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There's a Type of Fat That Babies Have… Here's why you need it, too

George King, MD
Harvard Medical School

Fight fat at all costs! For decades, this has been the prevailing message from medical experts. But cutting-edge research suggests that you actually can benefit from having more fat–as long as it's the right kind of fat.

What's new: Scientists have discovered that many adults have small amounts of brown fat. Brown fat is more active than any other tissue in the body. In fact, when fully activated, brown fat generates 300 times more heat than any other tissue in the body.

A few ounces of this high-octane fat can burn as much as 200 to 300 calories a day, the equivalent of 30 minutes of brisk walking.

Pure Energy

Most of us think of "fat" as the white stuff that stores calories and tends to accumulate, pound after unwelcome pound, on the belly, thighs and hips. White fat has caused the nation's obesity epidemic along with the attendant risks, including higher rates of medical problems such as heart disease, diabetes and cancer.

Brown fat does the opposite. It doesn't store calories– it burns them at a very rapid rate, thus boosting weight loss. It also improves insulin sensitivity and prevents excess glucose (blood sugar) accumulation in the blood.

A New Discovery

Until recently, brown fat was thought to exist only in newborns and babies. They have small amounts of brown fat between their shoulder blades–this fat generates heat and protects them from cold.

MRIs and other imaging tests now have revealed that some people retain brown fat–along with an "intermediary" form known as beige fat–throughout their lives. In adults, it's located around the neck, in between the collarbone and shoulder, and in parts of the spine.

People with generous amounts of brown fat tend to be leaner than those without it.

It's clear that brown fat is beneficial. The million-dollar question is whether it can be manipulated either by increasing the amount in one's body or making it more metabolically active –to prevent diabetes, improve glucose control and help with weight loss. The preliminary answer seems to be yes. Research has shown that it may be possible to transform white fat into the beneficial brown and beige forms and to make them burn even more calories and regulate blood sugar more efficiently.

Cold is the Key

Since brown fat is meant to keep infants warm, it makes sense that it would be more active at cold temperatures.

New Study: For four months, researchers exposed men to different temperatures–one temperature for and entire month. Participants went about their normal lives during the day but slept in temperature-controlled rooms at night. After one month of sleeping in 660 F temperatures, the men's stores of brown fat almost doubled. They burned more calories and had improvements in insulin sensitivity. When the heat was turned up (to 810 F), their brown fat diminished.

In another study, researchers found that sitting in a 590 F room for two hours wearing summer clothing stimulated brown fat to burn an extra 100 to 250 calories, depending on the individual.

Light the Fire

Here's what you can do to increase and activate brown fat…

Keep it Cold. Lowering the thermostat of your home to the mid- 60s or below may be enough to stimulate at least some brown-fat activity. That's chillier than the temperature at which most people keep their homes, but it's easy to get use to.

Bonus: Cool temperatures also my overcome the set-point phenomenon, the discouraging tendency of the body to slow down and burn fewer calories when you're dieting.

Dress Lightly. During the cold months, go outside a few times a day while wearing only the basics–a sweater, a light jacket or even just a T-shirt. Any exposure to cold will help you burn more calories. A study in northern Finland found that people who worked outdoors had more brown fat than those who worked inside.

Alternative: Cooling vests, which use cold water or refrigeration to lower body temperature, are available on line. Exposing even small parts of the body to cold—with a cooling band wrapped around and arm or a leg, for example—activates brown fat.

Regular workouts.

In addition to the obvious benefits–better cardiovascular health, improved blood sugar weight loss, etc…–exercise causes an increase in irisin, a hormone that appears to convert white fat into the beige form. Beige fat isn't quite as active as brown fat, but it still has a high metabolic rate.

I advise patients to get a mix of aerobic and strength-training workouts, preferably for 30 to 45 minutes, most days of the week.

Forget hot yoga

It makes no sense to exercise in a hot room. People think that the extra perspiration is a sign of weight loss. It's not–and a hot environment inhibits brown-fat activity.

Bottom Line/Personal interview with George King, MD, professor of medicine at Harvard Medical School, Boston, MA. October 1, 2014