How Your Friends Make You Fat

The social dynamics behind obesity

Published: Aug 1, 2009 09:00:10 AM IST
Updated: Aug 1, 2009 09:09:12 AM IST

You arrive at a family function and your nagging aunt notes how you have become “healthy” since she last saw you. You respond pleasantly, wishing you had a better response for her. Now you do. As someone close in your social network, the fact that she is obese directly contributes to your current state of corpulence. In fact, a rebuttal that sends her straight to the dietician could be the best thing you can do for your own waistline. Let me explain.

Ever since Stanley Milgram showed the world was connected through six degrees of separation, scientists have been examining behaviours that are influenced through these social ties. One of the most striking observations is from Harvard and University of California, San Diego, where scientists showed that obesity can spread person to person. The scientists analysed interviews of over 12,000 people who were being followed through the landmark Framingham Heart Study at regular intervals over 32 years. In those interviews the participants were asked to name their immediate family members and at least one close friend. The study also gathered weight information on the participants. The dynamics that the investigators uncovered were striking!

Assume your nagging aunt is someone whom you would list as a friend, and who similarly would list you as one. In that case, as she becomes obese, your risk for obesity increases by over 150 percent. If your sibling sends his clothes to the tailor to be loosened, you better ask the tailor for a bulk discount. Your risk for obesity increases by 40 percent.

And finally, if your spouse becomes obese, your risk increases by 37 percent. Factors that explain this phenomenon could include an increased acceptability of obesity or direct influence of behaviours as someone close gains weight. It is important to share that closeness only matters in a social context; geographical proximity (literally) carries no weight.

The point of sharing this is not for you to rework your Facebook page, but to give some tips for those who want to lose weight. Recently, scientists from Colorado State University suggested four ways to use social networks to help shed some kilos.

First of all, broaden your social circle. Invite friends with friends of theirs you have not yet met for your dinner parties. All the invitees should be actively losing weight. This will dilute the effect of those in your networks who are not losing weight. Unfortunately, this strategy fails as the diets of the newcomers to your network begin to fail.

The second solution applies more as a public health intervention. The most highly connected individuals in any network will hold the greatest influence on the weight of its members. Celebrities are very highly connected with an influence that extends beyond hairstyles and brands. If celebrities are of mainly normal weight, mathematical simulations have shown that they will slow the rate of obesity. May be public health officials need a seat at the editorial table to have a say in who makes it to the cover of magazines!

A third approach encourages keeping a diverse social network, but including some people who will be easily influenced by others. This sounds counter-intuitive, but those easily influenced will quickly jump onto the weight loss bus and serve as catalysts to further influence others to lose weight.

A final approach involves changing the social forces around you. To do that, you first have to be aware of what these forces are. A new dating reality TV show on Fox in the US is one of these forces. More to Love is a show of “real women determined to prove that love comes in all shapes and sizes.” The influence of this show could be countered by choosing to run a marathon and actively encouraging those within your social network to keep a training regimen such as yours. Sign me up for that! n

Dr. Kumar, and our health team, can be contacted at

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(This story appears in the 14 August, 2009 issue of Forbes India. You can buy our tablet version from To visit our Archives, click here.)

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  • Kartika Das

    Nice! Very interesting concept.

    on Aug 7, 2009
  • Safa Natalie Sinelnikov

    Dr. Kumar: The information you present here is truly astonishing. I have been trying to lose weight by brute force, but I have never achieved any quality outcomes this way. Perhaps I need a more subtle approach! Thank you for your insights!

    on Aug 7, 2009