The Hidden Dangers of Belly Fat

Where you carry those extra pounds can affect your risk of developing certain diseases.

By By Barbara Kantrowitz and Pat Wingert

May 23, 2006 - Sit down when you read this. Now, grab a hunk of flesh at your waist. If you're like many women, you've got a handful; nearly two thirds of American women are overweight or obese, according to the National Center for Health Statistics. While we all know that excess pounds increase your risk of certain diseases, you may not realize that where you carry the weight makes a big difference. Hefty hips and thighs (a pear-shaped body) may cause you some dismay when you look in the mirror, but researchers have found that abdominal fat (an apple shape) could be even more hazardous to your health.

To understand why, you need to know a little bit about the different kinds of fat in your body. Most of your fat cells are under your skin-in your hips, arms or thighs (you know what we're talking about). That's called subcutaneous fat, and it's what you're able to grab in your hand. You have some subcutaneous fat in your stomach, as well, but the fat that concerns researchers is called visceral fat. It surrounds organs in the abdominal area and it's part of the omentum, a drape of tissue that hangs down from the intestines. You can't touch it or feel it. In the average person, about 10 percent of total body fat is visceral while 90 percent is subcutaneous. In a very obese person, that ratio changes to about 25:75.

Scientists have found that there's a correlation between visceral fat and various metabolic diseases (like diabetes) that put you at risk for cardiovascular problems. In fact, the evidence against visceral fat is so strong that scientists say measuring your waist circumference may be a better indicator than your BMI (or body mass index, a ratio of weight to height) of your risk of disease. For women, a waist size of more than 35 inches signals potential trouble; in men, it's 40 inches.

Is there something about how visceral fat functions in the body that makes it more dangerous than subcutaneous fat? Researchers aren't sure, says Samuel Klein, director of the Center for Human Nutrition at Washington University Medical School in St. Louis. When scientists look at visceral fat cells out of the body, they appear to be more active than subcutaneous fat cells. "Whether that's true in humans or animals when they are alive isn't clear," Klein says. Studying visceral fat cells inside the body is difficult, Klein says, because you would need access to the portal vein, which drains visceral fat-and that would mean inserting some kind of tube into the body.

Klein and his colleagues have studied what happens when they sucked out subcutaneous abdominal fat by liposuction. In a study published in the New England Journal of Medicine in 2004, they looked at 15 obese women with excessive belly fat before abdominal liposuction and 10 to 12 weeks after surgery. Although they removed large amounts of fat (about 20 percent of the patients' total body mass), there were no health benefits-no changes in cholesterol, blood pressure or other risk factors for heart disease. "Removing the fat alone is not enough," Klein says. "How you remove it is important." In other words, you have to eat less and exercise more.

Now that we've gotten you all depressed just as swimsuit season starts, we'll give you the good news. Although your genes do play a major role in determining where your body stores subcutaneous fat, researchers have found that both your level of physical activity and what you eat can affect the amount of visceral fat you have. People who eat polyunsaturated fats instead of saturated fats have less visceral fat. Exercising daily also helps prevent the accumulation of visceral fat. And when you start to lose weight, you lose visceral fat quickly. In some studies, people who lost only 10 to 15 percent of their total body weight through diet and exercise lost 30 percent of their visceral fat and saw significant improvement in markers of disease risk, like cholesterol and blood pressure (the benefits not achieved by liposuction).

That's an important message at any age, but it's increasingly critical as you get older since age also raises your risk of heart disease. "Obesity in the elderly is a major problem," says Klein. "It has become a major source of disability and nursing-home admissions. The weight you carry when you're 50 is no longer tolerable when you're 80." After menopause, women start accumulating fat in the places where men do (think beer belly), which means more visceral fat as well. So start losing now by eating healthier food and cutting portion size. Make sure you get regular physical activity-at least half an hour a day. And watch your waistline melt away.