So depending on a man's network of friends, he's just as likely to be chomping down wings and guzzling beer while watching the game as he is to be shooting hoops with the boys.
If heavy friends can make someone gain weight, can thin friends make someone shed the flab? Not necessarily, say the researchers -- but it might be worthwhile to start a diet or lifestyle change in groups.
"The public needs to know that it's very important to get your friends and family on board when making a lifestyle change," said Amy Wachholtz, a medical psychiatrist with the Duke Diet and Fitness Center.
"You are more likely to be successful if you have friends and family members to support you," Wachholtz said. "It's not just size of social network but also how committed they are to losing weight. Getting a friend who's also very committed is going to help you."
Jennifer Nelson, director of clinical dietetics at the Mayo Clinic, agrees. "Social networks definitely have an effect. This is something to be aware of for both the patient and the health care provider," she said.
"We as health care providers should be mindful of addressing the social group, not just the individual."