How Fat Can Fuel Weight Loss

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How Fat Can Fuel Weight Loss

Did you know that there is a kind of fat that can actually help you lose weight? It’s called brown fat, and we have been aware of it for years -- but, until just recently, scientists believed that it was only found in babies, small mammals and hibernating animals. The big news is that adult humans have brown fat as well, so scientists are working furiously to figure out how to put it to work. If this research continues along its promising path, it may someday also be used as a mechanism to help people lose weight.

BROWN FAT BURNS LOTS OF CALORIES

Curiously, the discovery that adults have brown fat came about because PET (Positron Emission Tomography) scans of the neck area were sometimes blocked by a mysterious gleaming tissue beneath the subcutaneous fat, which turned out to be brown fat. When I spoke with M. Cypess, MD, PhD, who led the brown fat study at Joslin Diabetes Center (Boston), he told me that scientists had assumed adults didn’t have brown fat because there is none between their shoulder blades, which is where babies carry most of theirs. As it turns out, adult brown fat is found primarily in the front of the neck and around the collar bone, but Dr. Cypess told me that researchers believe we probably carry it in other areas of the body as well.

Even babies have only a bit of brown fat (just 1% of their total body weight) and adults certainly have far less... but, as it happens, even small amounts can make a big difference. A mere two ounces can burn 300 to 500 calories per day. Furthermore, while brown fat gets some of its fuel from glucose, it also leeches it away from white fat. So it’s not a huge step to theorize that increasing the amount of brown fat in the body could lead to decreased stores of white fat -- in other words, significant weight loss. This has been achieved already in the mouse world, in fact... but things get a little more complicated when it comes to human beings.

ACTIVATING BROWN FAT Brown fat burns calories when it is activated, which normally is done by cold -- and bundling up against the cold inactivates it. Not surprisingly, obese people have less brown fat than do lean people, possibly because their excess fat insulates against the cold, says Dr. Cypess. Brown fat also decreases with age, for reasons unknown, which may be one reason it is harder to lose weight as we get older.

Unfortunately, all the ways that we currently know to activate this energy-expenditure process (called thermogenesis) in amounts sufficient for weight loss are problematic. Nicotine is one, for instance (although Dr. Cypess says this is not the reason why smokers are often thin), but we know that’s not good for us. Then there is the stimulant ephedra, which as you may recall was once a principal ingredient in over-the-counter weight-loss drugs until it proved to cause a variety of problems from anxiety to heart attack. The other known activator is norepinephrine, the stress hormone that triggers the flight-or-fight response in the body, which also has undesirable effects.

FUTURE RESEARCH Challenges aside, I think we can expect to hear lots more about brown fat in the future as scientists and manufacturers continue to search for the holy grail of weight loss. Its discovery in adults is just the first step, says Dr. Cypess -- researchers are working to learn its role in the adult body, with a focus on finding out how to increase levels as well as how to "selectively" turn on the brown fat function. Finding those answers could mean that future struggles to lose weight would become much easier for all.

Source(s): M. Cypess, MD, PhD, Joslin Diabetes Center, Boston.

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