Got an overweight colleague? Friend? Family member?
Watch your waistline -- latest research suggests that obesity is contagious.
Harvard researchers working in tandem with their peers from the University of California, San Diego, say that if members in your close circle are overweight, it sends a subtle signal that such a body shape, and lifestyle, is acceptable.
The result: you are likely to put on several pounds within the next couple of years.
Simply put, say the researchers in a study widely cited in the international news media, obesity can spread through social interaction, much like flu.
The good news is that if members of your close circle are fit, you are likely to lose weight as well.
"Ours is the first study to show how obesity spreads through a social network," Dr James Fowler, a political science professor at the University of California San Diego and one of the study's two authors, is quoted as saying.
The moral, he says, is "If you want to be successful in getting your weight down, get as many of the people to whom you are socially connected involved because there will be a reinforcing effect between your behavior and theirs."
The report said a person's chance of becoming obese increases by 57 percent if he or she has a friend who became obese, 40 percent if a sibling became obese and 37 percent if a spouse became obese.
The study further says when two people named each other as friends and one of them became obese, the second person's chance of also gaining a significant amount of weight increased by 171 percent. Adjacent neighbors who weren't friends had no influence, however.
The fascinating aspect of the study is that the sway of a friend's weight change persisted even if that person moved hundreds of miles away and was only seen once or twice a year.
Among the more interesting findings in the research is that a friend's weight gain or loss will have a bigger influence than family or genetics. While weight changes in a person's family members, spouses and siblings also had an impact, the study says causal links were greatest among people who identified each other as "mutual friends."
In another finding, the researchers say this works more among people of the same sex -- that is to say, men with overweight friends were apt to gain pounds, more than if they had overweight women friends. And vice versa.
There is more bad news: the obesity virus is not just restricted to a close friend - if you are fat, it affects not just you, but also the good friend of a good friend.
The study, published this week in the New England Journal of Medicine, has been funded by the National Institute on Aging.
Researchers suggest that if the findings can be further validated, it will prompt offices, insurers, school administrators and such to promote group exercises and diets in workplaces and community settings, to combat obesity and its attendant risks such as diabetes and hypertension.