Study says staying cool creates 'good' brown fat

The study was led by endocrinologist Dr. Paul Lee from Sydney's Garvan Institute of Medical Research, whose past research has indicated brown fat, prevalent in lean people, is the key player in metabolism because it generates heat.

"Excitement in the brown fat field has risen significantly over last few years because its energy-burning nature makes it a potential therapeutic target against obesity and diabetes," said Dr. Lee about his prior study, published in Cell Metabolism, indicating that shivering and exercise may convert white fat to brown.

The new study, The Impact of Chronic Cold Exposure in Humans (ICEMAN) study at the National Institutes of Health (NIH) in Washington DC, worked with five healthy men over a four-month period.

For the duration of the study, they lived in climate-controlled rooms of various temperatures at the NIH Clinical Center in Washington DC, although they maintained normal routines during the day.

At the end of each month, researchers conducted "thermal metabolic evaluations" of participants.

In addition to biopsies of muscle and fat, they performed cold-stimulated CT scans to measure the amount of brown fat in the body, which proliferated during the cool month during which participants lived for a minimum of 10 hours in an environment of 19 degrees C (66F).

During the first month, researchers set their subjects' rooms to 24 degrees C (75F), the next month to 19C, back to 24C for the third month and to 27 degrees C (80F) the fourth and final month.

The body does not need to work to produce heat in 24C, considered a "thermo-neutral" temperature in scientific terms, so analysis conducted at the end of the first and last months in which participants lived at this temperature represented the baseline.

"The big unknown until this study was whether or not we could actually manipulate brown fat to grow and shrink in a human being," said Dr Lee. "What we found was that the cold month increased brown fat by around 30-40%."

Dr. Lee's findings indicate that not turning up the thermostat during winter months could play a role in fighting obesity.

"During the second thermo-neutral month at 24 degrees, the brown fat dropped back, returning to baseline," says Lee.

His research supports another recent study exploring the effects of ambient temperature on health and weight management. The Dutch study, published in the journal Science & Society, indicates that frequent, prologned exposure to mild cold mobilizes brown fat, provoking calorie burning up to five times the average resting metabolic rate.

Dr. Lee's study indicates that cold actually creates the cells instead of merely activating their heat-generating capabilities.