Does a restricted energy low glycemic index diet have a different effect on overweight women with or without polycystic ovary syndrome?

Background Obese women with polycystic ovary syndrome (PCOS) may face additional barriers in achieving weight loss. We aimed to compare the effects of the hypocaloric low glycemic index (LGI) diet on anthropometric variables and insulin resistance in women with and without PCOS and investigate the effect of this diet on the clinical and hormonal features of PCOS women. Methods This interventional study was carried out at the Reproductive Endocrinology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Of 108 women invited for the purpose of the present study, 62 participants (PCOS = 28, non-PCOS = 34) followed a 24-week energy restricted LGI diet. Anthropometric, biochemical, hormonal and clinical measurements were documented at baseline, 12 weeks and 24 weeks with intervention. Results The percentages of weight loss achieved by both the PCOS and non-PCOS groups did not differ significantly (PCOS: -8.04% vs. non-PCOS: -8.09%). No significant difference in decrease of homeostatic model assessment of insulin resistance (HOMA-IR) was observed between the two groups (PCOS = − 0.83 ± 0.33, non PCOS = − 0.79 ± 0.28, P = 0.83). In PCOS women, significant reduction in total testosterone (− 0.91 ± 0.33 nmol/L, P = 0.006), FAI (− 4.47 ± 1.1, P