Scientists Trick Mice's Fat Into Burning Calories; Weight Drops 20%

By Andrew Moseman | May 12, 2010 10:02 am

brownfatLast spring, researchers confirmed that brown fat—the kind that burns energy rather than storing it and is especially prevalent in newborns—can be found in small pockets in adults, too, and slimmer adults have more of it. This spring, a team says it might have found one of the first steps in activating that fat-burning fat in adults. Their study comes out in Science this week.

Brown fat is packed with energy-producing mitochondria, and babies have a lot of it because it helps them keep warm. Once humans begin to regulate their own body temperature they don’t need as much brown fat anymore, so it gets replaced by energy-storing white fat, which helps store energy but leads to expanded waistlines in this age of affluence.

Testing on mice, the team led by Stephan Herzig upped the use of an enzyme called cyclooxygenase-2 (COX-2). While the enzyme plays a role in many physiological functions, the researchers found that pushing it in mice could induce their white fat to act more like energy-burning brown fat, and their weight dropped by around 20 percent.

“There has been a lot of excitement around brown fat, but … there wasn’t any clear indication that turning up brown fat would make animals lose weight,” says Chad Cowan, a professor in the Department of Stem Cell and Regenerative Biology at Harvard Medical School who studies fat cell development. “What this paper does is make a good link to something that might be clinically beneficial [TIME].

Don’t get too excited just yet. This is a test on mice, not people, and there’s another problem: This transformation in the animals, white fat acting like brown fat, happened only when Herzig and his colleagues tricked the mice’s bodies into thinking they were at a colder temperature than they actually were:

That caveat is important because the COX-2 enzyme is present in a wide range of body tissues, and revving up its activity may lead to some serious side effects such as clotting problems, increased sensitivity to pain and even muscle abnormalities. Herzig found that manipulating the COX-2 pathway switched white fat to brown fat in the mice only when he simulated cold temperatures through metabolic tweaks — dilating small blood vessels and increasing the pumping of the heart — and made the rodents act as if they were shivering [TIME].

So Herzig’s team has only just started to figure out how humans might take advantage of our tiny brown fat deposits to battle our ever-growing white fat deposits. But, he says, if we find a way to do it that doesn’t involve the weird side effects, it might not take much brown fat to make a difference.

Scientists estimate that as little as 50 grams of brown adipose tissue in a normal adult human would be enough to increase energy consumption by 20 percent.”That’s not a lot of brown fat, but a big increase in energy burn,” said Herzig. “And this type of transplantation idea has been tried out with other types of animals and other types of cells, so in principle it works” [Reuters].

Related Content:
DISCOVER: The Fat That Can Make You Thin
DISCOVER: Killer Fat
80beats: A New Potential Weight-Loss Remedy: Fat-Burning Fat
80beats: “Baby Fat” In Adults Burns Regular Fat, May Help Prevent Diabetes

Image: Colorado State University

CATEGORIZED UNDER: Health & Medicine
MORE ABOUT: brown fat, mice, obesity
  • Mikey G

    I want some….

  • jumblepudding

    50 grams can make that much difference? Are we sure that more rotund people don’t have the same amount, just somehow buried under the white fat?

  • http://Discovery Andrew

    Great find. Would it be possible to remove brown fat from the body, clone/grow it in the lab, and re-introduce it back into the body?

  • thebarkleynow

    What’s the soonest something like this could go through clinical trials and show up in the marketplace? 2015?

  • Phrostbite

    I can’t help but think that, as health industries make so much money of people being ill, and the overweight (I’m overweight, also), are generally ill to a greater extent, that it pays to withold this kind of development…

    Heart disease is the biggest killer in the USA – therefore, it probably generates the biggest revenue for insurance and pharma. Why reduce the risk of heart disease, when you stand to profit by it.


  • http://discovermagazine Iain Park

    Instead of looking for a ‘silver bullet’, change your lifestyle folks, the only way to get fat is for calories in to exceed calories out. Period. No exceptions.

  • brentrobot

    How about a gene therapy that turns white fat into brown fat? You could really fine tune the process by having the treatments at quarterly intervals untill the patient was at the ideal weight.

  • Brian H

    I’ve been thin (can’t gain weight even when I’ve tried) and take in 2-3,000 Calories/day, sometimes more. I assume the excess just gets burned off as heat, sort of built-in “inefficiency” in the use of food. I don’t have really exceptional cold resistance, though I did grow up in a climate with severe winters.

    So without any effort my calories out always matches calories in.

  • caloriesburnerman

    All we need to do is stop eating too much, cut back on junk foods and concentrate on eating healthy and get off the computer and go out for a run!!!Fad diets and calorie counting is not always the answer. The Mediterranean diet and lifestyle is one of the best in the world; lots of fresh fruit and veg, fresh fish and meat and simple foods. Cheap processed food, some of which claim to be low in fat and calories are the worst – in the long term proving to cause heart disease. For some great diet recipes and tips on how to eat well by avoiding mass produced food check out our website:

    Do something about it!!!!!!!

  • raw food weightloss

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