U.S. Adult Obesity Rate Expected to Climb to 42 Percent

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While recent estimates have claimed that as many as a third of Americans are obese, that isn't the worst of it. According to a new study out of Harvard University, the U.S. population is going to keep getting fatter until 42 percent of adults can claim the title of "obese." And the reason for the increase may be as simple as who we hang out with.

Obesity is defined as weighing 20 percent or more above ideal body weight or having a body mass index of 30 or higher. BMI is figured by taking a person's weight in pounds times 703 and dividing it by height in inches squared. According to the Centers for Disease Control and Prevention, not only are a third of Americans obese, but another third are overweight, which is defined as a BMI of 25 or more.

Researchers at Harvard concluded that people who socialize with people who are obese are more likely to become obese as well. The study used mathematical modeling with data from the Framingham Heart Study to determine that obesity appears to spread, almost the same way an infectious disease does. The research was published in the most recent issue of PLoS Computational Biology.

"We don't know what's at work here," lead study author Alison Hill, a graduate student in biophysics at Harvard, told AOL Health. "This study opens up an interesting new area." Hill says there's a lot of room for speculation, including the idea that people may adopt the habits of friends or that socializing with overweight people shifts a person's own sense of what represents a social norm.

The only problem with that kind of reasoning is that slimness doesn't have the same contagious effect, according to the study. Hill is quick to note, however, that her background is mathematical modeling, and she has no expertise in the biological factors that lead to obesity.

Dr. Michael Wolfe, chairman of the Department of Medicine at MetroHealth in Cleveland, doesn't buy the idea that this study will hold up scientifically. "I'm a basic scientist for a reason," he told AOL Health. "In these kinds of studies, you'll find the exact opposite next week." He feels it's true that one's social network will influence one's size, regardless of whether that network is thin or fat.

"If everyone around you is obese, it becomes more socially acceptable to be obese," he explains. "Aberrant behavior is more acceptable when others do it."

So does this study mean you should dump your fat friends? Well, not exactly. "A more positive way to look at it is that it's in your own best interest to help your friends lose weight," says Hill. That means if you and your girlfriends typically bond over pizza and ice cream, perhaps a few shared laps around the park might serve all of you better.

Hill said she would also like to emphasize that the social factors that lead to obesity don't appear to be nearly as significant as environmental factors. That means that regardless of how big your friends are, your own eating and exercise habits, genetic make-up and overall health still play the biggest role in what numbers you'll see when you step on that scale.

Wolfe says we all need to make an effort to fight our basic biology, which has designed us to be absorbers and storers of fat. "If you're full, stop eating," he says. "Put your utensils down between bites. Eat more slowly. And never waste calories on drinks."

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