Brown Fat That Burns…Fat?

It sounds too good to be true, but scientists are looking into whether they can harness fat-burning brown fat for weight loss.

| March 6th, 2012
Fat That Burns…Fat?

What if fat weren’t the enemy after all and could actually help you lose weight?

Earlier this year, scientists at the Dana-Farber Cancer Institute published a study showing that injecting inactive mice with a natural hormone from muscle cells gives some of the benefits of exercise by turning regular fat into an energy-burning form of fat—without ever breaking a sweat.

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The potential for treating weight-related ailments, from diabetes to obesity, is enormous, and the scientists have already licensed their findings for drug development. 

According to the study, the hormone “causes a significant increase in total body energy expenditure and resistance to obesity-linked insulin resistance.” And it gives “some of the most important benefits of exercise and muscle activity.”

So does this mean that one day you can skip the gym altogether and just have an “exercise injection”?

The Skinny on Brown Fat

First, let’s take a look at what this energy-burning fat actually is. Fat, or adipose tissue, comes in two main types: white fat and brown fat. White fat is the most common. As the name suggests, this type of fat is white in color, due to its main component, triglycerides, which are also white. This fat forms globules and stores energy, which the body uses up during exercise or periods of fasting.

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White fat is what we generally talk about “losing” through diet and exercise, although we never actually lose fat cells through either of these actions. Instead, fat cells shrink when we lose weight and expand when we gain it.

Brown fat, on the other hand, differs from white fat in two ways. First, it doesn’t accumulate in energy-storing globules. Second, it is brown in color due to an overabundance of mitochondria, a structure that exists in nearly every cell in the body and turns food into energy through the production of adenosine triphosphate (ATP). But brown fat mitochondria work a little differently than the mitochondria in other cells. Instead of producing most of their energy as ATP, they make energy in the form of heat.

So what does all that mean? Essentially, white fat stores energy and brown fat burns it.

Scientists have known for decades that rodents and other mammals have brown fat, which likely evolved as a source of heat during hibernation. It’s also well known that human infants have a significant amount of brown fat, also likely to help keep them warm. But it wasn’t until 2009 that scientists discovered that small amounts of brown fat are still active in adult humans, mainly in the neck and along the collarbone and spine.

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Ever since the discovery of brown fat, scientists have tried to figure out how to use it for weight loss, notes George Bray, M.D., professor of medicine at the Pennington Biomedical Research Center at Louisiana Statue University, who was not involved in the research. “[Brown fat] has been around for quite awhile, and so far it hasn’t netted any therapeutic results,” he says. “But maybe this new finding will help do something that no one’s been able to do before.”

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