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More Obesity News: Obesity Spreads Through Social Networks

by Kristen King on July 26th, 2007

New findings released by the NIH and published in a recent issue of the New England Journal of Medicine characterize obesity as being “socially contagious.” Translation: The more fat friends you have, the more likely you are to become fat. The same is true for slim pals.

At first I thought, “Well, people tend to gather in like groups, so these must be faulty findings. But this quote in a press release from UC San Diego set me straight: “It’s not that obese or non-obese people simply find other similar people to hang out with,” said Nicholas Christakis, MD, PhD, a physician and a professor in Harvard Medical School’s department of health care policy. “Rather, there is a direct, causal relationship.”

Look after the jump for a summary of the findings and links to two more press releases.

Reported by Harvard Medical School:

“What we see here is that one person’s obesity can influence numerous others to whom he or she is connected both directly and indirectly,” says Nicholas Christakis, MD, PhD, a professor in Harvard Medical School’s Department of Health Care Policy. “In other words, it’s not that obese or non-obese people simply find other similar people to hang out with. Rather, there is a direct, causal relationship.”

…Gender played an important role in how these statistics broke down. In same-sex friendships, individuals experienced a 71 percent increased risk if a friend of theirs became obese. This pattern was also observed in siblings. Here, if a man’s brother became obese, his chances of becoming obese increased by 44 percent. Among sisters, the risk was 67 percent. Friends and siblings of opposite genders showed no increased risk. While the researchers note that correlations among siblings provide evidence for a biological, and possibly even a genetic, component to obesity, patterns seen among friends indicate that there’s more than biology at work.

Reported by the NIH and the National Institute on Aging:

A key participant’s chances of becoming obese increased by 57 percent if he or she had a close friend who became obese. In same-sex friendships, a close friend becoming obese increased a key participant’s chance of becoming obese by 71 percent. However, no such association was found in opposite-sex friendships.

The perception of friendship also was an important factor. When two people identified each other as close friends, the key participant’s risk of becoming obese increased by 171 percent if his or her friend became obese. In contrast, a key participant was not likely to become obese if someone claimed a close friendship with him or her but the key participant did not report the friendship.

Among pairs of siblings, one’s becoming obese increased the other’s chance of becoming obese by 40 percent. This finding was more marked among same-sex siblings than opposite-sex siblings.

In married couples, one spouse’s becoming obese increased the likelihood of the other spouse becoming obese by 37 percent. Husbands and wives appeared to affect each other equally.

Obesity spread across social ties, despite geographic distance from one person to another. Further, social distance–the degree of social separation between two people in the network–appeared to make more of a difference than geographic distance in the spread of behaviors and norms associated with obesity. An immediate neighbor’s becoming obese did not affect a person’s risk of becoming obese.

So what do you think? Does this study have merit? Do you see patterns around you that make you believe it’s legit or just a coincidence? Leave a comment!

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POSTED IN: New research, Obesity, Relationships