Obesity and PCOS

Obesity has a profound effect on the clinical manifestation of polycystic ovary syndrome (PCOS), a hormonal disorder affecting 20-25% of white European women and up to 50% of women in the UK from South Asia. About 50% of women with PCOS are overweight, and this increase in body weight has a major influence on the symptoms of PCOS and fertility.

This month’s edition of the BJOG journal (an international journal of obstetrics and gynaecology), produced by the Royal College of Obstetricians and Gynaecologists, documents a number of research articles on the impact of obesity on PCOS and reproductive health.

Professor Adam Balen, spokesperson for RCOG, and editor of the current issue of the BJOG journal, says: “PCOS is a major health problem affecting women of all ages. The prevalence of PCOS appears to be rising because of the current epidemic of obesity. PCOS accounts for 90-95% of women who attend infertility clinics with anovulation. Some of the symptoms such as unwanted facial and bodily hair, acne, obesity and infertility have profound effects on the quality of life for these women.”

There are a number of interlinking factors that affect expression of the syndrome. A gain in weight is associated with a worsening of symptoms whilst weight loss will improve the disease profile and its symptoms. The main clinical features are menstrual cycle disturbance and an increase in male hormones (hyperandrogenism), causing acne, unwanted bodily and facial hair, and alopecia.

Obesity has a negative impact on spontaneous conception, miscarriage, pregnancy and the long term health of both mother and child due to both an increased rate of congenital anomalies and the possibility of metabolic disease (including diabetes) in later life. In women with PCOS and a higher body mass index, 20% of pregnancies ended with stillbirth and another 20% had congenital anomalies. The supposed mechanism that increases stillbirth and congenital anomaly rate includes insulin resistance and impending or undiagnosed diabetes.

BMI is easy to measure. However, in metabolic terms, the distribution of body fat is more important than actual body weight. Visceral fat (within the abdomen) is more metabolically active, and an increased waist circumference (or waist:hip ratio) correlates better with both metabolic risk and long term disease.

Insulin resistance is also an important correlate of BMI and is perceived as a more accurate marker of the metabolic effect of obesity. There are also important ethnic variations in the expression of insulin resistance. A BMI greater than 30 kg/m2 is usually considered to confer increased risk in white Europeans whereas in women of South Asian origin a lower BMI greater than 25 kg/m2 is sufficient to cause increased risk of metabolic defects.

Several studies have shown that weight loss in women with PCOS improves the endocrine profile, menstrual cyclicity, rate of ovulation and likelihood of a healthy pregnancy. Even a modest loss of 5% - 10% of total body weight can achieve a 30% reduction of central fat, an improvement in insulin sensitivity and restore ovulation. Lifestyle modification is clearly a key component for the improvement of reproductive function for overweight, anovulatory women with PCOS.

Exercise and weight-loss have so far been the best way to improve insulin sensitivity, and improve the metabolic abnormalities associated with the syndrome. However obese women with PCOS often report extreme difficulty in loosing weight and maintaining weight loss. Weight loss interventions do not appear to be common practice among fertility centres and gynaecological clinics in spite of clear evidence as to the benefits.

For more information about PCOS, visit rcog.org.uk.