The Belly Burden
Forget the scale. New research points to waistline size as a better predictor of health
Perhaps one reason waists have grown so thick is that the majority of Americans do not realize that abdominal fat can be so hazardous. According to the Shape of the Nations report released by the World Heart Federation in September, 6 in 10 Americans did not rank abdominal fat as a leading risk factor for heart disease. And while a majority of doctors did know of the link between belly fat, heart disease, and diabetes, physicians measure waist circumferences of only 17 percent of their patients.
Yet, a study published in the British medical journal Lancet this month showed that among some 27,000 people in 52 countries, waist size as a ratio of hip circumference (the so-called waist-to-hip ratio) more accurately predicted which men and women would have heart attacks than did any other body measure, including weight and body mass index. "I don't think there is anything magic about this ratio, except that it's a window to the balance between muscle and fat," says Salim Yusuf, professor of medicine at Canada's McMaster University and lead author of the study. "Around the waist there is no large muscle." In other words, it's all excess fat.
High price. Little wonder, then, that a simple waist measurement, even in children, can accurately forecast who is likely to develop metabolic syndrome, a condition defined not only by waist size but also by having two or more additional health problems: high blood pressure, unhealthy cholesterol, high triglycerides, or insulin resistance. Metabolic syndrome significantly increases the risk of heart disease and leads to an early onset of type 2 diabetes.
Bigger waists also mean higher medical costs. Patients with 41-inch waists pay about $2,600 more per year in annual medical expenses than do those with 32-inch waists, according to a 2002 study in the journal Obesity Research. Larger waists can lead to more low-back pain, greater breathing difficulties, and persistent cough, compared with people with less abdominal fat. Waist size can even forecast who will have trouble bathing, dressing, and walking in old age. "Waist circumference is far more important than simply measuring how much someone weighs," says Lewis Kuller, an epidemiology professor at the University of Pittsburgh who has studied abdominal obesity and heart disease for decades.
Contrary to the notion that belly fat is a soft, inert tissue that nonchalantly sits on the waist, abdominal fat cells are actually little endocrine factories, producing hormones that send messages to many organs. "This central fat is the most metabolically active," says Manson. Belly fat appears to drain directly into the liver, she says, and as the fat breaks down, it releases substances that increase the body's resistance to insulin. "It seems to me that what has emerged is a sense that abdominal obesity promotes insulin resistance, which raises insulin levels, which increases appetite, which increases triglycerides, which causes the good HDL to go down, and increases sodium absorption, then blood volume expands, and blood pressure goes up," says William Kannel, a professor at Boston University Medical School and a former director of the Framingham Heart Study. Ultimately, this cascade of events leads to glucose intolerance, diabetes, hypertension, and accelerated development of coronary heart disease.
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