Getting a good night's sleep is associated with helping you lose weight, a new study has found.

The study of US nurses found those who slept longest were slimmer than those who got less sleep.

The findings were presented at the American Thoracic Society International Conference in San Diego, and the author said:

"When we analyzed 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) 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."

He noted that BMI (body mass index) is linked to length and quality of sleep in a surprisingly consistent fashion.

BMI is calculated by dividing weight in kilograms by the square of height in meters. Obesity is defined as having a Body Mass Index (BMI) of 30 or more.

Researchers suggest that lack of sleep affects hormone levels that can trigger hunger and slow down your metabolism - for example, reducing the amount of leptin, sometimes known as the satiety hormone - and could thereby cause those individuals to eat more. Previous research has also shown people who sleep less than seven to nine hours a night are up to 75 per cent more likely to be obese.

Stress is also linked to playing a role in both reducing the length and quality of sleep and increasing eating and other behaviors that may result in weight gain.

The study author said: "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."

His researchers analyzed the sleep, activity and energy expenditures of 14 nurses who had volunteered for a heart-health program.

Surprisingly, 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, a total of 3,064 against 2,080. But those additional energy expenditures did not manifest in reduced weight.

Study details: American Thoracic Society's International Conference, San Diego, May 15-20, 2009. News release, American Thoracic Society.

Sleep is an essential way of resting, recharging and nourishing the body and brain. The amount of sleep required varies from person to person, depending on age, lifestyle and health. Try to get adopt a consistent sleep pattern that includes sleeping at the same time every night, and getting at least a few hours of good quality, deep sleep.