Women with higher waist circumference are more likely to struggle with fertility, a study finds. However, engaging in physical activity may be protective against infertility, especially in women with larger waist sizes.
Infertility, when a pregnancy cannot be achieved for a year or longer, affects about one in four couples in the developed world. In the United States, some 6.1 million women, or about 10% of the reproductive-age population, struggle with getting pregnant.
Previous research has associated obesity with infertility, but the findings were inconclusive. Moreover, it mainly focused on the body mass index (BMI), which is not a very accurate measure of obesity.
A new study that appeared in PLOS One suggests that waist circumference (WC) rather than BMI can explain the link between obesity and female infertility. The study found that for every 1 cm (0.39 in) increase in waist circumference, the risk of infertility rose by 3%.
The study used data from 3,239 female participants aged 18 to 45 from the National Health and Nutrition Examination Survey. Of these women, 327 (11.1%) were infertile.
Infertile participants had a higher waist circumference than fertile ones (102.8 cm vs. 93.7 cm, respectively) and higher BMI (32.0 vs. 28.7). They were also older, had better education, were more likely to have a regular partner, and had ever been pregnant. Conditions like hypertension and diabetes were also more common among infertile women.
The participants were divided into five groups according to the size of their waist circumference. Those with the biggest WC (between 109.3 and 172.5 cm) had a 2.64 higher risk of infertility than the participants in the group with the lowest waist circumference between 56.4 and 77.8.
Engaging in moderate recreational activities was found to reduce the risk of WC-related infertility, especially when the waist circumference was larger than 113.5 cm.
Adults need 150 minutes of moderate-intensity physical activity and two days of muscle-strengthening activity per week to maintain health, according to the Physical Activity Guidelines for Americans.
The study, however, does not prove that having a high waist circumference increases infertility risk; it just shows an association.
Moreover, the study has several limitations. Because infertility was self-reported, the participants may have had difficulty recalling how long exactly they struggled with conceiving. The findings may not be generalized to other countries, as the study used data from the U.S.
The link between obesity and infertility
The exact mechanisms explaining the link between obesity and female fertility remain unclear.
Previous research has associated obesity with changes in hormonal profiles, including excessive secretion of insulin and estrogen and decreased levels of anti-inflammatory hormone adiponectin and sex-hormone binding globulin.
Insulin resistance, commonly linked to obesity, may also play a role, as it can exacerbate hormonal imbalance and ovulation disorder.
Obese individuals often experience chronic inflammation and oxidative stress, which may further exacerbate these effects by promoting insulin resistance, disrupting ovarian function, and impairing embryo implantation.
And it’s not just that obesity affects female fertility only. Overweight and obese men are more likely to have low or nonexistent sperm counts compared to men of normal weight, according to a 2012 study.
More research is needed to determine the exact role high waist circumference plays in obesity. Meanwhile, maintaining a healthy weight can prevent many other serious conditions and premature death.
- PLOS One. Association between waist circumference and female infertility in the United States.
- U.S. Department of Health and Human Services. Physical Activity Guidelines for Americans.
- JAMA Internal Medicine. Obesity and Increased Risk for Oligozoospermia and Azoospermia.