A 2012 study published in the American Journal of Physiology found that 30 minutes of daily exercise was just as effective at helping overweight adults lose weight as 60 minutes of daily exercise.
For the study, researchers from the University of Copenhagen studied 60 moderately overweight men who wanted to lose weight. Men were randomly assigned to one of two groups, a moderate aerobic exercise group or a high aerobic exercise group. The high-exercise group had to exercise hard enough to produce a sweat for 60 minutes a day, while the moderate group only had to exercise hard enough to produce a sweat for 30 minutes per day.
The study was conducted for 13 weeks, and, by the end of the 13th week, the men who exercised for 30 minutes per day had experienced similar, if not better, results than those who exercised for 60 minutes per day. In fact, the men who exercised for 30 minutes lost an average of two pounds more body weight than those who exercised for a full hour.
Researchers suggest that the men in the moderate group might have benefited from having more energy throughout the rest of the day, while those in the 60-minute group had little energy for the rest of the day and were less inclined to be physically active post-workout.