We’re used to thinking of body fat as bad. But for scientists, fat holds the key to some interesting clues about weight and body shape — specifically, brown fat.
What we know about the white kind of fat is that it stores excess calories so the body can access it when hungry, and it releases hormones that help control metabolism.
But brown fat, which was once thought to be gone from the body by the time we reached adolescence, has scientists buzzing. Not only do adults have brown fat, but lean people have more of it than overweight people. When it’s stimulated, it can burn calories.
The buzz centers on harnessing brown fat for calorie burning to eliminate obesity.
What is brown fat?
Brown fat, also known as brown adipose tissue, is a special kind of fat that burns energy and glucose to generate heat. It keeps small animals and babies warm, and animals with abundant brown fat are protected from diabetes and obesity.
“Brown fat is a small amount of fat, typically around the neck area, that makes up 1% of the fat the body has,” says weight-loss specialist Dr. Peter Vash, assistant clinical professor of medicine at the Center for Health Sciences at UCLA. “It's metabolically much more active. Brown fat burns calories to create heat. It’s found around the neck area to help heat up the blood vessels and arteries taking blood to the brain. Babies are born with much more brown fat, but the percentage decreases with age.”
When you're exposed to cold, your body makes more brown fat. That helps to keep you warm in winter.
But brown fat doesn't just generate heat and keep your body warm.
Research finds that brown fat may also protect against obesity and Type 2 diabetes. A study, published in the journal Nature, suggests that brown fat can help filter excessive amino acids that can increase the risk of those health concerns. The findings may help lead to new treatments.
How brown fat works with metabolism
Dr. Paul Lee, a former research fellow at the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health, said the regulation of brown fat and its relationship to metabolism in humans are still unclear.
Research shows that brown fat may be manipulated by ambient temperature. In one study, mild cold exposure stimulated brown fat activity while mild warm exposure suppressed it. Brown fat increase was accompanied by improvement in insulin sensitivity and energy burning rate after food, Lee explains.
In the study, five men between ages 19 and 23 were tracked for four months. The volunteers engaged in usual daytime activities but slept in a private room in which the air temperature varied monthly between 66 and 81 degree F. Temperature detectors monitored each volunteer's exposed temperature, and at the end of each month the researchers measured the men's brown fat and energy metabolism and found that mild cold increased the men's brown fat.
Although promising, sleeping in cool temperatures or sitting in an ice bath nightly is not a realistic approach to weight loss, Vash says.
“Yes, your body will stimulate brown fat in an attempt to keep the blood going to the brain heated (this is essentially what your body is doing when you shiver) but this is not an effective way to lose weight long-term,” he says. “A 20-minute ice bath is only about a 50-calorie burn, at most.”
If you can convert white fat (shown above right) to brown fat (on the left), you essentially change a storage area into a burning furnace.
“However, we don’t yet have a practical way to convert white fat into brown fat. There is the potential of a drug or treatment in the future that will assist in converting white fat into brown fat to help people lose weight,” Vash says. “The process of stimulating brown fat effectively and therapeutically has yet to be discovered.”
The future of brown fat
Scientists are shooting for a drug that could increase brown fat. But it won’t be a miracle pill. You’ll still need to combine it with a healthful diet and exercise to actually burn that fat.
“A more realistic approach to losing weight is encouraging people to eat less food, drink less alcohol and exercise more,” Vash says. This is a much more effective way to lose weight — at least until a medical approach to converting white fat to brown becomes available.
Until a fat pill is invented, scientists speculate about ways to rev up brown fat burning such as lowering your home thermostat in cool weather and spending time outdoors in the cold. Studies show that people who work outdoors have higher brown fat activity than average, so why not take advantage and spend some time chilling? Maybe it could boost your brown fat while you wait for science to catch up.
Editor's note: This story has been updated with new information since it was published in November 2014.