The Skinny on the Impact of Weight and Fitness on Fertility

When a couple is trying to become pregnant, maintaining a healthy lifestyle is a key component of reproductive success. Studies show that women who control their weight with diet and exercise have a greater likelihood of getting and staying pregnant. For men, the benefits of proper weight include higher sperm counts and sperm with greater motility, among other advantages. Research is ongoing to allow experts to understand the many different ways that being overweight contributes to infertility, but enough is already known to prove that the impact is substantial.

Obesity and Infertility in Women

Research published in Fertility and Sterility, a journal of the American Society for Reproductive Medicine, describes how women who are overweight have poorer outcomes than women of normal or even below normal weight in areas related to:

  • Implantation rate
  • Establishing clinical pregnancy
  • Maintaining pregnancy
  • Live birth

How does being overweight impact fertility in women? The extra fat cells are linked with hormone imbalance such as the ratio estrogen to androgen that can adversely impact fertility potential. The increase in androgen levels contributes to issues such as menstrual irregularities, miscarriages, and birth complications.

Austin female fertility expert Dr. Shahryar Kavoussi explains that obesity can even lead to issues such as polycystic ovary syndrome (PCOS), where women suffer from infrequent or even the absence of menstrual periods. PCOS inhibits or sometimes prevents normal ovulation, reducing opportunities for pregnancy in roughly 10% of women during their reproductive years. Women with PCOS also can have increased insulin levels, which raise androgen levels and compounds hormone imbalance further.

By becoming more fit with proper exercise and diet to lose weight, women with PCOS can improve their chances of fertility success. By losing weight, insulin levels will decrease thereby bringing androgen levels back to normal, which can reverse fertility issues.

Although women who experience even moderate weight loss reportedly see subsequent improvements in fertility, rapid or extreme weight fluctuation is not advised as this can negatively impact fertility. A sensible lifestyle habit and approach to weight control through moderate exercise and a healthy diet offers the best support for reproductive success.

Obesity and Infertility in Men

Women are not alone in needing to manage their weight for optimal fertility, as approximately 60% of infertility issues are attributed to the male partner contributing to subfertility, with obesity being a major factor. Men with extra body weight suffer more frequently from conditions that can adversely affect male fertility including lowered sperm quality and quantity, impaired sperm motility, DNA damaged sperms, and low testosterone.

Low testosterone is linked with a host of sexual and other health issues for men. Testosterone is an important hormone regulating sperm production and function. In relation to fitness, overweight men with low testosterone are caught in a cycle where more fat cells lead to more testosterone being converted into estrogen. Aromatase, an enzyme in fat cells, changes testosterone into estrogen. With less testosterone, it is more difficult to decrease fat and retain muscle mass. It is advised not to take testosterone supplements as that can have negative effects on fertility. Instead, it is recommended that men incorporate exercise and diet to burn fat which breaks the cycle of testosterone to estrogen conversion and thereby help preserve testosterone.

Some data indicate that infertile men who are heavier are also affected by non-obstructive azoospermia, which is a condition in where there is no sperm in the semen caused by the lack of sperm production.

According to reproductive urologist and male fertility specialist Dr. Parviz Kavoussi, men who are overweight have more fat around the scrotum that can adversely impact sperm production in the testicles. This fat increases heat to the area, which is damaging to sperm, as sperm requires a temperature that is a few degrees cooler than the overall body temperature in order to thrive.

By understanding how obesity impacts male fertility, men who are overweight can be more proactive in combating obesity and increasing their chances in fathering.

It Takes Two

Although the ideal body mass index (BMI) isn’t perfectly defined, maintaining a BMI of 30 or less is optimal for both women and men for fertility. However, fitness and managing weight is only one part of the equation. For a couple with fertility challenges, experts caution that there are many factors impacting a successful pregnancy such as ovulation, tubal, uterine, peritoneal, and male factors that can have more profound effects on a couple’s fertility. From ovulation to fertilization, implantation to supportive pregnancy hormones, each phase has its own variables.


Decreasing health-related issues and living healthier prior to initiating fertility treatments will enhance the chances for a positive outcome. Perhaps most important is working with both male and female reproductive experts simultaneously to address potential issues as a team.