Obesity is certainly not contagious in the infectious sense, like a virus. However, while obesity cannot be physically caught from others, there is some evidence to show that it is socially contagious. An important study found recently that if a person has obese friends, he or she is also likely to become obese.
The study examined 12,067 Framingham, Massachusetts residents between 1971 and 2003. It was headed by James Fowler of San Diego's University of California and Dr. Nicholas Christakis of Boston's Harvard Medical School. Dr. Christakis is a professor of medical sociology and he concluded from the study that obesity is collective in scope. He thinks that a key reason people with obese friends are likely to be obese themselves is the social acceptance of obesity within their social circle. The study also found that if their friends lose weight, a person is also more likely to lose weight.
Interestingly, Christakis and Fowler's study found that while family members such as spouses and siblings were somewhat influential in terms of obesity, friends were highly influential. A 37% increase in the risk of obesity was found if the person had an obese spouse, a 40% increase if a sibling was obese and a 57% increase if a friend was obese. The news that social networks may be a major influence in the spread of obesity caused some controversy.
Some people responding to the results of the study said the idea that obesity is socially contagious will only make obese people feel more like social misfits. They thought that more people would discriminate against obese people and would be less likely to socialize with them for fear of becoming obese themselves. There is a concern that people will take the study as a "warning" to not become friends with obese people.
However, other respondents to Christakis and Fowler's obesity study thought that the study just confirms the notion that social groups do affect how a person sees themselves. They argue that people within the same social network tend to approve of the same types of things that people in other networks may not. Also, as the study shows that when their friends lose weight, a person is also likely to lose weight, it is clear that the influence of a social network can be either positive or negative.