How do your friends affect your health?

The following column was written by Kimberly Burke,┬ádirector of CSU’s Adult Fitness Program

It is interesting to watch children form friendships because these interactions shape their personalities and behavior. The same can be said for adults as well. We often don’t realize how much we are influenced by our friends, peers, colleagues and family. These people make up a piece of our social environment and influence a lot of our decisions — from the clothes we buy to our health. Let’s take a deeper look at our social environment and health outcomes.

The group dynamic

We often try to focus on individual determinants of health. While we all impact our own health, there is also a group dynamic at play. As humans, we are constantly interacting with everything around us. Often called the Social-Ecological Model, this framework displays the interactions of individual, social and environmental factors. When one is altered, it can (and likely will) impact the other areas. Some of these interactions may be clear, like a neighborhood walking group that allows people to be physically active and get to know each other better. Some may be less obvious, like factors of our environment such as the 65 parks that exist within Fort Collins, and Colorado’s average 300-plus days of sun a year, which offer opportunities to get outdoors.

Running shoes outside

Social network

Thinking broader than just your friends on Facebook, your social network is constantly evolving and not just influenced by your five closest friends, but their friends, and their friends’ friends. Did you know that when your friends are obese, that increases your likelihood of being obese by 45 percent? When friends of friends are obese, you’re still at 25 percent increased chance of being obese. Even at the third tier (friends of friends of friends), there is still a 10 percent risk for you.

We can think of these interactions in several ways. One, if I gain weight, you as my friend gain weight. Our friends influence our behaviors and perceptions, so we could both put on extra weight because we often meet up for coffee or drinks. It could also be a matter of perception. We tend to change our own personal definition of what’s overweight based on how we or our friends appear. If a friend has put on a few extra pounds, we will change our view so that our friend’s appearance no longer fits into our definition of “overweight.”


The second interaction is the idea of homogeny — we gravitate towards people who are like us. More sedentary people tend to hang out with other less active people. And three, some confounding variable of a common environment, like lack of access to recreation centers or other opportunities to be active may have an influence on us.

Nicholas Christakis is a well-versed researcher in this field. All the statistics above are from his studies. Here’s a quote from his┬áTED Talk that displays the delicate interactions of our social network and health outcomes, “If we took time to realize and appreciate how complex our social networks are we’d be spending a lot more time nurturing them.”

So what does that mean for you and me? Should we ditch the friends with a BMI greater than 30 kg/m2? Absolutely not! It means that while our friends influence us, we also influence them. So if you want to impact the health of others, start impacting your own health. Your thinking and behavior will integrate its way into your social network and benefit everyone around you.

Kimberly Burke is the director of the Adult Fitness Program at Colorado State University, an outreach program through the Department of Health and Exercise Science. Adult Fitness offers exercise opportunities for employees of CSU as well as community members, while providing hands-on learning experiences for health promotion students. To learn more see