we can see that exercising for a whole hour instead of a half does not provide any additional loss in either body weight or fat. The men who exercised the most lost too little relative to the energy they burned by running, biking or rowing. 30 minutes of concentrated exercise give equally good results on the scale."
According to the researchers, one explanation for their findings is that half an hour of exercise is so doable that study participants had the desire and energy for more physical activity after their daily exercise session. Furthermore, those who exercised for 60 minutes per day probably ate more, thus their weight loss was slightly less than anticipated.
"The participants in our study trained every day for three months. All training sessions were planned to produce a light sweat, but participants were expected to increase the intensity and give it gas three times a week.
Another interesting scenario is to study exercise as a form of transport. Training is fantastic for your physical and mental health. The problem is that it takes time. If we can get people to exercise along the way - to work, for example - we will have won half the battle."