Diet Impacts Fertility in Patients who are Overweight and have Polycystic Ovarian Syndrome

A new study published in the October issue of the Journal of Clinical Endocrinology and Metabolism (1) confirms that: “diet is an effective, acceptable, and safe intervention for relieving insulin resistance ….” Why is this so significant? Because insulin resistance is a primary factor in the cause of polycystic ovarian syndrome (PCOS).

PCOS is a metabolic disease in women which impacts multiple systems. At its core, PCOS is a syndrome of increased intra-ovarian androgens. The pathway to that endpoint and the clinical manifestations of the result are very diverse but insulin resistance is a key road on that path.

Insulin resistance is simply when insulin becomes less effective in controlling blood glucose (sugar) levels. Usually, to maintain a normal glucose level, the body releases more insulin. This response is fine for the control of the blood sugar – but not so good for the ovary. Increased insulin causes the ovary to make increased amounts of testosterone, which may affect the development of the egg. Testosterone is also released into the blood stream where it is converted by adipose (fat) tissue into estrogen which interferes with the normal hormonal control of the menstrual cycles – leading to irregular menstrual cycles. So, eggs and cycles are not optimal for fertility. In addition, the altered hormonal pattern can affect the lining of the uterus (endometrium), such that the time when the endometrium is able to accept an embryo (implantation window) can be altered.

Finally, the increased amount of androgen released by the ovary may cause an increase in a woman’s inflammatory status. This is significant for late-onset disease complications such as the cardio-vascular risk from PCOS. For the infertile woman, the increased inflammatory state may also raise the risk that an embryo will not implant or increase the miscarriage rate.
Insulin resistance is directly related to obesity. Obesity reduces a woman’s chance to have a child in a direct relationship to the BMI. Simply, the greater the BMI, the lower the overall chance to have a child.

Obesity Takes It’s Toll

Obesity is a major health risk that is increasing in frequency. It is associated with several adverse health risks such as adult- onset diabetes, cardio- vascular disease, and hypertension. In the US today, over 25% of women in the reproductive age are obese and in Mexico, that number is closer to 50%. Considering how frequently obesity occurs and the serious health consequences of being obese, it is surprising (and for those of us with weight-control issues, it is infuriating) that there are no successful long-term treatments for obesity. So, who is considered “obese?” Obesity is an excess body weight for a given height. Body mass index (BMI) is the most frequently measurement used to define obesity. A BMI (Weight in kg/ height in m2) of over 25 is considered overweight, over 30 -34 obese class 1, 35-39 obese class 2, and > 39 as obese class 3 (sometimes referred to a morbidly obese). A 5’5” woman weighing 130 pounds has a BMI of 21.6. A woman of the same height weighing 150 has a BMI of 25 and is considered overweight.

The recently published study demonstrated that diet was significantly related to improvements in insulin resistance. Arguably, improving insulin resistance could reduce intra-ovarian androgens.  This may create a more normal physiology, which could significantly improve pregnancy rates.

1)Yujie Shang, Huifang Zhou, Minghui Hu, Hua Feng, Effect of Diet on Insulin Resistance in Polycystic Ovary Syndrome, The Journal of Clinical Endocrinology & Metabolism, Volume 105, Issue 10, October 2020, Pages 3346–3360,
(2)Espinós JJ, Polo A, Sánchez-Hernández J, Bordas R, Pares P, Martínez O & Calaf J. Weight decrease improves live birth rates in obese women undergoing IVF: a pilot study. Reproductive BioMedicine Online 2017 35 417–424. rbmo.2017.06.019 10

Dr. John Rinehart MD, Ph.D. has been trained in both reproductive endocrinology and andrology at Brigham and Women’s Hospital of the Harvard Medical School. Dr. Rinehart is accepting new patients in his practices at the Oak Lawn (630-366-5100) and Hinsdale (630-366-5100) offices.