Does Raising the Thermostat Increase Obesity?
Study Suggests Link Between Keeping Warm and the Obesity Epidemic
By Denise Mann
WebMD Health News
Reviewed by Laura J. Martin, MD
close up of hand turning up heat

Jan. 25, 2011 -- Baby, it’s cold outside, but keeping warm by cranking up the heat may play a role -- albeit not a very big one -- in the current obesity epidemic, a new study suggests.

"Changes in the way we eat and physical activity levels are the primary factors behind increases in obesity, [but] other aspects of our lifestyle can also make a contribution," says study researcher Fiona Johnson, a research psychologist in the department of epidemiology and public Health at University College London.

Johnson and colleagues reviewed the literature to determine how our desire to stay warm may be affecting our body weight.

The study is published in Obesity Reviews.

Our bodies must work to stay warm when it’s cold, which means we expend more energy or calories. "Our love of warmth may be reducing our expenditure and contributing to the obesity 'epidemic,'" she tells WebMD in an email. "The less time spent in the cold means less time when the body is burning energy to stay warm."

But there is more to it. "It is also likely that a lack of exposure to cold reduces our capacity to generate heat, by diminishing brown fat stores," she says.
Brown Fat Cools Obesity

Until somewhat recently, researchers thought that only babies had substantial brown fat to help keep warm, and that brown fat went away over time. New research is showing that adults have brown fat, too. Brown fat generates body heat and becomes activated when you're cold. 

"While white fat acts as an energy storage tissue, brown fat could be viewed as the body's furnace -- burning energy to create heat," she says. “Regular exposure to cold appears to slow down the rate of loss and will and stimulate the development of new brown fat cells."

Going forward, Johnson says, “We would like to see studies that directly measure the effects of cold exposure on brown fat stores, energy balance and body weight by studying the changes that go on in the body when the thermal environment changes."
Turning Down the Thermostat

As far as what someone can do today, Johnson says: “I think it is too early to say exactly what changes to your lifestyle will contribute to increasing energy expenditure, but for now turning down the thermostat at home is unlikely to cause any harm and also contributes to lowering the household energy consumption.”

In the future, she says, “Some form of cold exposure could become an obesity treatment in itself, or that other ways to stimulate the development of brown fat in the body might be established which will boost the capacity for energy expenditure.”

 “When you look at what could be causing the obesity epidemic, there are many possible causes besides eating too much and not exercising enough, and this is clearly one of them,” says Louis Aronne, MD, founder and director of the Comprehensive Weight Control Program at New York-Presbyterian Hospital/Weill Cornell Medical Center in New York.