This is SCIENCE IN THE NEWS in VOA Special English. I'm Barbara Klein.
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And I'm Steve Ember. This week, we will tell how friendship could be fattening. We also will tell about allergic reactions and their treatments. And, we report on a computer program that has solved a popular game.
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Researchers say they have found that fatness can spread from person to person in social groups. When one person gains weight, close friends often gain weight, too. The study was published last month in the New England Journal of Medicine.
The researchers looked at records from the Framingham Heart Study. It gathered health information about more than twelve thousand people from 1971 to 2003. The information was very detailed. It listed changes in the body-mass index for each individual. The body mass index measures a person's body fat.
The Framingham study also provided information about changes in family and events like marriages and deaths. There was also contact information for close friends of the subjects in the study. As a result, the researchers were able to examine more than forty thousand social ties.
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The study showed that when a person becomes severely overweight, there is a fifty-seven percent increased chance that one of their friends will be, too. A sister or brother of the overweight person has a forty percent increased chance of becoming fat. The increased risk for a wife or husband is a little less than that.
Nicholas Christakis of Harvard Medical School was a lead investigator in the study. He says his research showed that fat people are not choosing fat friends. He says there is a direct causal relationship between a person getting fat and being followed in weight gain by a friend.
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The study found that the sex of the friends is also an influence. In same-sex friendships, a person has a seventy-one percent increased risk of getting fat. The same was true for brothers and sisters separately. A man has a forty-four percent increased risk of becoming obese after a weight gain in his brother. In sisters, the increased risk is sixty-seven percent.
The study also showed that physical closeness of family members and friends did little to increase a person's risk. The other lead investigator was James Fowler of the University of California at San Diego. Mr. Fowler says a friend who lives a few hundred kilometers away has as much influence as one in your neighborhood. He says the study demonstrates the need to consider that a major part of a person’s health is tied to his or her social connections.
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Doctor Christakis and Mr. Fowler say close friends probably influence what a person finds acceptable and unacceptable. So if a friend gets fat, the condition becomes more acceptable. Both investigators agree their research shows that obesity is not just a private medical issue, bu
