Sleep quality, quantity linked to body weight
Instead of adjusting your diet to lose weight, you might want to try adjusting your sleep. And get treatment for sleep apnea, too, if you have it.
Two American studies have found a clear link between sleep and body mass index (BMI). While the first associates the duration of slumber with BMI, the second shows that severe obstructive sleep apnea, a disorder wherein breathing when asleep is disturbed, could lead to weight gain.
Under the first study, researchers from the University of Washington Sleep Institute, reviewed data on 1,797 twins, 634 being twin pairs and 529, one of the twins. In the twin pairs, 437 were identical twins, born from the same egg, and 150 were fraternal twins, born from two separate eggs. The zygocity of 47 twin pairs couldn’t be determined. The average age of the subjects was 36.8 years, with a majority being females.
The researchers asked the subjects about the duration of their sleep and their height and weight. They then calculated their BMI, an indicator of optimum weight for a particular height. After adjusting for genetic and other factors, the researchers found that those who slept for between 7 and 8.9 hours daily had a lower BMI than did those who slept longer or fewer hours.
Even the BMI of identical twins was found to vary if their sleep patterns differed.
The average BMI of those who got adequate sleep was 25 against 26.4 for those who slept less or more. Dr Nathaniel Watson, the lead author of the study, said, “The findings of the study point towards an environmental cause of the relationship between sleep duration and BMI. Results were robust enough to be present when the sample was limited to identical twins.”
The second study, by a team from the University of Arizona College of Medicine in Tucson, found that people with severe obstructive sleep apnea were more likely to gain weight than were their counterparts with a milder form of the disorder. Under this study, the researchers determined the severity of the disorder in 3,001 subjects by rating them on the apnea-hypopnea index, based on the frequency of episodes where breathing stops completely (apnea) and partially (hypopnea). Those with ratings above 15 on the index were found to have greater BMI that those between 5 and 15.
Lead author Dr Mark Brown said, “Obesity is a known risk factor for obstructive sleep apnea. However, it is hypothesised that the effects of the disorder itself may predispose patients to weight gain.”
Both the studies were presented at SLEEP 2009, the 23rd annual meeting of the Associated Professional Sleep Societies in Seattle.
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