A new paper in Trends in Endocrinology & Metabolism finds that regular exposure to mild cold may be a healthy and sustainable way to help people lose weight. Obviously so would eating less.
Their work suggests our warm and cozy homes and offices might be partly responsible for our expanding waistlines rather than our buffet lunches.
The researchers started studying the effects of mild cold about 10 years ago. Earlier studies of temperature primarily focused on the extreme for application to the military, firefighters, and others. But studies began to find differences amongst people in their response to mild cold conditions. That led researchers to an important discovery: heat-generating, calorie-burning brown fat isn't just for babies. Adults have it too and some more than others.
The authors say they now have evidence to suggest that a more variable indoor temperature – one that is allowed to drift along with temperatures outside – might be beneficial, although long-term effects still await further investigation. A research group from Japan found a decrease in body fat after people spent 2 hours per day at 17 degrees Celsius (62.6 degrees F) for six weeks.
They also found that people get used to the cold over time. After six hours a day in the cold for a period of 10 days, people in their study increased brown fat, felt more comfortable and shivered less at 15 degree Celsius (59 degrees F).
"Since most of us are exposed to indoor conditions 90 percent of the time, it is worth exploring health aspects of ambient temperatures," said first author of the article Wouter van Marken Lichtenbelt of Maastricht University Medical Center in The Netherlands. "What would it mean if we let our bodies work again to control body temperature? We hypothesize that the thermal environment affects human health and more specifically that frequent mild cold exposure can significantly affect our energy expenditure over sustained time periods."
In young and middle-aged people at least, non-shivering heat production can account for a few percent up to 30 percent of the body's energy budget, they say. That means lower temperatures can significantly affect the amount of energy a person expends overall.
So perhaps, in addition to our exercise training, we need to train ourselves to spend more time in the cold. Managing that in practice might take some convincing, however.
"Indoor temperature in most buildings is regulated to minimize the percentage of people dissatisfied," the researchers write. "This results in relatively high indoor temperatures in wintertime. This is evident in offices, in dwellings and is most pronounced in care centers and hospitals. By lack of exposure to a varied ambient temperature, whole populations may be prone to develop diseases like obesity. In addition, people become vulnerable to sudden changes in ambient temperature."