Does your belt need a new hole--or three? Has that "spare tire" made it hard to tie your shoes? And what's happened to clothing sizes? Why has everything become just too darn tight around the waist? If you find yourself asking these questions while you lie down on the bed, hold your breath, and try to get that zipper all the way up, join the club. Americans' collective waistline is expanding--a lot. And medical researchers are beginning to understand the complex physiology behind a simple truth women have believed for centuries: the smaller the waist, the better the life.
Over the past 10 years, a raft of new studies have shown that predicting a person's long-term health may be as simple as taking a waist measurement. Fat around the waist has been linked to a greater risk of heart disease, diabetes, stroke, hypertension, breathing problems, disability, some cancers, and higher mortality rates. The medical community once believed that it was weight itself or the body mass index that led to serious illness and earlier death, not where fat is located on the body. But recent research on the wonders of the fat cell has shown that not all fat is alike. Fat around the middle is largely visceral fat, a type of deep fat that packs itself around internal organs and secretes powerful body chemicals. It's this type of fat that sets off reactions in the body that lead to changes in arteries, organs, and cells that result in heart disease, diabetes, and probably some cancers. The more abdominal fat, the greater the risk of developing these conditions earlier. "It's becoming clearer and clearer that body fat distribution is a critically important variable," says JoAnn Manson, chief of preventive medicine at Harvard University's Brigham and Women's Hospital. "And abdominal obesity is the key culprit."
Ideal look. To some extent, folk wisdom and popular culture have reflected this for centuries. A willowy waistline was an ideal for both men and women in colonial and frontier America and easier to attain when food was scarce and a great deal of physical activity was required to hunt, gather, and cook it. The Victorian period ushered in the era of the "hourglass figure," which remained the ideal female form for more than 120 years, until it was supplanted by the "Twiggy" look of the 1960s. Boys, of course, want thin waists, too. Many a late-night infomercial sells the dream of "six-pack abs" or a "washboard stomach" to men.
One thing is certain: The average American waistline is expanding. In fact, it has never been bigger. Federal health surveys show that over the past four decades, the mean waist size for men has grown from 35 inches to 39 inches; for women, from 30 inches to 37 inches. The National Institutes of Health recommends that men with waists measuring 37 inches or greater and women with waists larger than 31.5 inches modify their lifestyles to reduce their waists and resulting health risks. Nearly 39 percent of men and 60 percent of women are carrying too much belly fat.
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.
The connection between fat distribution and sex hormones is only now being explored. The apple shape "tends to be associated with higher male hormone levels in women, and this may be one of the reasons that men and women tend to have a different body fat distribution," says Manson. Men, who naturally have more male hormones than women, also accumulate fat around their waists more frequently than women. Though the role hormones play in fat distribution is not yet clear, the way many women lose their waist at menopause may be due to changes in the relative levels of androgen to estrogen. Clinical trials of hormone replacement therapy, however, did not show that postmenopausal women who took the drugs had a substantial waist-size reduction, says Manson.
Apple vs. pear. Conversely, the pear shape or the hourglass figure may be linked to higher estrogen levels and greater fertility. One study of Polish women indicated that those with large breasts, small waists, and wide hips had higher levels of estrogen than those who were more apple shaped. "It's possible that it's a fat distribution pattern [hourglass] associated with the higher likelihood of reproductive success, and it was something that was selected for" during women's evolution, says Manson.
Some recent studies also indicate that hip and thigh fat--common to pear-shaped people--may actually offer some unique safeguard against cardiovascular disease. "Hip fat is definitely protective," says Marie Savard, a Philadelphia internist who is researching the health effects of body shape. She points to a 2004 Danish study of nearly 3,000 men and women that showed that a larger hip circumference reduced cardiovascular disease and death among women but had no positive effect for men. Similarly, research on 3,000 older adults reported in the Archives of Internal Medicine earlier this year confirmed not only that abdominal fat leads to metabolic syndrome but also that leg and thigh fat--among both women and men--was associated with a lower prevalence of metabolic syndrome and less heart disease.
But not all researchers agree that hip fat is beneficial, and if it is, no one yet knows why. One theory is that hip and thigh fat may act as a metabolic reservoir, storing harmful blood fats that would otherwise circulate throughout the body. Or it could be that fat on the hips, thighs, and legs may just indicate that a person is genetically pear shaped and less inclined to gain the spare tire that plagues the more apple shaped. Still, more lower-body fat generally means more fat--period--which clearly leads to higher risk of heart disease and diabetes.
It will be decades before medicine unravels the metabolic puzzle that is fat. In the meantime, doctors say the important action to take is to stop waist expansion. "We all need to slow down this process of becoming more applelike," says Savard. "Body shape really does matter."