By Bob Condor

Social networks are all the rage on the Internet these days, and not necessarily all to the positive. But researchers from Harvard Medical School and the University of California-San Diego are making a strong case that social networks—the real thing, interaction between humans face-to-face—might be an underlying secret to how people develop health habits.

Harvard professor Nicholas Christakis and UC-San Diego researcher James Fowler teamed up last year to show that people become obese in social clusters. Now Christakis and Fowler come with May 2008 findings that people quit smoking by social associations too.

If you think about it, there is considerable logic to explain why people might influence each other to become fat or finally kick a nicotine habit that presents indisputable and potentially horrific health outcomes.

What makes the Christakis-Fowler research so fascinating is that members of the social network don’t necessarily know each other to be influenced. The decidedly American concept of staunch individualism doesn’t hold in the obesity or smoking studies, both of which draw data from the famed Framingham Heart Study that first began in 1948.

“We’ve found that when you analyze large social networks, entire pockets of people who might not know each other all quit smoking at once,” says Christakis, who with Fowler has painstakingly retrieved information from archived, handwritten administrative tracking sheets to connect more than 5,100 people with each other.

Some of those associations were predictable if not still instructive: One spouse quitting will persuade the remaining smoker-spouse to quit about two out of every three times. A fellow co-worker or friend can influence a person to quit smoking about a third of the time.

Here’s where it get tingly: The researchers found positive outcomes among people in “quitting cascades.”

A quitting cascade is a string of individuals who all kick the cigarette habit yet don’t the others directly. For instance, a quitting cascade might include three people, Moe, Curly and Larry. Moe and Curly are stooges, er, friends. Curly and Larry are friends. Moe and Larry have never met and don’t know the other. Moe and Larry smoke; Curly does not.

So Larry quits smoking. What Christakis and Fowler calculated from the data is that Moe’s chances of giving up smoking will increase by 30 percent even though he doesn’t know Larry or hasn’t the slightest idea that Larry has quit smoking.

And remember: Curly doesn’t even smoke. It does appear, said Christakis, a very smart guy who will publishing cutting-edge research for years to come, that Curly, the friend who knows both men, is some sort of “carrier” for social norms.

In this case, social norms have increasingly marginalized smokers in our society. As for obesity, unfortunate as it may be, social norms lead to higher acceptance of people who are overweight.

Christakis said social networks can work in our favor. “What people need to understand is that because our lives are connected, our health is connected,” he says.

Here’s the Daily Health Blog bottom line on this intriguing line of research. We are not in this alone, even when it most feels that way. There is a great and healthy force in connecting with others, even if we don’t everyone on a first-name basis. When trying to make positive health changes, knowing there is a social network-slash-safety net for any stumbles can be reassuring.

There’s strength and comfort we can draw from Moe, Curly and Larry.

“Bob Condor is the Daily Health Blogger for Barton Publishing. He is also the Living Well columnist for the Seattle Post-Intelligencer. He covers natural health and quality of life issues and writes regularly for national magazines, including Life, Esquire, Parade, Self, and Outside. He is a former syndicated health columnist for the Chicago Tribune and author of six books, including “The Good Mood Diet” and “Your Prostate Cancer Survivors’ Guide.” He lives in the Pacific Northwest with his wife and two 11-year-old kids.”