May 15, 2009 -- If you are trying to lose weight , a good night’s sleep might help.

A new study found a link between sleep and weight. Study participants who were so-called short sleepers (meaning they got less than six hours per night) tended to have on average a higher body mass index , or BMI, than long sleepers.

The small study, presented at the American Thoracic Society’s International Conference in San Diego, was conducted with 14 nurses at Walter Reed Army Medical Center. Nurses received counseling on nutrition, exercise, stress management , and sleep improvement through the program.

The participants wore armbands that measured total activity, body temperature, body position, and other indicators of rest and activity.

The average BMI for short sleepers was 28.3. That compares to an average BMI of 24.5 for long sleepers. The BMI range for normal weight is considered to be 18.5-24.9 and for overweight 25.0-29.9. BMI is calculated from a person's weight and height and is an indicator of body fat.

Surprisingly, the overweight participants were significantly more active than their normal-weight peers. The overweight participants took an average of 13,896 steps per day, compared to 11,292 for normal-weight participants. The overweight participants also burned nearly 1,000 more calories per day on average than their normal-weight peers.

“We found so many interesting links in our data,” lead researcher Arn Eliasson, MD, says in a written statement. “Primarily, we want to know what is driving the weight differences, and why sleep and weight appear to be connected."

There are several possible reasons, Eliasson says. Lack of sleep may disrupt natural hormonal balances, triggering overeating. Stress could also be a factor -- contributing to less sleep and more eating in the same people.

He says that "higher perceived stress may erode sleep. Stress and being less rested may cause these individuals to be less organized than normal-weight individuals, meaning they would have to make more trips and take more steps to accomplish the same tasks. This might add to their stress and encourage other unhealthy behaviors, like stress eating."

Eliasson and colleagues are planning more studies to investigate the link between stress, sleep, and metabolism.