What Are Brown Fat Cells and Can They Help You Lose Weight?

The battle against stubborn layers of fat is something most of us struggle with daily. But what if one of the secrets to torching fat was held within the fat itself? Well, brown fat could be the key we are all looking for. But, what is brown fat? Isn’t all fat the same? And don’t you want to burn it all away to get a tight torso?

“Brown fat cells are literally brown in color because they contain an enormous amount of mitochondria, which are the power generators of cells,” says Sheila Collins, Ph.D., professor of the Integrative Metabolism Program at Sanford Burnham Prebys Medical Discovery Institute in Orlando, Florida. Within these mitochondria, brown fat cells burn fatty acids and glucose [sugar] and subsequently produce heat. So rather than store fat as white fat cells do, brown fat cells actually burn calories while producing heat.

Infants have a high amount of brown fat cells since they don’t have the ability to shiver yet, so these heat-producing cells help keep them warm. As the infant grows into childhood the amount of brown fat cells gradually declines since there isn’t a need for them since the child is now able to shiver to keep warm. Although brown fat cells continue to decline with age, a 2009 study found that most adults still have brown fat cells, albeit in small amounts — about 50 to 100 grams — and account for up to 20 percent of daily calorie burning.

“Brown fat evolved in warm-blooded animals in order to protect us from cold temperatures,” says Collins. “Remember, in caveman days we didn’t have houses or clothes, and even following the discovery of how to make fire, you still needed to stay warm enough to survive to live another day.”

How is Brown Fat Different Than White Fat?

Brown fat is different from our old enemy white fat in a few ways. White fat rings our bellies and pads our posteriors because it contains a special protein called an “uncoupling protein,” or UCP1, that allows the mitochondria to burn energy uncoupled from ATP production. “White fat cells do not possess the huge amounts of mitochondria or UCP1 because their goal is mainly to store calories for later energy requirements — like putting money in the bank for when you may need it down the road,” says Collins.

Evolutionarily speaking, this storage of fat is a good thing since it would help one survive during a famine. But, starvation is not the problem for most Americans. Ever since the Industrial Revolution (roughly 100 years ago), food has been packaged and available cheaply and in great quantities. This easy access to food has created a booming obesity epidemic linked to several chronic diseases.

“When white fat cells can no longer find room to continue to stock away these triglycerides [fats], this fat is put into places where it doesn’t belong — such as in the liver or skeletal muscle or the pancreas, where they wreak havoc by becoming toxic metabolites,” says Collins. “Avoiding this abnormal fat storage is critical for avoiding insulin resistance [which can lead to type 2 diabetes], cardiovascular disease, and risk of early death.”

Can we Harness the Calorie-burning Power of Brown Fat Cells?

Unfortunately, research has not yet proven a way for adults to lose measurable weight with brown fat cells. However, there is hope. A 2014 study — appropriately named the ICEMAN study — brown fat becomes more active in cold weather. The researchers found that chilly temps (about 66 degrees) may even make more brown fat cells grow. “The sensation of cold tells the brain to push the release of adrenaline to the brown fat cells to break down the triglycerides to fatty acids, to take up glucose, and to consume it to make heat,” says Collins.

Since cold temperature exposure is a trigger, Collins says “there is some interest in trying to slowly adapt people to cool temperatures daily to try to activate and sustain brown fat activity, like wearing a short-sleeved shirt instead of a long one, skipping putting on a sweater, or other simple strategies to keep your body cooler.” But, she mentions, it has to be a slow adaption because before you get to brown fat calorie burning, your body will first start using muscles to create heat by shivering, which is not a very comfortable fat-loss strategy.

Besides the cold, brown fat has also been found to be activated by stress. A small 2016 study in Experimental Physiology found that lean, healthy women subjected to stress had more brown fat activation then a period where they were just relaxing. The stressor was the anticipation of taking a test, which released the stress hormone cortisol and subsequently activated brown fat cells.

Hope For the Future

At this point, all we know from research is that the calorie-burning function of brown fat cells is activated by adrenaline from cold temperatures and cortisol from stress. And, feeling cold and stressed just to burn a negligible amount of calories is probably not one’s first choice among all the strategies to lose weight.

However, Collins hopes that future research will reveal more about the molecular triggers and pathways that promote brown fat cell activity so that researchers can utilize brown fat cells as an effective weight-loss tool. “We’d like to discover how to expand the numbers of these UCP1-containing brown fat cells and be able to keep them active at a modest pace,” says Collins. “These cells could possibly consume about 250 calories per day above our energy needs to maintain balance — after 365 days of elevated activity that would work out to about an extra 25 pounds of fat burned.” It seems promising, but research is not quite there yet.

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