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Obesity Spreads Through Friends, Family, Study Finds

People whose friends and family members gain weight are more likely to become obese themselves, according to a study in this week's New England Journal of Medicine. NewsHour health correspondent Susan Dentzer discusses the findings.

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  • JIM LEHRER:

    Now, the surprising connection between family, friends and obesity. That idea was outlined today in a study published in the New England Journal of Medicine. Researchers found that a risk of obesity seems to significantly rise through personal relationships.

    Our health correspondent, Susan Dentzer, is with us now. Susan, welcome.

  • SUSAN DENTZER, NewsHour Health Correspondent:

    Thank you, Jim.

  • JIM LEHRER:

    Take us through this. How would an association with family and friends cause you to be obese?

  • SUSAN DENTZER:

    Well, Jim, the researchers who did this study, Dr. Nicholas Christakis from Harvard, who's a medical sociologist, and James Fowler, his colleague, who's a political scientist from the University of California, San Diego, looked at the fact that we have, as we know, an obesity epidemic. And they asked, "Gee, could this be spreading the way a flu epidemic spreads?"

    And so what they did is they went to a very valuable source of data, which is the long-term Framingham Heart Study. That's the study that, over many years, has looked at risks of heart disease, originally based in Framingham, Massachusetts, and evaluated people over the years to see what happens, what happens when they gain weight, et cetera, et cetera.

    An interesting facet of that study is that people were all asked, "Who are your friends? Who are your relatives? Who are your siblings?" Partly just so the researchers can keep in touch with people over years, so they had all these records of the people in the study. And it turns out that, when they name their friends or relatives, because it was in Framingham a lot of those people were in the study, too.

    So what you ended up was this large group of people in the study, in this study 12,000 people, who were all friends or relatives of each other, and they were able to track what happened as these people were assessed, particularly for their weight, over a period from 1971 to 2003. They took that data; they built a statistical model on a computer and basically found that, looking across these various associations, you see these connections.

    For example, if your spouse is obese, the risk that you will become obese increases by 37 percent. If your sibling is obese, becomes obese over time, the risk that you will become obese increases by 40 percent. If your friend becomes obese, the risk goes up by 57 percent. And if both of you are kind of close friends, you basically both name each other as your friend, the risk can rise as much as 171 percent.