Behavior is socially contagious, according to a study of more than 5,000 residents of a town in Massachusetts.

Social scientist Nicholas Christakis and political scientist James Fowler studied personal records of 5,124 men and women who were part of the Framingham Heart Study that was started in 1948. The still ongoing study by the National Heart, Lung and Blood Institute and Boston University led to the identification of major cardiovascular diseases risk factors and their effects such as blood pressure, cholesterol levels, age, gender and psychosocial issues.

HAPPY RUNNER. A study has uncovered that behavior, whether good or bad, can spread through social networks. Happiness and even obesity can spread through a circle of friends and family members. (Photo during Subic International Marathon by Marlen Limpag)

Christakis and Fowler found that:

• Obesity spreads through social networks like a virus
  When the study started in 1948, fewer than 10 percent of the town’s residents were obese. By 1985, the number of obese people went up to 18 percent. Today, it’s 40 percent.

  Christakis said in a Wired article that what happened was that social norms on diet changed. “A bunch of people discovered fast food at the same time and the social network took over.”

  According to the study, having an obese spouse raises the risk of becoming obese by 37 percent, having an obese friend raises it to 171 percent. The study showed that social networks are better at predicting obesity rather than the presence of so-alled “fat genes.”

• Smokers quit together
  According to the study, 65 percent of Framingham residents aged 40 to 49 smoked regularly in 1971. By 2001, only 22 percent smoked.

  In 1971, smokers and non-smokers intermingled freely and many of the towns heavy smokers had plenty of nonsmoking friends. In 2001, groups of smokers were socially isolated. Entire groups of smokers quit in unison.

  The study also found that when smokers quit, their friends were 36 percent likely to follow.

• Happiness is contagious offline and on the Internet
  A happy friend increases an individual’s probability of being happy by 9 percent. In contrast, an extra $5,000 income only raises it by 2 percent. Even friends of friends have a positive influence on one’s happiness, the study said.

  Christakis and Fowler also studied Facebook pages of students in one university and found that people who smiled in their profile photos tended to cluster with other people who also smiled. They also found that smiling Facebook members have 15 percent more close friends than their dour peers.

The study tells us that social behavior, whether good or bad, spreads through our network. What our friends and family members do influence our own behavior.

And that’s how running spreads like a virus—a particularly potent one. You see it every Sunday in the city’s streets. I saw it last night in Ayala Center Cebu, where close to 400 people ran the 8th staging of the Midnight Run. More and more people are running.

If someone starts running in an office and keeps at it, you can bet your Newton Running Shoes a colleague will eventually start running also. Runners constantly talking about their sport, posting photos of running events and writing about how much running has improved their lives can spread the running virus in social networks like Facebook and Twitter.

The sport’s social network super-connectors like John Pages, Raffy Uytiepo and Dr. Potenciano “Yong” Larrazabal III have influenced hundreds if not thousands in Cebu to start running. These runners, in turn, influence their colleagues and family members to take up the sport.

That’s why more and more people are running. Happy people are taking over the city’s roads.