Background: Some researchers administer a diet with a higher ratio of protein to carbohydrates (HP) in patients with polycystic ovary syndrome (PCOS), but there is a limited number of dietary interventions compared the effects of an HP diet with a standard protein (SP) diet. Therefore, the aim of this review was to compare the effects of energy-restricted HP diets with those of iso-calorically prescribed SP diets on anthropometric, metabolic, hormonal, and reproductive outcomes in women with PCOS.
 Materials and methods: Searches for English-language studies published between 2000 and 2014 were conducted using PubMed, Science Direct, and Scopus databases to identify all randomized controlled trials that compared HP diet with SP diet.
 Results: There was no difference in anthropometric outcomes between two different diets. There was no difference in reproductive outcomes between the two dietary treatments. Weight loss decreased testosterone, free testosterone, or FAI (Free Androgen Index) and increased SHBG, independent of prescribed diet. There was no difference in metabolic outcomes between the two dietary treatments. A standard-protein weight-loss diet reduced HDL- cholesterol, while no changes occurred for a high protein weight-loss diet. The high-protein diet reduced total cholesterol to HDL-C ratio. Weight loss, independent of diet composition, decreased fasting insulin, insulin resistance and Improvements in lipid profiles.
 Conclusion: High protein diet caused subtle and inconsistent changes in metabolic variables, and weight loss results in clinical benefit, regardless of diet composition, in women with PCOS.
Keywords: High protein diet, Standard diet, PCOS, Fertility, Metabolic, Anthropometric outcomes.