Researchers demonstrated that temperature has a direct effect on the growth and loss of brown fat. Cool environments stimulate the growth of brown fat while warmer temperatures promote loss.
Brown fat burns energy, but researchers are unsure exactly how it relates to the human immune system, a Garvan Institute of Medical Research news release reported.
People with larger brown fat stores tend to be leaner and have lower blood sugar than those who do not. In the past the researchers have shown that white fat can be converted into brown fat.
To make their findings the researchers recruited five healthy men to spend at least 10 hours a day in a climate-controlled environment. For the first month the rooms were kept at a "thermo-neutral" temperature of 24 degrees Celsius; at this temperature body does not have to work to produce or lose heat. The temperature was moved down to 19 degrees for the second month, then back up to 24, and finally up to 27 degrees. At the end of each month the participants underwent a 'thermal metabolic evaluation."
The team found that brown fat increased during the cool month and decreased during times of higher temperatures.
"The big unknown until this study was whether or not we could actually manipulate brown fat to grow and shrink in a human being," Endocrinologist Dr Paul Lee from Sydney's Garvan Institute of Medical Research said in the news release.
"What we found was that the cold month increased brown fat by around [30 to 40 percent]. During the second thermo-neutral month at 24 degrees, the brown fat dropped back, returning to baseline. When we put the temperature up to 27 degrees during the fourth month, the volume of brown fat fell to below that of baseline," Lee said.
Brown fat could be a tool to help treat diabetics and help keep their blood sugar at a healthy level.
"The improvement in insulin sensitivity accompanying brown fat gain may open new avenues in the treatment of impaired glucose metabolism in the future. On the other hand, the reduction in mild cold exposure from widespread central heating in contemporary society may impair brown fat function and may be a hidden contributor to obesity and metabolic disorders," Lee said.
