— -- Turning down the thermostat may not only help you save on your heating bill, it also could be the secret to losing weight.
Research published last year in the journal Cell Metabolism compared the calorie burn in subjects as they exercised in a 65 degree lab and then lay down on a bed chilled to 53 degrees until they started shivering.
In both tests, the subjects produced a hormone called irisin that converted sluggish white fat cells designed to store body fat into metabolically active brown fat cells designed to rev up calorie burn. Shivering muscles released another hormone, FGF21, that further boosted calorie burn.
Around 50 grams of brown fat burned an additional 300 calories daily, the study found. That’s about the same as a 30-minute jog, according the Compendium of Physical Activity.
“This is most likely not a permanent change but it can produce some weight loss,” said Ajay Chawla, a brown fat researcher with the University of California, San Francisco who was not involved with the study.
Babies are born with vast amounts of brown fat distributed over their bodies that melts away as they grow, Chawla said. In response to cold, adults may make another kind of brown fat, known as “beige brown fat,” that has been shown to reverse obesity in mice.
“Most of us are not under much thermal stress, which means brown fat production has basically been turned off in our bodies,” he said.
Using the cold to lose weight without exercise is theoretically possible by ratcheting down the thermostat to the point where you feel chilly all the time, Chawla said.
A Japanese study published last year showed subjects who donned hospital gowns and spent several hours a day in a 61-degree room lost about a pound in six weeks. Keep up this routine over the course of the year and you would expect to drop about 15 pounds without setting foot in the gym, Chawla said.
However, as Chawla pointed out, most people have little tolerance for such discomfort. They’d prefer to stay toasty warm.
“Enduring a few moments of cold each day in the winter isn’t enough to stimulate brown fat production,” Chawla said. “People may actually gain weight in colder months because they tend to move less and eat more.”
The solution, Chawla said, may eventually come in the form of a pill.
“Pharmacologically, we may be able to develop something that stimulates brown fat cells without the exposure to cold,” he said.