Causes of Obesity in Men

It’s time to face up to what overeating and inactivity are doing to us

Medically Reviewed by James E. Gerace, MD on June 01, 2007
6 min read

The prevalence of obesity among American men has doubled in only 25 years, and it’s killing us. A 2004 survey published in the Journal of the American Medical Association found that 71% of men 20 years old and over were overweight and 31% were obese. The same survey conducted in the late 1970s had found 47% of men were overweight and 15% were obese.

Science is searching for the causes of obesity and exploring the role of genes, the diets of pregnant women, and the feeding habits of babies. But the bottom line is this: Most of us have settled into sedentary lifestyles and have trouble resisting the temptations of cheap, plentiful food our culture has served up.

It isn’t good to be fat, but there’s just so much good food and so many ways of entertaining ourselves from a swivel chair or a couch. As a result, a host of health issues linked to obesity threatens us unless we learn how to push back from the table earlier and head out the door for a walk or something faster more often.

“By the time you reach 35,” says George L. Blackburn, MD, PhD, “you don’t need to gain any more weight.” Blackburn holds the S. Daniel Abraham Chair of Nutrition at Harvard Medical School, and he tells WebMD that as men get older, muscle tends to be replaced by fatty tissue. Since fatty tissue doesn’t need the same amount of energy to maintain itself, you gain weight. But if you’ve gained more than 20 pounds since college, Blackburn says, something about your food selection and exercise program is out of balance. “You need to run, not walk,” he says, “to see a health care provider who’s experienced in finding healthy lifestyles.”

While women put weight on their hips, breasts, and limbs, men gather it around the waist, where it circulates through the liver, causing metabolic problems like diabetes. Added weight puts you at risk of heart attack, cancer, hypertension, and sleep apnea. It can also affect your sex life and make it harder to exercise and enjoy your kids.

How did we get so fat? “Obviously there’s a genetic component to obesity, “ says Barbara Rolls, PhD. Rolls holds the Helen A. Guthrie Chair in Nutritional Sciences at Pennsylvania State University. “But,” she adds, “the surge in obesity clearly can’t be due to genetic changes. We don’t evolve that quickly.”

That said, when it comes to getting fat, not all men are created equal. The genetic differences are clear from studies conducted by Claude Bouchard, PhD, of the Pennington Biomedical Research Center at Louisiana State University. Controlled portions of food were given over 100 days to sets of identical twins. While weight gain was similar for each pair of twins, it varied dramatically among the pairs. Some sets of twins gained as few as eight pounds during the “overfeeding” experiment, while others put on as much as 26 pounds.

We all know a few men who can quaff and stuff it all in their wooden legs and still weigh what they did in college. Some people are more predisposed to gain more weight than others, and research indicates that gaining weight rapidly as an infant is associated with a higher risk of adult obesity.

“We don’t know whether the weight gain in infancy is a cause of obesity, or whether they are both controlled by the same gene or perhaps by cultural practices,” says Nicolas Stettler, MD, MSCE, a professor of pediatrics at the University of Pennsylvania. But it may well be that some of us developed metabolic patterns in infancy that continue to influence our eating habits throughout life.

But genes don’t explain the increase in obesity. “I think we can safely say that at the end of the day, the cause of obesity is eating more than you need for your physical activity,” says Stettler. “We eat more, and the availability of more sedentary entertainment leads people to be more sedentary.”

Men eat 70% more at a sitting than women do, Rolls tells WebMD. But, she says, men are “the primordial eating machines.” They tend to listen to their bodies more while women eat what they think they are supposed to eat.

The biggest change in eating habits, Rolls believes, is portion size, which started growing in the 1970s in restaurants and recipe books. Then supersizing really took off in the 1980s. It might seem logical to assume that when a person eats a really big meal that person will back off on subsequent meals or days. But Rolls’ research has shown this not to be the case.

At her laboratory, she feeds human test subjects large portion sizes without telling them and observes how they respond. They respond by pigging out. Over a period of 11 days, in a recent experiment, the overfed group sucked up 5,000 more calories than the “control” group, which was given healthy, complete meals but with half the portion size.

Obviously, there are vested interests in favor of selling more food and drink, even if that does help fuel the obesity epidemic. “From the popcorn stand in movie theaters to fast food, we’ve been had by the most skilled advertising people in the world,” says Blackburn. “They keep telling us that it’s our right to be instantly gratified. Well, there’s a sucker born every minute, and you’re a sucker to let yourself gain more than 20 pounds in 20 years.”

When it comes to finding solutions to the fat epidemic, Rolls has done some pragmatic thinking. Her research told her that it would be difficult to convince people to eat smaller meals. So what she has done is focused on encouraging them to eat less energy-dense meals.

A bowl of Cheerios, for example, provides the same calories as a couple tablespoons of granola. But, as she points out in The Volumetrics Eating Plan: Techniques and Recipes for Feeling Full on Fewer Calories (Morrow Cookbooks, 2005),eating the larger portion of Cheerios is more satisfying than eating the smaller portion of granola. “Bigger is better if it’s low-cal,” Rolls says. “Big portions of salad and soup can fill you up and displace other, more energy dense foods.”

Blackburn applauds Rolls’ book. But he also thinks the government should intervene to encourage healthier eating by charging a tax on junk food and offering incentives for buying healthy food. “But the people who own the junk food are not going to let you do that,” he says. “They’ll say people like me are crazy and it’s your right to have a miserable life and be able to pig out.”

Genetic research holds out the hope that in 10 or 20 years there may be new drugs to treat obesity. But there are more than 25 candidate genes involved in abnormal weight gain, and each person may have 12 or so of them, all making a very small contribution. So it’s unlikely that drug companies will find blockbuster drugs that can counteract the effects of all these genes together. “It will be very hard to have a medication driven by your personal predisposition,” says Bouchard.

In the meantime, though, according to Blackburn, “The craziest thing you can do is to overeat and under-exercise.”