Women who have their ovaries and uterus removed - to treat fibroids, for example - tend to gain more weight in the years afterward than those who only have their uterus taken out or don't have surgery at all, a new study hints.
The findings suggest that surgery to remove the uterus, called a hysterectomy, doesn't have much effect on weight on its own - contrary to what many women may believe, according to Patricia Moorman, a women's health researcher at Duke University Medical Center in Durham, North Carolina.
"It's encouraging in that respect," added Moorman, who wasn't involved in the new study.
About 600,000 women in the U.S. have a hysterectomy each year.
Some earlier research had shown women who have their uterus removed tend to be heavier than those who don't have the surgery - but the studies could not say whether they were also heavier to begin with.
For the current study, researchers tracked women for up to 10 years, beginning before menopause and ending after natural menopause or surgery.
The women were in their 40s or early 50s at the start of the study, conducted at sites across the United States.
Most of the women - 1,780 out of 1,962 - did not have surgery and went through menopause naturally.
Among those who had surgery to remove their uterus, 76 kept their ovaries and 106 had both of their ovaries removed, which is done to prevent ovarian cancer.
Women who ended up having a hysterectomy started out the study heavier, on average, than those who went through natural menopause. That difference was about two points on a body mass index (BMI) scale - equal to about 10 pounds.
Carolyn Gibson, the lead author of the study and a graduate student at the University of Pittsburgh, said conditions that lead to hysterectomy - such as endometriosis and uterine fibroids - are linked with higher weight, which might explain why the surgery groups were heavier to begin with.
Over time, women in all three groups tended to gain weight. And the women who had a hysterectomy with ovary removal put on more pounds than those who didn't have surgery or only had their uterus out, the researchers reported in the International Journal of Obesity.
Women who had a hysterectomy and ovary removal gained 0.21 BMI points each year after surgery - equal to about one pound, depending on a woman's exact height and weight. Those who didn't have surgery gained 0.08 BMI points each year post-menopause, on average.
Changes in hormone production after surgery probably explain the findings, said Gibson, although her study can't prove that's the case.
Women who go through menopause naturally experience a gradual drop in hormones, whereas ovary removal causes an abrupt halt to some hormone production.
Moorman said she would be cautious about making too many conclusions based on the findings because so few women in the study had their ovaries removed compared to the large majority of women who did not have surgery.
Gibson pointed out that the differences between the groups were slight, but that a potential increase in weight gain should be something women and their doctors consider when deciding whether to remove the ovaries, given the link between higher weight and chronic health problems.
"It's often done to decrease the risk of ovarian cancer, which is of course a very serious consideration," she told Reuters Health. "That said, if it is conferring risk for other chronic diseases that might have health consequences for women down the road, I think it's certainly something to take into account."