A good night's sleep may help you lose weight

According to the study, body mass index (BMI) is linked to length and quality of sleep in a surprisingly consistent fashion.

During the study, researchers analysed the sleep, activity and energy expenditures of 14 nurses who had volunteered for a heart-health programme at Washingon's Walter Reed Army Medical Centre, where the nurses were employed.

The programme included nutritional counselling, exercise training, stress management and sleep improvement. Each participant wore an actigraphy armband that measured total activity, body temperature, body position and other indices of activity and rest.

"When we analysed our data by splitting our subjects into 'short sleepers' and 'long sleepers', we found that short sleepers tended to have a higher BMI, 28.3 kg/m2, compared to long sleepers, who had an average BMI of 24.5. Short sleepers also had lower sleep efficiency, experienced as greater difficulty getting to sleep and staying asleep," said lead author Arn Eliasson, of of the Integrative Cardiac Health Project at Walter Reed.

The researchers also found that overweight individuals tended to be more active than their normal weight counterparts, taking significantly more steps than normal weight individuals: 14,000 compared to 11,300, a nearly 25 percent difference, and expending nearly 1,000 more calories a day -- 3,064 versus 2,080.

However, those additional energy expenditures did not manifest in reduced weight.

"We found so many interesting links in our data. It opens up a number of possibilities for future investigation. Primarily, we want to know what is driving the weight differences, and why sleep and weight appear to be connected," said Dr. Eliasson.

Dr. Eliasson postulates that getting less sleep might disrupt natural hormonal balances and could thereby cause those individuals to eat more.

Stress may also play a role in both reducing the length and quality of sleep and increasing eating and other behaviours that may result in weight gain.