PCOS affects ~10% of women of reproductive age and is characterised by hyperandrogenism and ovulatory dysfunction. About 60% of women with PCOS are overweight, with an increased risk of developing type 2 diabetes mellitus.
This Local Ethics Committee approved study aimed to determine the optimum composition of a weight reducing diet in management of women with PCOS. It compared the effect of a low carbohydrate with that of a low glycaemic index (GI) diet on anthropometric and biochemical parameters of overweight women with PCOS.
Twenty-four women not on oral contraceptives or antiandrogens were recruited to the 6-month study and randomised to a low carbohydrate diet or a low GI diet. Mean age of the low carbohydrate group was 32 years and that of the low GI group was 35 years. Baseline mean body mass index of each group was 33.4 and 31.5 respectively. Initial mean fasting serum insulin levels were 113 in the low carbohydrate group and 79 in the low GI group. None had plasma glucose levels in the diabetic range. Baseline menstrual cycle lengths were 12 weeks in the low carbohydrate group and 14 weeks in the low GI group. They were reviewed at monthly intervals by the dietitian, who recorded anthropometric measurements and analysed food diaries. Biochemical and endocrine assays were taken at the first, third and last visits.
Results: Mean decrease in weight in the low carbohydrate group was 11 kg compared to 7 kg in the low GI group (P=0.007). The proportional improvements in body composition, insulin, lipid and testosterone levels were more marked in the low carbohydrate group but did not reach statistical significance. Plasma glucose levels remained stable throughout the study. Regular menstrual cycles were achieved in more women on the low carbohydrate diet.
Conclusions: Reduction in body weight led to an improvement in body composition and metabolic markers irrespective of the quality of the diet being followed. However, the low carbohydrate diet seemed to achieve a greater degree of improvement than the low GI diet.