Why That Beer Belly is a Killer
About 300,000 people die every year in the United States because they are obese. And with the population getting fatter and fatter, that number is expected to swell, perhaps even surpassing the 400,000 deaths each year caused by smoking.
But is fat really fatal? Or do fat people just lead unhealthy lives that make them more likely to fall ill? It's been clear for years that obese people are more apt to suffer from heart disease, stroke, diabetes, and a variety of cancers. What's less clear is whether fatty tissue is involved in these illnesses. That's no small question: Heart disease and cancer together account for more than half of all deaths each year in the United States, and 17 million Americans have Type II diabetes.
Mounting evidence now suggests that fat really is a culprit. Rather than lying inert in beer belly and thigh, body fat appears to be an active organ, pumping out powerful hormones and immune-system messengers that affect the cardiovascular system, liver, pancreas, and brain. "Fat cells are hard at work, and they are dynamic," says Allen Spiegel, director of the National Institute of Diabetes and Digestive and Kidney Diseases.
Over the past decade, researchers have gained a much better understanding of how fat acts within the body, discovering fat-generated hormones like leptin that appear to play a major role in regulating the body's energy balance. Proteins that prompt inflammation are also produced by fat cells. Scientists are intensely interested in that process, because they increasingly suspect that similar mechanisms of inflammation are involved in causing cardiovascular disease, stroke, and diabetes. Fat cells also secrete the sex hormone estrogen, which may contribute to obese women's greater likelihood for postmenopausal breast cancer.
But not all body fat is alike. Fat packed around the abdominal organs is more metabolically active than fat on the derriere. Abdominal fat is also a key indicator of "metabolic syndrome," a group of risk factors, including high blood pressure, insulin resistance, low "good" HDL cholesterol, and elevated inflammatory proteins, that predispose people to diabetes and cardiovascular disease. An estimated 20 to 25 percent of Americans have metabolic syndrome. It also appears that, as a person gains weight, the number, size, location, and even function of fat cells may change. The plumped-up fat cells differ in their metabolism and the hormones they secrete, further altering the body's chemistry. It's such discoveries that have scientists delving deeper and deeper into fat's biological complexity.
Fat's Sinister Agenda
Scientists now think that body fat produces hormones that affect major organs and contribute to disease.
Cardiovascular disease. One's risk of heart disease and stroke rises after gaining as few as 10 pounds. High blood pressure, the leading risk factor for stroke, is twice as common in obese adults.
Type II Diabetes. Gaining 11 to 18 pounds doubles a person's risk of developing Type II diabetes.
Cancer. Women who gain more than 20 pounds after age 18 double their risk of postmenopausal breast cancer. The risk of colon, endometrial, kidney, and gallbladder cancer also rises with weight gain.
[Drawing labels]
Stroke; Breast cancer; Heart disease; Diabetes; Abdominal fat
Rod Little--USN&WR
-Nancy Shute
This story appears in the February 9, 2004 print edition of U.S. News & World Report.