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A new study, soon to be published in the Journal of Women’s Health, provides fresh evidence that people who stay single instead of getting married, or who get instead of staying married, are especially likely to be healthy.

researchers have been insisting for decades that married people are healthier, and that they are healthier because they are married. If that were true, then people who get married should become healthier than they were when they were single, and people who get divorced should become less healthy than they were when they were married. Individual social scientists have sometimes suggested that the evidence is far from definitive (for example, in Singled Out, and later in Marriage vs. Single Life: How Science and the Media Got It So Wrong), but their objections have done little to put a dent in the prevailing assumptions. The belief that marriage is protective of health goes mostly unquestioned.

In the new study, more than 79,000 women were studied over a three-year period as they stayed unmarried; got married or entered a relationship that was like marriage; stayed married; or got divorced or separated. These women were between the ages of 50 and 79, recruited from 40 places across the U.S. They were all post- . Women who had become widowed were not included.

Many studies of health rely on participants’ own reports of how healthy they are. In this study, actual physical measurements of blood pressure, waist circumference, and BMI (body mass index) were taken by trained professionals. Those measures were supplemented by participants’ reports of their drinking, , exercising, and eating habits.

Here’s what changed when unmarried women (whether divorced, separated, or always single) got married:

After they got married, their BMI (body mass index) increased.

After they got married, they drank more.

After they got married, their systolic blood pressure increased.

Diastolic blood pressure decreased over the three-year period for those who stayed single and those who married, but it decreased less in those who got married.

Here’s what changed when married women got divorced or separated, compared to the women who stayed married:

BMI (body mass index) decreased for the women who got divorced.

Waist size decreased for the women who got divorced.

Diastolic blood pressure decreased more for the women who got divorced. (The results for systolic blood pressure showed the same pattern, but were not statistically significant.)

Improvements in healthy eating were greater for the women who got divorced.

Physical activity increased for the women who got divorced.

Among those who were not smoking at the beginning of the study, women who got divorced were more likely to start. (Among those who were already smoking at the start of the study, those who divorced were no more or less likely to stop smoking than those who stayed married.)

In summary, with just one exception, every difference in physical health favored people who stayed single (instead of getting married) and those who got divorced (instead of staying married).

To explain why women who get married get heavier, the authors reached for an explanation that has been offered in the past, although never tested: Married people regularly sit down together to share their meals, and maybe they eat larger portions because of that. The authors offered no ideas as to why the women who stayed single stayed slimmer, drank less, and had lower blood pressure than those who got married. One possibility is that single people care more about their health (and not just because they want to attract a romantic partner) and that they have more opportunities to pursue the health-affirming lifestyle they value.

The authors wondered whether the weight loss shown by women who got divorced could have been a result of and emotional upheaval, rather than any deliberate attempts to live a healthier life. They measured the women’s emotional well-being, social functioning, and levels of , but when they took those factors into account in their analyses, nothing changed. The improvements in health apparently were not just a happy accident of feeling miserable. Instead, the authors suggested, these women, who exercised more and ate better, “were actively engaged in improving their health.”

This study included only older women. But social scientists who reviewed 20 other articles on marital transitions and health–articles describing studies that included men and women of all ages–found the same thing: “Overall, transitions into marriage were associated with weight gain, whereas transitions out of marriage were associated with weight loss.”

Marriage researchers who have claimed that getting married makes people healthier have suggested various explanations for their expected results. For example, spouses supposedly monitor each other’s behavior to make sure they eat healthy, exercise, and avoid risky behavior such as drinking or taking drugs. Researchers also point to the affection and social support spouses offer each other, and suggest that such “there for you” qualities of marriage should also result in greater health among those who get married, and worse health for those who get divorced. But in this study, and in the 20 articles reviewed previously, as well as in other research described in Singled Out and Marriage vs. Single Life, that’s just not what is happening. Social scientists need to turn their to a question that—with few exceptions—they have ignored: Why is it that single people are doing so well?