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Why Not All Fat is Created Equal

Apr 22, 2008

The recent report that having a pot belly in your 40s roughly triples your risk of dementia in later life is just the tip of an ominous adipose iceberg.

Belly fat – the visceral kind that accumulates around internal organs – has also been linked to diabetes, high blood pressure, stroke, heart disease, gallbladder disease, sleep apnea and numerous cancers.

Having a big belly is even more closely correlated with health problems than obesity in general. Last week, researchers from Harvard Medical School reported that in a study of 44,636 women, those with waists larger than 35 inches were 79 percent more likely to die prematurely than those with waists less than 27 inches, even if their weight was normal.
Rudolph L. Leibel, co-director of the Naomi Berrie Diabetes Center at Columbia University Medical Center in New York states that for men, the danger point seems to be 40 inches or more. "These guys with small behinds but big ‘beer guts’ are at greater risk for health problems than men with higher Body Mass Index, but relatively less fat in the abdominal region." 
What makes abdominal fat so sinister isn’t completely understood. One body of research suggests that visceral fat may make metabolic mischief in its own right, promoting insulin resistance, a precursor to diabetes, and inflammation, which may lead to heart disease.

Dr. Leibel, who notes that if fat is building up inside the belly, it’s probably also collecting in the liver, where it can lead to cirrhosis. Another theory suggests that a big gut is essentially a marker – an all-too-visible sign of psychological stress and other health problems, since the stress hormone cortisol seems to send fat into the abdomen. "It’s possible it’s a semi-innocent bystander, like a canary in the coal mine."

The connection with dementia is also not well-understood; it could be that belly fat is linked to high blood pressure and poor vascular function, which then leads to Alzheimer’s disease; or it could be a more random association, like gray hair going hand in hand with heart disease.

Experts now think that subcutaneous fat – the flabby variety under the skin in areas like the buttocks, legs and arms – while unfashionable, is fairly benign. Researchers at the Washington University School of Medicine in St. Louis demonstrated that when they removed an average of 22 pounds of subcutaneous fat via liposuction from 15 overweight women, they found no change in the women’s cholesterol levels, triglycerides, insulin sensitivity or other health risks. "If they had lost that much fat by dieting, they would have substantially improved their metabolic profile, but they didn’t," says Samuel Klein, the study’s principal investigator.

Of course, people generally can’t choose where their fat is stored. That’s determined mostly by heredity, hormones and aging. Men tend to deposit more fat in the gut than women, though after menopause, women start accumulating fat in the abdomen, too.

The good news for both sexes is that visceral fat is often the first to go when someone loses weight in general. Aerobic exercise, like walking or running, is particularly effective. Doing sit-ups, abdominal crunches and pilates can strengthen your abdominal muscles, and help hold your stomach in, but they won’t target visceral fat specifically.

"I’ve seen guys at the gym with impressive six-pack abs, but their gut is sticking out," says Michael D. Jensen, an endocrinologist at the Mayo Clinic in Rochester, Minn. "The minute they stop working out four hours a day, they’ll be in big trouble."

Surgically removing visceral fat has been done on animals and some humans experimentally, but it is far more difficult and isn’t likely to be a weight-loss option anytime soon.

Reducing stress may be helpful. But supplements that promise to flatten your belly by reducing cortisol could be harmful, some experts warn. "Your adrenal gland is like a power tool," Dr. Leibel says. "You don’t want to be messing around in the garage with it without supervision."