"Up until a few years ago, we didn't think it did very much in adults," said Dr. Jana Klauer, a physician in private practice in New York.
Klauer said small animals and babies have brown adipose tissue, but as people get older, they tend to lose it. Studies have shown, however, that some adults do have it, though it hasn't been determined how common it is.
Klauer and Eckel cited a recent study done in Japan that exposed two groups of men to cold. One group had brown adipose tissue and the other didn't.
"They found that in people that had the brown fat, energy expenditure went up 400 more calories per day when they were exposed to cold," said Klauer. "They were using 400 more calories to generate heat."
The results suggest that weight loss in cold temperatures may be easier for people with brown adipose tissue.
"It's not going to make a difference whether you're exposed to cold or a neutral temperature if you don't have any brown adipose tissue," said Klauer.
It's not easy to determine whether a person has this type of tissue. It involves injecting fructose into the body, which then is taken up by the brown adipose tissue.
Interesting Findings, But More Research Needed
Experts say the findings are interesting and could lead to a whole new area of obesity research.
"One obvious experiment is to see what happens when temperatures in obesity-prone populations are lowered," said Eckel.
"Establishing the significance and magnitude of the effects of both short-term and long-term thermal exposures on body weight could lead to the development of novel therapies to address obesity on an individual and a population level," the authors wrote.
McCullough said many doctors are telling patients to turn down the thermostat to help lose weight, but Klauer said it's way too soon to send the message that the cold weather can have an impact.
"People shouldn't take away that they'll lose weight if they don't wear a jacket," she said.