Most people understand that having extra weight can harm their overall health. Still, you may not know that being overweight or obese can also have an adverse impact on fertility for both men and women. This correlation between weight and fertility issues is vital to understand, with a reported 17.5% of the adult population experiencing infertility, according to the World Health Organization.

Weight and fertility in women

Infertility is the failure to achieve clinical pregnancy after 12 months or more of regular, unprotected sexual intercourse. Those experiencing infertility can experience significant anxiety, financial hardship and more. Consequently, when health care providers tell heavier people they’re struggling with fertility because of their weight, it’s vital to understand why this is and what you can do about it, says bariatric surgeon Corrigan McBride, MD.

In those assigned female at birth, several weight-related conditions can negatively affect fertility, including:

• Polycystic ovary syndrome (PCOS)
• Ovulation dysfunction
• Peritoneal and tubal factors
• Endometriosis

Each of these conditions can reduce your chances of getting or staying pregnant. For example, PCOS – the most common endocrine problem for women between 18 and 50 – prevents women from ovulating or passing an egg each month and produces excess testosterone in their body, both increasing infertility. Additionally, PCOS can cause:

• Menstrual irregularities (not having a period every month).
• Lower egg quality.
• Lower egg quantity.
• Longer time to conception.
• Increase medication dosages to simulate ovulation (if using assisted reproductive technology – ART).

Weight and fertility in men

Although those assigned male at birth aren’t responsible for birthing a baby, they are half of the necessary equation for making one. Accordingly, weight can impact infertility in men, too. Obesity in men hurts:

• Semen quality.
• Sperm integrity (how long they live).

These characteristics result in fewer conceptions and live birth rates for their partners (both natural and those using ART).

Bariatric surgery and fertility

Thankfully, for those struggling with weight-related infertility, there are effective treatment options. “There is good data that losing 5% to 10% of your body weight through medical means can improve fertility,” says Dr. McBride. One specific treatment with studied positive results is bariatric surgery. 

Bariatric surgery, also called metabolic or weight loss surgery, is a surgical operation to assist patients in losing weight. Types of bariatric surgeries include:

• Gastric bypass
• Sleeve gastrectomy
• Duodenal switch

One large study of female patients who underwent bariatric surgery reported:

• An improved sexual function scale.
• Improvement in the sex hormones that are part of ovulation and a regular menstruation cycle.
• Decreased menstrual irregularity at six months. 

For women with PCOS, specifically, bariatric surgery can also result in:

• Significant weight loss, especially for those with central obesity – (also called abdominal obesity) or excess fat in the area between your chest and pelvis.
• Lower testosterone levels.
• Improved blood sugar control.
• Significant improvement in high blood pressure.
• Normalization of menstrual cycle.

The same study analyzing the effects of bariatric surgery on fertility in women also found some positive results for men’s fertility. Men in the study reported that bariatric surgery improved erectile dysfunction scores after 12 months and the production of male sex hormones that affect sperm and semen production.

Bariatric surgery and pregnancy

In addition to aiding fertility in both men and women, bariatric surgery has also been shown to have a positive impact on those who become pregnant after the procedure. Post-bariatric surgery patients who became pregnant had:

• Lower risk of developing gestational diabetes.
• Fewer cases of having a large-for-gestational-age baby. 
• A slightly higher chance of having a small-for-gestational-age baby.
• No difference in the risk of pre-term birth.
• Lower risk of needing a Cesarean section.