When one person gains weight, their close friends often follow. Researchers have just offered evidence in a study that says obesity  appears to spread through society. But the findings might also offer hope.  If friends help make obesity acceptable, then they might also be influential in losing the fat. The researchers note that support groups are already an effective tool in dealing with other socially influenced problems, like alcoholism .  The findings appeared in the New England Journal of Medicine. The researchers used information collected from 12,000 people. It was collected between 1972 and 2003 as part of the Framingham Heart Study.  The information was highly detailed. There was even contact information for close friends of the people in the study. The researchers examined more than 40,000 social ties. They found a person's chances of becoming severely overweight increased by 50% if a friend had become obese. A sister or brother of a person who became obese had a 40% increased chance of becoming obese. The risk for a wife or husband was a little less than that. Nicholas Christakis of Harvard Medical School was a lead researcher in the study. He says there is a direct causal relationship between a person getting fat and being followed in weight gain by a friend. The study found that the sex of the friends was also an influence. In same-sex friendship, a person had a 71% increased risk of becoming obese. Men had a 44% increased risk of becoming obese after weight gain in a brother. In sisters, it was 67%. The researchers also considered the effect of where people lived in relation to each other. James Fowler of the University of California was the other lead expert. He says a friend who lives a few hundred kilometers away has as much influence as one in the same neighborhood. He says the study demonstrates the need to consider that a major part of people's health is tied to their social connections. Both researchers say their research shows that obesity is not just a private medical issue, but also a public health problem. James Fowler seems to believe that  _   .
a friend who lives nearby affects us most one's health has nothing to do with friends social connections have effects on one's life a friend living faraway has the same influence as one's neighbor