Scientists Claim Your Friends Can Influence Your Weight, and It’s Curious to Learn Why

Yes, this is a scary but real story. Your friend, your boyfriend, your sister’s friend, or your sister herself can influence your weight.

Like with any other contagious disease, the secret is preventing it. You must be very aware which is why we at Bright Side have decided to explain how this happens and what you can do to avoid it.

Scientific basis

In a study published by the New England Journal of Medicine, it is stated that obesity responds to a pattern of social contagion. This idea was postulated by 2 researchers, Nicholas A. Christakis and James H. Fowler, who analyzed the tendency to repeat behaviors among social networks. Their case study was on 12,000 adults and their social relationships. For this, they created a map with dots and lines representing the social connections of these people. Graphically, when a dot became bigger, or in other words, became fatter, the dots around it also did.

The risk

The graph determined the percentages of probabilities of contagion. Thus, the risk of you suffering from obesity will increase by 57% if your friend starts to gain weight, by 40% if it’s your sister, and by 37% if it’s your partner.

3 degrees of separation

We have already understood that obesity can be transmitted dramatically, but you won’t catch obesity by crossing the street with a person who is overweight. According to the researchers, this epidemic reaches up to 3 degrees of separation. That is, if the friend of your friend’s friend’s friend becomes overweight, it will not affect you because the social separation is much wider.

No matter the distance, it can still be contagious.

For the authors of this research, social distance is more relevant than the actual geographical distance. They showed that if the social bonds are strong, even if the person is miles away from another person who suffers from obesity, they have the same percentage of risk as if they lived nearby.


The study explains its finding from the standardization of what a suitable body mass is, that is, some people may think that it is okay to be overweight if those around them are also overweight. “You form an idea of what an acceptable body is according to what you see around you,” explains Christakis.

It’s not the only reason.

Of course, body mass is not gained solely by seeing how another person gains weight. It is due to eating habits and lack of exercise; medical, genetic, and environmental circumstances, and even food policies. This study is just an indication of the social reason why we stop paying attention to our body and its needs.

Has this contagious weight gain ever happened to you? Tell us about your experience.

Preview photo credit Friends / Warner Bros.
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