Your marriage has a lot more to do with your fitness profile than you might think. Public health researchers at John Hopkins University recently studied the love and health lives of middle aged men and found that out of about 55 percent of men who don't meet the American Heart Association's recommendations for staying active (that's 75 to 150 minutes of exercise per week), 70 percent were more likely to report exercising on following doctor's visits if their wife had a similar fitness regime.
The influence also extended to smoking: If one half of a couple quit the habit, the other was more likely to give up too. The researchers had analyzed the medical records and relationship statuses of nearly 16,000 people, and followed up with individuals about activity levels over six years.
But while this and previous studies might suggest having a life partner can be good for your overall health (including living longer), just being in a relationship isn't enough. Who you settle down with matters more, since it's important to note instances where marriages can ruin your health. "Spouses change in the same direction, meaning that if a spouse increases their physical activity, then an individual is more likely to increase their own physical activity — but also that if the spouse becomes less physically active, the individual is also more likely to reduce their physical activity," says Laura Cobb, co-author of the study. She adds that another study from the University of North Carolina tracking over 7,000 people over six years found that individuals had a higher risk of developing obesity when married or living together than when single.
Having a significant other isn't the only kind of relationship influencing your health: Research also shows the platonic people you surround yourself with — whether it's your friends, work colleagues or roommates — can be equally (if not more) telling. A study in the New England Journal of Medicine analyzed the data of a social network of about 12,000 people (consisting of friends, relatives, siblings, parents, etc) over 32 years and noticed that instances of obesity kept occurring in clusters of the densely interconnected people — with up to three degrees of separation. If one individual were to become obese, their friend was more than twice as likely to become obese too — about 57 percent more likely, that is.
Of course Cobb's study and others have limitations: While it's most likely that people are directly affecting each other's habits, it could also be that individuals marry and befriend those with similar habits to begin with. But that still doesn't undermine the importance of being careful who you hang with. And Cobb has other theories: spouses (and often friends) share the same physical environment, so they're subject to the same influences. Spouses might also simply "converge" over time, she says, changing to be more like the other. Whatever the explanation, the advice is simple: choose your friends wisely.