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.
While diet and exercise clearly contribute to changes in body weight, there are other factors that contribute to obesity including the theory advanced in this new report, he says.
“There is no question that there is less variability in the temperature where we spend most of our time, and this paper explores in more detail some of the aspects of thermogenics or heat making that occur in the cold,” he explains. “You may lose some of these natural weight-gain blunting abilities when in a temperature-neutral environment most of the time.”
There is no proven way to capitalize on this phenomenon.
“Putting ice around your shoulders will be uncomfortable and there is no evidence that it will help burn fat or lose weight,” he says.
“There is merit in this thought process,” says Mitchell Roslin, MD, chief of obesity surgery at Lenox Hill Hospital in New York, of the new study.
“If I put you out in the cold, you have to burn enough energy to keep your body temperature at 98.6 F to stay relatively warm,” he says. “That is why we are considered warm-blooded.”
The colder it is, the more the body has to come up with sources to keep this going, he explains.
“This is an adaptive mechanism that we have lost because we are not out in the chronic cold anymore,” he says.
Roslin suggests keeping your house temperature under 70 degrees and spending more time being active outdoors to help more efficiently burn calories.
Scott Kahan, MD, co-director of the George Washington University Weight Management Program in Washington, D.C., points out that this phenomenon, while interesting, plays only a “minor contributing role in the obesity epidemic.”
It may help researchers better understand a role for brown fat in weight regulation and highlight ways to manipulate or activate brown fat stores in the future, he says.
“We are essentially all gaining weight, and largely this is due to environmental changes,” he says. "We need to address the ‘obesogenic’ environment that our society has become and help people learn to better navigate these environments.”
This new study in no way, shape, or form suggests that cooling will combat obesity, he says.