People trying to lose at least 10 pounds were more likely to succeed if they got enough sleep, U.S. researchers have found.

Traditionally, weight loss focused on diet and exercise changes. Now researchers are testing how factors like sleep, stress and depression that are tied to obesity also relate to weight loss.

"This study suggests that when people are trying to lose weight, they should try to get the right amount of sleep and reduce their stress," said the study's lead author, Dr. Charles Elder, an investigator with the Kaiser Permanente Center for Health Research in Portland, Ore.

"Some people may just need to cut back on their schedules and get to bed earlier. Others may find that exercise can reduce stress and help them sleep. For some people, mind/body techniques such as meditation also might be helpful," he suggested.

For the study published in Tuesday's online issue of the International Journal of Obesity, 427 obese adults were counseled about lifestyle changes over a 26-week period.

Recommendations included:

• Cutting 500 calories a day to lose 0.5 to two pounds each week.

• Eating a low-fat diet rich in fruits, vegetables and whole grains.

• Adding exercise time to reach 30 to 60 minutes every day and at least 180 minutes a week.

Participants were also asked about sleep time, depression, screen time in front of TV and computers, and stress.

Sleep, stress and weight loss

During the study, participants lost an average of almost 14 pounds.

People with the lowest stress levels who also got more than six hours, but not more than eight hours, of sleep were most likely to lose at least 10 pounds, the team found.

Experts say most adults need six to eight hours of sleep a night to feel refreshed and to perform optimally through the day.

"These results suggest that early evaluation of sleep and stress levels in long-term weight management studies could potentially identify which participants might benefit from additional counselling," the study's authors concluded.

A holistic view of health that considers diet, exercise, smoking, sleep, and controlling stress is important, said Dr. David L. Katz, director of the Prevention Research Center at Yale University School of Medicine in New Haven, Conn.

"Anyone who has ever tried to lose weight probably could have said much the same from personal experience. Similarly, weight loss reduced stress and depression. This, too, is suggested by sense and common experience, as it is affirmed by the science reported here," Katz told Health Day News.

A second part of the study is now looking at how the participants maintained their weight loss for another six months.

The study was funded by the U.S. National Institutes of Health's National Center for Complementary and Alternative Medicine.