Here's a good excuse to crank up the thermostat, stoke the fire, or put on an extra layer: According to a new study, people who keep their houses toasty tend to be slimmer than people whose houses are cooler.
Researchers looked at the habits and weight of more than 100,000 English people, based on surveys the people took each year over 13 years. People who lived in houses at or above about 73 degrees, the researchers found, had lower BMIs than those who kept the heat lower. With the cost of energy so high, it's tempting to see money as the explanation: If people can afford to keep their homes so balmy, they could probably foot the bill for gym memberships, personal training, and fresh, healthy foods, too. But that didn't account for the difference in BMI, the researchers found.
Some earlier studies have shown that when people spend considerable time in chilly rooms – around 60 degrees – they burn fat and lose body mass, due to the activation of a specific type of fat called brown fat. (Yep, it's a fat that burns fat.) But most people don't keep their houses at 60, and if they do, they're likely to be bundled up, whereas people in the studies on the benefits of brown fat were wearing very little, since the whole point was to get chilly and rev up the brown fat. It's also possible that brown fat just doesn't burn off energy, or melt much fat, at the temperatures people usually live, says Michael Daly, a behavioral scientist at the University of Stirling in England, who led the study.
At higher than about 73 degrees, however, the body has to lose heat to maintain its temperature – and that requires energy, meaning it expends calories. At warmer temperatures, people also aren't as hungry, and they tend not to eat as much. "Coupled with decreased appetite and food intake, the additional energy expenditure associated with household temperatures of above [73 degrees] could lead to weight loss," says Daly.
So far, it's just an association that warmer homes mean lower BMIs, not proof that cranking up the heat to 73 will warm away those unwanted pounds. But it might be worth a try—especially since it sounds more pleasant than trying to shiver them off.