Could brown fat cure obesity?

BY Cristen Conger / POSTED March 1, 2013
Hammerbrook - City can this really be true?
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No, this kind of brown fat certainly won't accelerate weight loss. (© David Brabyn/Corbis) No, this isn’t the kind of brown fat we’re talking about. (© David Brabyn/Corbis)

In my previous blog post on thermal dieting, I discussed how exposure to cold temperatures can potentially ramp up fat metabolism. In figuring out what makes this possible physiologically, scientists have pinpointed brown fat as the gatekeeper. Distinct from white fat, the stuff that gym memberships are made of, brown adipose tissue is chock-full of energy-chomping mitochondria (these iron-packed structures give the tissues its brown color, in fact) that kick into gear when the body’s internal temperature drops in order to generate heat. In short, when the mercury plummets, brown fat chows down on calories and fat cells. Rather cannibalistic, eh?

Babies are born with brown fat deposits to help keep them toasty, and rodents are rich in brown fat as well since their bodies don’t shiver when temperatures drop. Only recently, scientists also figured out that many adults retain pockets of brown fat in small quantities even as they age. Grownups don’t tote a lot of it around, though; a couple shot glasses-worth of the stuff is on the high end comparatively, as Wired’s Steven Leckhart reported. Even in those minimal doses, brown fat delivers a serious punch, tearing through around 80 more calories-per-hour  than a body normally would.

Now that brown fat’s presence is known in adults, scientists are furiously attempting to untangle how it can yield accelerated weight loss results in the face of rising obesity rates in the United States and abroad, keeping in mind that different people carry around different amounts of brown fat, along with the myriad variables associated with metabolism and weight loss.

To that end, some scientists have tried turning white fat brown. In 2010, a group of European scientists published a headline-generating study in which they were able to tinker with an enzyme in the white fat cells of mice and effectively convert it to brown fat. The results? A 20 percent drop in mouse weight. But the study authors also highlighted some not-so-fantastic possible impacts of rejiggering that COX-2 enzyme. TIME reported, “revving up its activity may lead to some serious side effects such as clotting problems, increased sensitivity to pain and even muscle abnormalities.”

Others are seeking to develop brown fat transplants, which have been shown to effectively spur weight loss and curb the risk of type 2 diabetes in mice. And there’s even a patriotic bent to this strand of research. The military has awarded a grant to a company developing “transferable brown fat cells,” Wired reports in hopes to trimming down troops.

And brown fat isn’t the only promising adipose tissue on the block. In 2012, researchers discovered another fat-burning fat they termed “beige fat,” which has similarly been hailed as a possible obesity remedy.

Whether these sepia-toned tissues can work their magic in humans remains to be seen, however. As diabetes and physiology professor Andre Carpentier cautioned WedMD in late 2012, additional brown fat still won’t be a substitute for overweight adults adjusting their daily health regimens. “You may end up burning a little bit more calories at the end of your day, but it’s not going to be anything close to what you can achieve by doing exercise and diet,” Carpentier said.

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