Recent research shows that being overweight can have a negative impact on your fertility. This has been proven scientifically for women and there are some indications that it is also true for men.
Overweight and obese women are respectively 1.3 and 2.7 times more likely to have anovulatory infertility. 75 percent of women who have anovulatory infertility suffer from polycystic ovary syndrome (PCOS). The main cause of this disease is insulin resistance, a metabolic disturbance in which the body does not react to insulin. Insulin resistance is present in 50 to 80 percent of all women who have PCOS. Half of these women are obese.Insulin normally stimulates the secretion of LH, luteinizing hormone, which induces ovulation. However, if there is insulin resistance, ovulation is less likely to occur. Also, women with PCOS often have androgen and leptin levels that are too high and sex hormone-binding globulin levels that are too low.

Obesity in women also reduces the effectiveness of hormone treatments for anovulatory infertility. When insulin resistance is present, higher gonadotropin levels are needed to induce ovulation. Compared to healthy women, obese women who undergo low-dose gonadotropin therapy have lower pregnancy rates and higher miscarriage rates.

This process can be reversed in as little as six months. Weight loss of only 5 to 10 percent total body mass can be enough to restore fertility in 55 to 100 percent of obese women. A healthier weight causes the body to become reactive to insulin again. Normalized LH levels improve ovarian functions and regular ovulations recommence.

Overweight men have 11 percent more chance of having a lower sperm count than normal-weight men and 39 percent more chance of having no sperm at all. For obese men, these percentages are respectively 42 and 81 percent. Although this is not definite proof that excess weight reduces men’s fertility, it does make it more likely that overweight and obese men could have more difficulties with conception.

Since there is a clear connection between excess weight and PCOS in women, losing weight should be the first step in treating fertility problems. It is proven effective and promotes overall health. Also, since hormone treatments are significantly less effective in obese women, it makes sense to first focus on losing weight before considering these treatments. For men, carrying extra pounds is potentially related to lower sperm counts and difficulties with conception. However, more scientific studies are needed to confirm this hypothesis.