Lifestyle and PCOS
In addition to the reproductive abnormalities of chronic anovulation and hyperandrogenism, a significant majority of women with PCOS are more insulin resistant than controls matched for body-mass index, fat free body mass, and body-fat distribution.
Insulin resistance (IR) is now recognised as having an integral aetiological role in PCOS. IR underlies metabolic syndrome, with all needing screening for CVRF status. IR is also a risk factor for abnormal glucose metabolism. In young, obese women with PCOS the rates of abnormal glucose tolerance are very high; 15-20% have IGT in their 20s, 30-40% have impaired glucose tolerance (IGT) and up to 10% have type 2 diabetes (DM) by their fourth decade.
Amelioration of IR occurs with weight loss in obese subjects with and without PCOS. In PCOS, the reduction in IR with weight loss results in improved androgen levels, ovulation rate, menstrual cycle regulation, and improved fertility. Others have reported symptom improvement and related this to weight loss and more specifically reduction in IR.
A number of different lifestyle strategies to reduce IR in obese women with PCOS (BMI 32-42 kg/m²) have been studied. However to date the prospective studies reported have been limited by small numbers (n=6-40), lack of controls or use of controls who had failed to finish study protocol and use of variable IR assessment tools. The evidence base is further limited by few head-to-head comparison studies, and no long-term follow-up to assess effects of short-term decreases in IR on long-term complications such as DM2 and cardiovascular risk in PCOS.
In the general population diet and exercise lead to preferential loss of visceral fat. In women with PCOS, visceral fat is highly correlated with IR and waist circumference. In PCOS, the likely means by which weight loss improves IR is through loss of visceral fat with resultant metabolic improvements.
Short-term weight loss strategies using very low calorie diets (<500kcal\day) for 4 weeks have achieved 6.6-9% loss of initial body weight and have been shown to decrease serum insulin levels13, OGTT stimulated-insulin14 and insulin sensitivity on the clamp test in patients with PCOS.
As this type of weight loss program is not viable long term, other weight loss trials have used moderate caloric restriction (1000-1500kcal/day) for 2-15 months. In these studies weight loss of as little as 5% and up to 14% has resulted in improved fasting insulin, OGTT-stimulated insulin, HOMA and insulin sensitivity on clamp testing.
Diet and Nutrition
Despite evidence in other IR populations that high protein, low carbohydrate (CHO) diets increase lean body mass and increase insulin sensitivity, in obese women with PCOS, research has shown no advantage of high versus low protein diet. It appears that caloric restriction is paramount and that no specific dietary composition can be recommended.
Weight gain and Exercise
Exercise training is a safe first line alternative in the management of IR in PCOS. Mechanistically, immediately after an acute period of exercise, glucose transport in skeletal muscle is increased through insulin-independent translocation of the GLUT4 glucose transporters to the cell membrane.23 The molecular mechanisms for enhanced insulin sensitivity with exercise training may be related to increased expression/activation of key proteins in the insulin signaling pathway that regulate glucose metabolism in skeletal muscle.
Lifestyle studies have generally focused on diet in conjunction with moderate low intensity exercise in a group environment. These studies have had high drop-out rates with difficulty in maintaining compliance. Recent studies have examined the role of exercise alone.
Results are impressive so far with reduced insulin resistance, improved ovulation, lowered androgens, improved metabolic profile and increased pregnancies. Whilst the mechanisms require further exploration, regular moderate intensity exercise is known to improve quality of life and insulin action in health and disease, including in non-obese women and diabetic men, and now appears to be beneficial in PCOS as well.