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Obesity and Infertility

Decreased fertility due to obesity may be a problem for more than just moms. An NIH study found that couples in which both partners are considered obese may experience more difficulty conceiving than those in which only one is considered obese. 

The study confirms what others have shown: Women who are considered obese (BMI over 30) have lower fertility. However, it also finds that this effect is significantly increased when both members of a couple are obese.

Couples in which both members have a BMI over 35 experience 60% lower fecundity than couples in which both partners have a BMI under 25, which is considered healthy.

“Obesity has negative effects on both men and women,” said Erica Johnstone, MD, a gynecologist and reproductive endocrinologist with University of Utah Health. “In women, obesity can lead to irregular periods and poorer egg quality as well as decreased chances of success with fertility treatments. In men, excess weight can cause decreased testosterone levels, causing men to feel tired and lose their libido. Obesity can also cause decreased sperm production.”

Even though fertility treatments may increase fertility, they are still less effective for obese couples.

The NIH study is one of the first controlled studies to use both female and male body composition when reviewing fecundity. The study followed 500 couples in Texas and Michigan as they tried to conceive. Fertility was tracked over the course of a year for each couple and was measured by the amount of time spent trying to conceive before becoming pregnant. 27% of women and 41% of men in the study had a BMI above 30.

More than 36% of adult Americans are considered obese, a number that has been growing steadily over the past 20 years, according to the CDC, so the problem of reduced fertility due to body composition may be growing in the population.

However, increasing fertility may be possible for many couples incorporating a few lifestyle changes.

“Losing 5-10% of body weight can improve ovulation and fertility as well as provide other health benefits,” said Johnstone. “In addition to eating a healthy, balanced diet and exercising at least 30 minutes at least five days per week, couples trying to conceive should stop smoking, limit alcohol to four drinks a week or less, and sleep at least seven hours per night.”


About the author:

Emily Sundquist is an intern at the Office of Public Affairs at University of Utah Health. She is an undergraduate at Williams College studying Biology and Mathematics.

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