Why We're Fat
Gender and age matter more than you may realize
Isn't it just like a man? Although his 56-year-old wife, Maureen, had been counting calories since her teens, Tom Javaux ate what he wanted and remained trim well into middle age. When the 62-year-old retired bricklayer finally developed a paunch and went on the same diet as his wife, he dropped more weight and lost it faster than she did--50 pounds to her 35.
Another injustice between the sexes? You bet. The latest obesity research shows that men and women differ in almost every respect when it comes to weight over the course of a lifetime: when they gain it, where they gain it, and at what rate. In women, sex hormones wreak havoc on the ability to control appetite, energy expenditure, and fat storage. In men, it is the slowing down of physical activity that tends to add pounds. But overweight men, because of where they carry their weight, can be at higher risk than women for heart disease and other serious health problems.
Despite the differences, the body shapes of both sexes share one alarming similarity: Both men and women are getting fat in epidemic proportions. Well over half of all American adults--about 63 percent of men and 55 percent of women age 25 and older--are overweight. Last week, in a special issue devoted entirely to obesity, the Journal of the American Medical Association reported new statistics that are nothing short of astonishing for a nation seemingly so obsessed with health and fitness: The rate of obesity--18 percent--has soared from 12 percent just seven years ago, making the United States now secure in its position as the fattest nation in the developed world.
"This rate is shocking," says Jeffrey Koplan, director of the Centers for Disease Control and Prevention, "and it means that we have a huge public-health problem." Indeed, depending on weight and age, obesity significantly increases the risk of high blood pressure and high cholesterol, diabetes, and gallbladder disease.
Obesity is determined by a measure called the body mass index, or BMI, which tallies weight adjusted for height. A BMI of 18 to 24.9 is considered normal, 25 to 29.9 is overweight, and 30 or higher is obese. A woman 5 feet, 5 inches tall who weighs 162 pounds is considered overweight; if she weighs 186 pounds she is obese. A 5-foot, 10-inch man who weighs 188 pounds is overweight; if he weighs 216 pounds he is obese. Both the overweight man and the overweight woman have BMIs of 27; the obese pair have BMIs of 31.
The prevalence of obesity may be troubling, but it shouldn't be all that surprising. As a species, humans have evolved with instincts to seek and store fat. Easy fat storage is crucial for survival in times of famine, yet for decades Americans have been seated at a veritable feast. Says Tom Wadden, director of the Weight and Eating Disorders Program at the University of Pennsylvania, "Now it has become a maladaptive trait because we are living in times when we have a surplus of food." As a result, he says, "we are all getting obese."
The good news is that if men and women know when they are most likely to fatten up--and why-- they can take steps to avoid the extra pounds.
For women, the lifelong battle against the scale starts in the teen years. Sex hormones kick into gear, preparing girls to nurture babies by causing an explosion of fat on the hips, buttocks, and chest. Teenage girls are notoriously conscious of their weight, says Wadden--and, as it turns out, for good reason. Before adolescence, girls have no more than 12 percent body fat. Afterward, they have as much as 25 percent. That's the average amount for an adult female who is not overweight, but the change often comes faster than girls can emotionally adjust.
By contrast, late-adolescent boys, whose hormones are geared more toward muscle development, have only about 15 percent body fat. They can eat three helpings of dinner seemingly without effect, because muscle burns more calories than fat. "Boys are a different kind of engine," Wadden says.
Teen boys tend to be more physically active than teen girls. But a decrease in physical activity among both sexes is contributing to a recent 70 percent increase in the rate of obesity among young adults. Only 25 percent of U.S. high schools offered daily physical education classes in 1995, down from 42 percent in 1991. Girls, who tend to see exercise in terms of weight management, are less active than boys, who participate more for the joy of competition.
School lunches aren't helping. Though federal guidelines instruct public schools to limit fat to a third of the total calories in their lunch programs, many districts offer fast-food carts, with fries and burgers, because students clamor for them. Moreover, even though Americans have decreased fat consumption from 42 percent to 34 percent of their diet over the past 30 years, they still eat too much sugar and processed carbohydrates. And the weight added by all that white bread and pasta takes its toll immediately: The average 20-year-old, says David Ludwig, director of the obesity program at Children's Hospital in Boston, already shows signs of hardening of the arteries.
The reproductive years, from the 20s to the 40s, are belt-loosening times for both sexes but for different reasons. Just being married causes men to gain weight, but not women. "We found that married men were significantly fatter than men who had never been or were previously married," says Jeffery Sobal, a nutritional sociologist at Cornell University who conducted the study. Men eat more when they are married, the study showed, and they spend less time playing organized sports. (On the whole, though, men get a tremendous health boost from being married, Sobal says. They drink less, often quit smoking, use fewer drugs, and, in general, engage in less risky behavior.)
