The study found men in the study that exercised 30 minutes a day lost an average of about 8 pounds over three months compared with an average of 6 pounds for those who exercised 60 minutes a day.
Scientists say the surprising results may be due to the fact that 30 minutes of exercise left participants with the energy to do more.
Also, the 60 minutes of exercise daily may have left participants hungry and therefore they ate more, resulting in fewer pounds lost.