Hidden Fat Fact 2Body fat below the waist is not as dangerous.
Visceral fat is a threat for another reason: It's highly susceptible to inflammation.
"As the amount of stored fat increases, it triggers a cellular response designed to recruit immune cells," says Michael Schwartz, M.D., director of the diabetes and obesity center of excellence at the University of Washington. This leads to inflammation and can result in insulin resistance and a host of diseases associated with metabolic syndrome.
Fat below the waist behaves differently than visceral fat. "From an evolutionary standpoint, we believe that lower-body fat is intended as long-term storage. It's packed away, so it doesn't harm the rest of the body, and we use it as a last reserve," says Dr. Karpe.
According to a 2010 review conducted by Dr. Karpe, below-the-belt fat produces fewer inflammatory compounds, which means less cardiovascular damage. This gives women a health advantage because they tend to store more fat in their lower bodies than men do.
The fat women tend to carry on their hips? "That's one of the reasons we think women are more resistant to heart disease," Dr. Karpe says.
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Hidden Fat Fact 3Body fat is far more than a calorie storage tank.
Five or 10 years ago, researchers and physicians viewed fat merely as a storage system for energy—a soft balloon filled with calories. But they've since come to recognize it as an instrument that plays a critical role in your body's metabolic function. "Fat is the largest endocrine organ in the body," says David Piston, Ph.D., a professor of molecular physiology and biophysics at Vanderbilt University.
Even a 160-pound man with 13 percent body fat—that's a lean guy—has more than 20 pounds of fat. And that fat—or more specifically, the adipose cells that store fatty triglycerides and keep them out of the blood—is extremely important to his body's hormone regulation.
And that's just one of about 300 compounds coming from fat, says Dr. Karpe. Alas, not all of them are as benign as leptin. "When tissue is inflamed and overfilled with fat, it can pump out a lot of nasty stuff," he says.
That "stuff" can hijack your appetite, reprogram your fat-storage mechanisms, contribute to conditions like arthritis, and drive your triglyceride levels to deadly heights.
The best way to cut inflammation? Yep, pack some physical activity into each day. Researchers at Appalachian State University recently determined that highly fit people who reported frequently engaging in moderate exercise such as cycling, swimming, or jogging had nearly 50 percent less C-reactive protein, a marker for inflammation, in their blood than people who were unfit and rarely exercised.
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