Don't Let Friends Make You Fat This Holiday Season

America's obesity rate won't start leveling out until a whopping 42 percent of the population is obese, according to a new Harvard study published this month. Bummin' over the report? Don't look to a friend's shoulder to cry on. The study also found that our buddy systems are somewhat on the hook for our bulging belt lines. "Our analysis suggests that while people have gotten better at gaining weight since 1971, they haven't gotten any better at losing weight," says lead author Alison L. Hill, a graduate student in Harvard's Program for Evolutionary Dynamics as well as the university's biophysics program. "Specifically, the rate of weight gain due to social transmission has grown quite rapidly."

With the holidays right around the corner, it might seem tougher than ever to keep your portions in check. But keep reading—help is on the way!

Do This to Prevent Holiday Weight Gain

The details:

Researchers used mathematical data derived by applying mathematical modeling to 40 years of Framingham Heart Study data and in its best-case scenario predicted a national obesity rate of 42 percent over the next 40 years. The researchers found that while easy access to unhealthy food and portion sizes is largely to blame for the increase in body mass over the last four decades, but noted that our social circles are accelerating those gains.

Non-obese people face a 2 percent risk of becoming obese in any year. For each obese friend, your chance increases by a half of a percent. The study appeared this month in the journal PLoS Computational Biology.

What it means:

The new report runs contradictory to Centers for Disease Control and Prevention numbers that suggest the obesity rate in the U.S. has already plateaued at 34 percent, the rate that's been intact for five years. (An additional 34 percent of Americans are considered overweight, which is defined as having a body mass index between 25 and 29.9; 30 or higher is considered obese.) And while the increase is expected to come about more slowly than the previous spike in the national obesity rate, it's still problematic because obesity is linked to many serious and expensive-to-treat health problems like cancer, heart disease, diabetes, metabolic syndrome, and even early death.

5 Signs You're Headed for a Holiday Breakdown

So how are our friends doing this to us?

Psychologist Jeffrey Rossman, PhD, director of life management at Canyon Ranch in Lenox, Massachusetts, points out three main reasons why people put on weight if their friends are heavier:

1. People gauge what is normal by looking at others in their social circle. If they gain a few pounds, they don't worry about it because they feel they fit in with their peers.

2. People eat with others in their social circle and are influenced by their friends' eating behavior.

3. People's choices of recreational activities are influenced by other people in their social circle. If you and your friends get together to take walks, hikes, and bike rides, you'll probably be thinner than if you and your friends primarily get together for lunch, dinner, or drinks.

Here's how to avoid contributing to the growing obesity rate—especially with the holidays right around the corner:

Eat early, eat often.

While you may be tempted to save all of your calories for a holiday food bender, you'll actually feel like eating less during a holiday meal if you eat something full of fiber, such as oatmeal, for breakfast, along with other healthy snacks like walnuts throughout the day. If you can, start your holiday morning off right with a walk, jog, or bike ride.

Focus on people, not pie.

At a holiday function, make your first order of business catching up with friends and family without carting around a plate of chips and dip. Interesting conversations could prove to be more fulfilling than junk food, says Rossman.

How to Prevent a Holiday Hangover

Once hunger does strike and you're tempted to load up on sweets, focus on your gut to determine if you're really hungry. Before filling up a plate, take a short walk or find someone interesting and strike up a conversation, Rossman suggests.

Plan an active activity.

If you can, start your holiday morning off right with a walk, jog, or bike ride. You could even start a family or friendship tradition: Plan a nature outing, a walk, or a sledding, skating, skiing, hiking, or caroling holiday event to get moving.