Women who experience infertility are often told to lose weight. A wannabe mom's extra pounds have long been the go-to culprit for any difficulties she may experience in trying to conceive (not to mention her efforts to carry out a healthy pregnancy, or to labor and give birth with minimal intervention).
But the National Institutes of Health "Longitudinal Investigation of Fertility and the Environment (LIFE) Study," published in the journal Human Reproduction, found that while a woman's obesity appears to play a role her chances of becoming pregnant, her partner's size also matters.
Couples who are obese are about half as likely to conceive in a given ovulation cycle—known as fecundability—as couples with what is considered a normal body mass index.
"Overall, obese couples were found to have approximately half the fecundability as couples with normal BMI," Rajeshwari Sundaram of the National Institute of Child Health and Human Development and colleagues wrote in their report.
Researchers came to this conclusion after following 500 Michigan and Texas couples daily for one year over four years starting in 2005. The women ranged from 18 to 44 years old, and all the men were older than 18. The women kept journals where they recorded their monthly menstrual cycles, each time they had sex and the results of pregnancy tests. Researchers followed the couples until a positive pregnancy test or for up to one year of trying to conceive.
Among the group of participants, 27 percent of the women and 41 percent of the men had BMIs that categorized them as obese. What the statisticians found was that if the woman in a pair was overweight or obese, it took longer to conceive than other couples where both the man and the woman had what was considered a normal weight. Where things got interesting was when the man and the woman were even more than overweight or obese—with BMIs of 35 or higher. These couples were found to be 60 percent less fecund—able to conceive—than their slimmer counterparts.
The health researchers stopped short of saying what exactly about obesity and morbid obesity brings on the challenges to getting pregnant. The "LIFE" Study was originally intended to look at the impacts, if any, of exposure to certain chemicals in the environment and lifestyle chemicals (like smoke) had on fertility.
That said, health experts frequenty note that obese people can have higher levels of inflammation in their bodies, which may interfere with reproduction. Also, fat cells produce hormones, which can interfere with the cocktail of hormones necessary to make conception possible.
The rate of obesity and morbid obesity is climbing in the U.S, despite efforts to slow it down and reverse it. It is predicted to hit somewhere between 42 and 44 percent among Americans by 2030. In 2014, 35 percent of U.S. men and 40 percent of women were obese.