In a long-term study of middle-aged women, those who slept 5 hours or less each night were 32 percent more likely to gain a significant amount of weight (adding 33 pounds or more) and 15 percent more likely to become obese during 16 years of follow-up than women who slept 7 hours each night.

This level of weight gain -- 15 kg, or 33 pounds -- is "very clinically significant in terms of risk of diabetes and heart disease," Dr. Sanjay Patel of Case Western Reserve University told Reuters Health.

Women who slept 6 hours nightly were 12 percent more likely to experience major weight gain and 6 percent more likely to become obese compared with those who slept 7 hours each night. Women who said they slept for 5 hours or less each night, on average, weighed 5.4 pounds more at the beginning of the study than those sleeping 7 hours.

After accounting for the influence of age and weight at the beginning of the study, women who slept 5 hours or less each night gained about 2.3 pounds more during follow-up than those who slept 7 hours nightly. Women who got 6 hours of shut-eye each night gained 1.5 pounds more than those who slept 7 hours nightly, reports Reuters.

According to Medical News Today, Dr Patel said he believes that people who sleep well fidget more during their waking hours - this helps them consume more calories. It is also most likely that hormones are tweaked in such a way as a result of how much we sleep - and this has a bearing on how many calories we burn off each day.

In order to stay/get slim, people have to focus on three factors:
-- Adequate sleep
-- Nutrition
-- Physical activity

Ask any professional sportsperson what the secret of top fitness is, and they will all say it is a combination of good training, eating the right foods and sleeping well - get one of those three factors wrong and you seriously undermine your chances of winning a race.

"We don't really understand why sleep deprivation predicts weight gain at this point, but it could be that because they are more tired, the women are less likely to exercise ¡ª become couch potatoes, if you will," Dr. Patel suggested. "Or, sleeping deprivation may cause changes in a person's basal metabolic rate."

Safwan Badr, MD, chief of pulmonary medicine at Wayne State University in Detroit, Michigan, said that like many other findings of the prospective Nurses Health Study, these results ¡°should have a very important impact on medical practice.

"The practicing physician really needs to stress to her patient that getting a good night¡¯s sleep is not just a luxury," Dr. Badr told Medscape. "It¡¯s a mandatory way to improve your health," informs Medscape.