This is a prospective observational study. A total of 112 women with PCOS and insulin resistance will be recruited and randomized into two groups according to their body mass index (BMI), i.e. normal weight (BMI=18.5-23Kg/m2) group and overweight or obese (BMI > 23Kg/m2) group1. The acupuncture treatment will last for six months, 3 times per week, 30 minutes per treatment. The primary outcome is changes in insulin sensitivity from baseline to after 6 months of acupuncture treatment measured by OGTT.