People who exercised for just half an hour a day lost more than one-third of their body weight when compared to people who were involved in long work out sessions, according to a new study conducted by researchers at the University of Copenhagen.

The study is published in the Scandinavian Journal of Public Health.

The scientists also found that people who were a part of short exercise sessions were happier, energized and motivated to lead healthier lifestyles. On the other hand, people associated with a full hour of hard fitness training were more likely to feel drained out.

The team arrived at the conclusion after studying 60 reasonably obese and fit Danish men for 13 weeks. Half of the men were asked to exercise vigorously for 30 minutes a day via jogging, cycling or cross training while the other half were told to exercise for a full hour, daily.

At the end of the study period, they found that men who exercised for half an hour lost an average of 3.6 kg over the three month period while those who exercised for an hour lost just 2.7 kg.

Dr Astrid Jespersen, one of the authors of the study, said that the findings could help motivate people who normally hate exercise.

 "The subjects in the test group that exercised the least talk about increased energy levels and a higher motivation for exercising and pursuing a healthy everyday life. They take the stairs, take the dog for an extra walk or cycle to work," Jespersen said.

"In contrast, the men who exercised for one hour a day, after training, felt exhausted, demotivated and less open to making a healthy change. We are thus seeing that a moderate amount of exercise will significantly impact the subjects' daily practices."

Professor Bente Stallknecht, who led the research at the faculty of health and medical sciences at University of Copenhagen, said that the results were surprising that moderate exercise were more beneficial than longer sessions.

"Our motivation basically stems from the interest to examine if the calories combusted during an exercise intervention are compensated by the body - for example through an increase in food intake and/or a decrease in physical activity level during the rest of the day, Stallknecht said.

"Surprisingly, we found indications of a reverse compensation in the moderate dose exercise group indicating that they became more physically active also outside the exercise program."