Obese Friends, Family Boosts Personal Obesity Risk

Obese 'network' can extend to three degrees of separation

WEDNESDAY, July 25 (HealthDay News) -- People who have obese siblings, friends or spouses are more likely to become obese themselves, researchers report in the July 26 issue of the New England Journal of Medicine.

Nicholas A. Christakis, M.D., Ph.D., from Harvard Medical School in Boston, and James H. Fowler, Ph.D., from the University of California San Diego, examined whether weight gain in one person was associated with weight gain in their siblings, spouses, neighbors and friends in 12,067 socially connected individuals from 1971 to 2003.

The researchers found clusters of obese persons (body mass index of 30 or more) that extended to three degrees of separation. Having an obese friend increased the risk of becoming obese by 57 percent, having an obese sibling increased the risk by 40 percent, and having an obese spouse increased the risk by 37 percent. The influence was greater among people of the same gender.

"Networks, in this case those that pertain to social influence, may have just as strong an impact on the development of obesity as the otherwise strong genetic effects," Albert-Laszlo Barabasi, Ph.D., from the University of Notre Dame in Indiana, writes in an accompanying editorial.

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