Being overweight or obese may reduce a woman’s fertility due to irregular or infrequent menstrual cycles

Obesity may also cause an increased risk of miscarriage and decreased success with fertility treatments. When pregnancy is achieved, women with excessive weight increase their risks associated with pregnancy, such as high blood pressure, gestational diabetes, birth defects, high birth-weight infants and an increased risk of Cesarean section. Weight loss may improve fertility and pregnancy outcome. A body mass index (BMI) of 25 to 29.9 is considered overweight, and obesity is defined as a BMI of 30 and above. Weight loss of 5% to 10% may dramatically improve ovulation and pregnancy rates.

Adversely, patients who are underweight can also have problems achieving pregnancy. Underweight women are unable to produce the necessary hormones to trigger ovulation, which is essential for conception. Eating disorders, such as anorexia and bulimia, can also lead to abnormal menstrual cycles and infertility. Low body fat percentages, common in female athletes, can interfere with ovulation and cause irregular periods or no period at all. It is not uncommon for dancers, professional athletes and runners to have ovulation problems.

Weight may also be a fertility issue for men

Obesity may impair hormonal levels and adversely affect fertility in men as well. A recent Harvard study finds that overweight and obese men are more likely than their normal-weight peers to produce lower numbers of sperm, or even no sperm at all. This could increase the likelihood that they would have difficulty conceiving. While the results don’t prove that excess weight leads to fertility troubles, having a lower sperm count can make it more difficult for men to conceive. Fortunately, your weight is typically one fertility risk factor that you can change.