Obesity (a body mass index (BMI) of 30 or more) and overweight (a BMI of 25–29.9) are associated with reduced fertility in both women and men. In women, obesity may lead to infertility due to ovulation disorders, irregular menstrual cycles, or an increased risk of problems during pregnancy, such as miscarriages or delivery complications that have lasting effects on children. The reason behind reduced fertility in overweight women is that excess weight causes changes in the functioning of reproductive tissues, the ovaries, the uterus, and brain regions that secrete sex hormones. Studies have shown that the average time to pregnancy is longer in obese women than in “normal weight” women. Thus, you can improve your odds of getting pregnant by losing weight in a safe, controlled manner. Crash diets are not recommended, because your body needs to have an adequate supply of vitamins and nutrients to support conception. Women can increase their odds of getting pregnant by maintaining a healthy diet (specifically, by reducing consumption of sugar and other carbohydrates), getting plenty of physical activity, and using nutritional supplements that support safe pregnancy and embryo development.
Obesity also reduces the chances of getting pregnant for women who use assisted reproductive technologies such as in vitro fertilization. In addition, obese or overweight women who successfully conceive through in vitro fertilization face a greater risk of miscarriage.