Marriage and divorce are both "weight shocks" that can cause men and women to gain or lose weight, according to a new study by Ohio State researchers. But a closer look found the risk of extreme weight gain (21 pounds or more) was greater for women within two years of marriage, and greater for men within two years of divorce.

The study results, released today, didn't examine the underlying reasons for these trends, but the authors believe the traditional household roles for women may be at work in both cases.

"Married women often have a larger role around the house than men do, and they may have less time to exercise and stay fit than similar unmarried women," said co-author Zhenchao Qian, whose study was presented this weekend at the annual conference of the American Sociological Association. "On the other hand, studies show that married men get a health benefit from marriage, and they lose that benefit once they get divorced, which may lead to their weight gain."

Age was significant. Marriage and divorce didn't have as much of an impact on men or women in their 20s. But these major life events were more likely to cause weight gain for people 30 and older. Older men might be set in their ways, and struggle to adjust to new responsibilities and lifestyles after their divorces,

"As you get older, having a sudden change in your life like a marriage or a divorce is a bigger shock than it would have been when you were younger, and that can really impact your weight," said the other co-author, Dmitry Tumin.

Most studies show that divorcees tend to lose weight, but the authors said those studies looked at broad averages and didn't separate demographic groups by gender and age.

The new study was based on responses of more than 10,000 people to the National Longitudinal Survey of Youth, a nationally representative sample of men and women aged 14 to 22 in 1979. The study has limitations, including that it couldn't determine whether people's eating habits immediately before their marriages or divorces were already setting them on paths for weight change. The study only looked at weight change two years after a marital transition, so it's unclear whether people continue to lose or gain weight following marriage or divorce.