For women in this age bracket, pregnancy is of course the main cause of excess poundage. But new research shows that when those extra pounds are gained may determine whether the weight stays or goes after baby arrives. Weight gained in the first 20 weeks of pregnancy hangs on six months postpartum, says Jennifer Lovejoy, associate professor with the Pennington Biomedical Research Center in Baton Rouge, La. The weight put on after 20 weeks contributes to the weight of the baby and is less likely to stick around, Lovejoy says. One study found that those women who retained weight post-pregnancy had gained twice as much in the first 20 weeks as the women who did not retain weight, even though both groups gained the same amount over the nine months. This doesn't mean women should be dieting in the early stages of pregnancy, but at the same time, pregnancy is not an invitation to raid the refrigerator. Eating healthily while staying within the recommended guideline for weight gain (roughly 30 pounds for a woman of normal weight, less for overweight women), is the way to go.
Women are also at a disadvantage after giving birth, says Wadden of the University of Pennsylvania, simply because they spend more time than men do around food. "[Women] tend to be grazers, and over the course of a day they can easily pick up an extra 500 calories." African-American women need to be particularly careful, notes a study in this week's Journal of the American College of Cardiology. Just the slightest weight gain, researchers found, puts them at higher risk of hypertension and heart failure.
Exercise can help, but here again women have a harder time than men. Tracy Horton, at the University of Colorado's Center for Human Nutrition, found that men and women use up fat at different rates during exercise. Women tend to burn relatively more fat. But in the hours after a workout, that may come back to haunt them, Horton says. Women's bodies can detect the fat deficit and so try to replenish fat stores as soon as possible by putting fat from meals right back on their thighs and hips. Men, on the other hand, burn more carbohydrates, so their bodies are more likely to hold on to new carbos and less likely to hang on to the fat. It may not be fair, but ultimately, women simply have to restrain their intake of food more than do men.
As if wrinkles and gray hair weren't enough, men and women in their 50s are more likely to be obese than at any other time of their lives. And where that fat sits on the body matters. The potbelly that men often grow in their middle years is not just unattractive, it's dangerous--considerably more so than the fat that women typically carry on their hips, thighs, and arms.
The midlife paunch, which doctors call "visceral fat," poses a risk because it surrounds the internal organs. It releases fatty acids that make their way into the liver, diminishing the organ's ability to process the hormone insulin, eventually causing diabetes. The fat also affects how the kidneys process insulin, a factor that scientists say may lead to high blood pressure. For every 10 percent increase over normal weight, men and women have about a 20 percent jump in risk for heart disease.
For women, these middle years can be a double whammy. In menopause, when women stop producing estrogen, gravity pulls down on hips, thighs, and buttocks, but abdominal fat often starts creeping upward. "This may be why, after menopause, the rate of heart disease in women equals that of men," says Aviva Must of Tufts University School of Medicine. Before that the rate of heart disease in women is significantly lower than that of men. Fortunately, hormone replacement therapy can minimize this abdominal weight gain.
As men and women reach their 60s and beyond, their body weight typically starts to decline. "As we get older we lose lean tissue, or muscle mass," Must says. "We have less body mass and less caloric need, so we gradually lose weight." Chronic diseases and medications can also interfere with appetite, as can depression and a diminished sense of taste. Weight-bearing exercises will help maintain muscle mass and keep the body strong. Weightlifting is especially important for women because it can stave off osteoporosis by maintain- ing bone density--and because women have less muscle to lose to begin with. "If a woman loses a significant portion of her muscle mass, she will be far weaker than a man who loses the same amount," Must says.
Ultimately, being overweight is likely to lead to premature death. People who are severely overweight are four times as likely to die before their expected lifespan, and people who are moderately overweight are twice as likely to die early. So the Javauxs take to the track together, walking a mile twice a week. She is slower than he, and she says most people on the track pass her by. But, she says, "We really want to succeed. I'm doing it for him, and he's doing it for me." It just may take her a little longer, and she may have to work a little harder to get there.
The years take shape
How and where we gain weight have to do with age and sex
CHILDHOOD. Lessons learned young can be hard to break. Poor eating habits have caused a huge surge in kids' rate of obesity
PUBERTY. Teenage girls obsess about their weight with good reason. They change from 12 percent fat to 25 percent fat virtually overnight.
PREGNANCY. Weight gained early in pregnancy may be harder to take off later. And men get fatter just by being married.
MIDDLE AGE. These are the danger years, especially for men. Weight carried around the middle is more dangerous than weight on arms and thighs.
OLD AGE. Both men and women lose muscle and bone mass. Appetite wanes, and hormonal protections disappear. Limbs get skinny.
Heavyweight states
States with high percentages of overweight* people tend to be those lightest in their wallets. It may be that fresh fruits and vegetables are harder to find in less affluent areas.
THE HEAVIEST
West Virginia 37.8
Mississippi 37.5
Alaska 36.2
Louisiana 36.1
Alabama 35.8
Kentucky 35.8
THE THINNEST
Arizona 22.5
Massachusetts 26.9
Nevada 27.0
Colorado 27.2
Connecticut 27.4
Vermont 27.4
*People with a body mass index between 25 and 30, taken from U.S. Department of Health and Human Services data
With Josh Fischman
This story appears in the November 8, 1999 print edition of U.S. News & World Report.