Obesity rate will reach 42 percent, Harvard researchers say

If you thought Americans couldn't possibly get any bigger, think again.

Researchers at Harvard University say America's obesity epidemic will continue to spread until at least 42 percent of adults are obese, according to a new study.

That conclusion defies some experts' claims that the obesity rate in the U.S., settled at 34 percent for the past five years, has peaked.

According to the federal government's Centers for Disease Control and Prevention, another 34 percent of American adults are classified as "overweight" but not "obese."

"Our analysis suggests that while people have gotten better at gaining weight since 1971, they haven't gotten any better at losing weight," study lead author Alison Hill said in a statement. "Specifically, the rate of weight gain due to social transmission has grown quite rapidly."

The researchers arrived at the estimate by applying mathematical modeling to 40 years of Framingham Heart Study data.

What they found is that obesity is proliferating among American adults through social networks. No, that doesn't mean Facebook -- rather, that means that you're more likely to be obese if your friends are, too.

Researchers David Rand, Martin Nowak, Nicholas Christakis and Hill categorized obesity's spread in three ways:

• The rate at which obesity spreads person to person.
• The rate at which obesity spreads through non-social means, such as through unhealthy foods or sedentary lifestyles.
• The rate of "recovery" from obesity -- weight loss that returns a person's body mass index, or BMI, below 30.

The best-case scenario? America's obesity rate could rise above 42 percent of adults. One caveat is that it could take four decades for that shift to occur, a more gradual increase than what's been experienced in the last 40 years but frightening nonetheless.

The researchers also found that a non-obese American adult has a 2 percent chance of becoming obese in any given year. For every obese social contact, the number rises by 0.4 percentage points.

Have five obese friends? Your risk of becoming obese has doubled.

Interestingly, an obese adult has a 4 percent chance of losing enough weight to return to the "overweight" category. The problem: this figure has remained constant since 1971.

Their work was published this week in the journal PLoS Computational Biology.

This post was originally published on Smartplanet.com