Australian researchers behind a new study found that cooler indoor temperatures stimulate the growth of healthy brown fat, while warm temperatures cause the loss of this beneficial type of fat.
Brown fat, also known as brown adipose tissue (BAT), is a special kind of fat that burns energy to generate heat.
The study results, published in the journal Diabetes, show how this good fat may have some metabolic advantages.
Lead author and endocrinologist Dr. Paul Lee has shown in previous studies that people with plentiful brown fat stores tend to be lean and have low blood sugar levels.
This ICEMAN study, standing for The Impact of Chronic Cold Exposure in Humans, involved five healthy men exposed to different room temperatures over a four-month period: 75 degrees Fahrenheit during the first month, 66 degrees during the second month, back to 75 degrees during the third month, and 80.5 degrees during the fourth month.
After going about their day normally, they would return to these temperature-regulated rooms at night and spend 10 hours there.
Cold-stimulated PET/CT scans found that brown fat increased during the cool month and fell during the warm month.
"So in addition to unhealthy diet and physical inactivity, it is tempting to speculate that the subtle shift in temperature exposure could be a contributing factor to the rise in obesity," Lee pointed out in a news release.
They also found that the men's insulin sensitivity increased when they had greater amounts of brown fat, meaning they required less insulin after a meal to bring their blood sugar levels down.
"The improvement in insulin sensitivity accompanying brown fat gain may open new avenues in the treatment of impaired glucose metabolism in the future," Lee explained.
"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."