Why We're Fat
Gender and age matter more than you may realize
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.
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