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Could we help rein in the obesity epidemic by keeping our bedrooms cooler at night and getting a better night's sleep? Italian researchers say these factors are related to the risk of obesity.
In their study, published in the International Journal of Obesity, Dr Simona Bo and colleagues at the University of Turin in Italy followed nearly 1,300 middle-aged adults over six years. During that time, 103 became obese.
When the researchers looked at a number of environmental factors, they found that sleep habits were related to the risk of obesity. For each hour of sleep people typically got each day, the odds of their becoming obese declined by 30%, even with other factors like physical activity levels and TV watching taken into account.
Then there was home temperature. Compared to people who kept their homes cooler in winter, those who liked a toastier home were twice as likely to become obese.
Diet still a factor
Diet, of course, also mattered: the more often people ate at restaurants each week, the greater their likelihood of becoming obese. And those who got little fibre in their diets were at greater risk of developing abnormally high blood sugar levels.
None of this proves that turning down the heater or sleeping more will make people thinner.
"I wouldn't say to anyone that if you turn down your heater in winter, you'll lose weight," said Dr David B. Allison, director of the Nutrition Obesity Research Centre at the University of Alabama at Birmingham.
On the other hand, things like home temperature and sleep habits are lifestyle factors that "you can play with" in managing weight, said Dr Allison.
Why indoor temperature matters
Dr Allison says it's fairly simple: the body burns more kilojoules when it has to work to maintain a stable temperature.
To best of his knowledge, Dr Allison said, this latest study is the first to connect home temperatures with risk of obesity.
As for sleep, a number of past studies have linked excess weight and chronic sleep deprivation, typically defined as less than six hours per night. One theory is that the hormonal effects of sleep loss are to blame. Another is that sleep-deprived people may eat and drink more in an effort to boost their energy levels.
In his own 2006 study of air conditioning and obesity rates, Dr Allison cited a number of modern-life factors that could be contributing to rising obesity, including widespread use of antidepressants and other medications that can promote weight gain, and industrial chemicals that may alter hormone activity.
"No one factor is going to explain the obesity problem," he said.
(Reuters Health, Amy Norton, February 2011)
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