The societal pressures on women to be attractive, successful, and thin are stronger than ever. The desirable woman portrayed in the media is much thinner than the average woman. Popular slogans such as "thin is in" and "you can never be too rich or too thin" have equated thinness with happiness. The result is that for the first time in history, being attractive means being thin.
Healthy weight women have an easier time getting pregnant than overweight or underweight women. Studies show that women whose body mass index (BMI) is below 20 or above 25 (especially above 30) have a harder time getting pregnant, so it's a good idea to try to get yourself into the 20 to 25 range before you start trying.
According to Dr. Fady Sharara, board-certified reproductive endocrinologist and Medical Director of the Virginia Center for Reproductive Medicine, being underweight can affect a woman’s fertility, due to reduced body fat that can affect ovulation. “Even moderate weight loss of 10-15% under the ideal body weight can result in an irregular menstrual cycle,” says Dr. Sharara. This contradicts the popular belief that only dramatic weight loss of 30% or more-commonly found in women with anorexia nervosa and bulimia-will lead to menstrual irregularities. Studies show that up to 73 percent of these underweight women who have been able to achieve 95 percent of their ideal body weight, have restored ovulation and pregnancy.
In addition, obesity and weight gain are also emerging as significant factors in ovulatory dysfunction and thus infertility. More than 60% of the US population is overweight (BMI > 25), and at least 30% are obese (BMI > 30). Polycystic Ovarian Syndrome (PCOS), which is a health problem that can affect a woman’s menstrual cycle and fertility, has been linked to weight gain or obesity. However, women who do not have PCOS but are overweight have also been linked to fertility problems. “The insulin resistance state induced by the weight gain results in an altered hormonal milieu, which can impair the fertility process”, says Dr. Sharara. “In addition to being infertile, these women have also increased risk at developing diabetes, high blood pressure, and heart disease as they get older.” Many overweight women who have gone through group treatment programs to lose weight have shown a return of fertility. Also, studies have shown that weight loss of 15 pounds can restore ovulation in women who are overweight (obese women need to lose more). Many researchers believe that the body’s ability to regulate insulin production has more to do with the regulation of ovulation than the weight loss itself. Being overweight or obese result in significantly reduced chances at getting pregnant with fertility treatments such as IVF, which was shown by Dr Sharara in 2001, and recently confirmed in larger studies.
Dr. Sharara advises infertile couples to consider body weight first. Weight gain is the first treatment he recommends to women who weigh less than 95 percent of their ideal body weight. Conversely, he advises women who weigh more than 120 percent of their ideal body weight, to lose weight.