If you want to lose weight, exercising for more than 30 minutes a day may be wasted effort, a new study from Denmark suggests.
In the study, participants who exercised for 30 minutes a day for three months lost just as much weight and body fat as those who exercised for an hour a day for the same time period.
This difference in weight loss was seen despite the fact that the 60-minute group burned twice as many calories, on average, as the 30-minute group.
The researchers were surprised by their results. It's possible those who were assigned to the 30-minute exercise group saw their training as more doable, and had the desire and energy for more physical activity afterward, the researchers said.
In addition, the people who spent 60 minutes exercising probably ate more, and therefore lost slightly less weight than anticipated, said study researcher Mads Rosenkilde, a doctoral student at the University of Copenhagen.
The study is published in the Aug. 1 issue of the American Journal of Physiology.
The study involved 60 overweight Danish men who had previously lived a sedentarylifestyle. About one-third were assigned to do 30 minutes of aerobic exercise a day at an intensity level high enough to produce a light sweat, one-third were told to do 60 minutes of aerobic exercise a day and the rest remained sedentary.
Participants in the exercise groups wore heart-rate monitors and calorie counters during training, and the program lasted 13 weeks.
On average, men who exercised 30 minutes a day lost nearly 8 pounds (3.6 kilograms) in three months, while those who exercised for a whole hour lost about 6 pounds (2.7 kg). The reduction in fat mass was about 9 pounds (4 kg for both groups).
Interestingly, the participants who exercised 30 minutes per day burned more calories than they were expected to, based on the training program that was set for them, the researchers said. And the men who exercised the most lost less weight than expected, based on the amount of calories they burned.
To exercise for health, the American College of Sports Medicine recommends 150 minutes of moderate exercise per week, or 75 minutes of vigorous exercise per week.
Pass it on: Thirty minutes of exercise a day works just as well as an hour of exercise for weight loss, a new study suggests.