According to the research, being moderately overweight or underweight has little effect on fertility in either men or women. Of course, conception is best facilitated by the appropriate body weight within the BMI norms, so take some time to regulate it in the preparation for pregnancy.
The optimal parameter for fertility is a BMI between 18.5 and 24.9. Fertility disorders are observed in men and women who are severely obese (i.e., BMI > 30) or severely malnourished (BMI<15).
Significant underweight in ladies may result in hormonal disturbances and absence of menstruation. Obesity, on the other hand, can result in the production of excess male hormones, leading to ovulation disorders and thus making it difficult to get pregnant. There are reports showing that reducing body weight by even 5-10% significantly improves ovulation and pregnancy rates.
In men, on the other hand, being significantly overweight may result in a decrease in testosterone production and, consequently, impaired sperm production and reduced fertility.
Interestingly, when treating fertility disorders its effectiveness can also be linked to weight reduction in obese individuals. A study of IVF patients in Ecuador showed that obese and severely overweight women had significantly lower rates of pregnancy, implantation and live birth than women of normal weight.