Written for Health Professionals

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.¹ Insulin resistance (IR) is now recognised as having an integral aetiological role in PCOS. IR underlies metabolic syndrome and 42% of young Australian women with PCOS have 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.^2,3 Lifestyle intervention improves insulin resistance, prevents progression to diabetes in non PCOS populations and is the accepted first line intervention in PCOS. The literature in this area is summarized below.

Non-Pharmacological Management of IR in PCOS

Weight Loss

Amelioration of IR occurs with weight loss in obese subjects with and without PCOS.⁴ In PCOS, the reduction in IR with weight loss results in improved androgen levels, ovulation rate, menstrual cycle regulation, and improved fertility.^5,6 Others have reported symptom improvement and related this to weight loss and more specifically reduction in IR.^7,8 In the general population diet and exercise lead to preferential loss of visceral fat.⁹  In women with PCOS, visceral fat is highly correlated with IR and waist circumference.^6,10  In PCOS, the likely means by which weight loss improves IR is through loss of visceral fat with resultant metabolic improvements.

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.

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^11-14 and have been shown to decrease serum insulin levels¹³, OGTT stimulated-insulin¹⁴ and insulin sensitivity on the clamp test in patients with PCOS.¹²

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.^6,15,16  In these studies weight loss of as little as 5% and up to 14% has resulted in improved fasting insulin¹⁶, OGTT-stimulated insulin¹⁵, HOMA¹⁷ and insulin sensitivity on clamp testing.⁶  Another study suggested that improvement in IR (HOMA) may be maximal in the acute catabolic phase of energy restriction rather than during weight maintenance.¹⁷

Few studies have combined energy restriction with physical activity.  More recently a 6-month lifestyle modification was performed in a group of obese anovulatory PCOS women and obese ovulatory controls.⁷  The group program included 1 hour of weekly supervised exercise with encouragement to do a further two hours per week as well as one hour of diet and lifestyle education (18).  In this study, mean weight loss was only 2-5% of body weight however 9/15 still became ovulatory.  This was associated with an improvement in insulin sensitivity of 71% using the "gold standard" euglycaemic hyperinsulinemic clamp. Significant improvements in fasting insulin, waist circumference and central abdominal fat (but not in androgen levels) were also seen in those that responded.  There was no improvement in any of these measures in non-responders who remained anovulatory.

IR and Dietary composition

Despite evidence in other IR populations that high protein, low carbohydrate (CHO) diets increase lean body mass and increase insulin sensitivity¹⁹, in obese women with PCOS, two randomised controlled trials demonstrated no advantage of high versus low protein diet on a number of outcomes including IR.^{17, 20}  Furthermore a diet high in polyunsaturated fatty acids (PUFA)  had no effect on IR but increased glucose levels.²¹  A cross-over trial in 11 obese women with PCOS compared three diets with similar energy and protein contents.²² The diet low in CHO but high in PUFA, reduced fasting and post-challenge insulin levels on IVGTT, but not insulin sensitivity when compared with a standard diet high in monounsaturated fats (MUFA).  It appears that caloric restriction is paramount and that no specific dietary composition can be recommended.

IR 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.^24,25

Lifestyle studies to date 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 women²⁶ and diabetic men²⁷, and now appears to be beneficial in PCOS as well. 

Lifestyle intervention remains first line treatment in POCS. To achieve effective lifestyle change, low self-esteem, demoralization, guilt and body image as well as readiness to change need to be addressed and psychological counseling can be useful preceding direct lifestyle strategies. There are still research questions to be answered especially on the role of exercise and behavioural strategies to improve the feasibility and sustainability of lifestyle change. In the interim it should be remembered that realistic achievable goals (5-10% weight loss) are important to focus on and have proven health benefits.

References 

Content updated 20 November, 2009