Objective The ketogenic diet (KD) is a dietary intervention with potential therapeutic effects on polycystic ovary syndrome (PCOS), yet the existing evidence remains controversial. Furthermore, there is a lack of evidence-based medicine data for a comprehensive assessment of the safety of KD in the treatment of PCOS. This study aims to systematically evaluate, through a meta-analysis, the effects of KD on body composition, metabolic indicators, and reproductive hormone levels in overweight/obese patients with PCOS, and to explore its safety and clinical applicability.

Methods This study systematically searched PubMed, Web of Science, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang Database, and VIP Database. Randomized controlled trials (RCT) on KD for the treatment of PCOS were included, with the search time frame spanning from the establishment of each database to May 31, 2025. Two researchers independently screened and extracted data according to inclusion and exclusion criteria, and assessed the quality of the included literature using the Cochrane Handbook. The Q-test and inconsistency index (I²) were used to evaluate the heterogeneity of the results. Based on the level of heterogeneity, a fixed-effects model or a random-effects model was selected for data pooling. Sensitivity analysis was employed to explore the robustness of the results.

Results A total of 7 RCT studies involving 495 overweight/obese subjects were included in this study. Body composition analysis revealed that, compared with the control group, KD significantly reduced body mass index, body weight, waist circumference, waist-to-hip ratio, total fat mass, and visceral fat area in overweight/obese patients with PCOS (P < 0.05), but had no significant effect on fat-free mass. Analysis of glucose and lipid metabolism indicated that KD significantly decreased fasting blood glucose, fasting insulin, insulin resistance index, and triglycerides (P < 0.05), but had no significant impacts on total cholesterol, low-density lipoprotein cholesterol, or high-density lipoprotein cholesterol. Reproductive hormone analysis showed that KD significantly reduced luteinizing hormone, the ratio of luteinizing hormone to follicle-stimulating hormone, and total testosterone levels, while significantly increased sex hormone-binding globulin levels (P < 0.05), but had no significant effect on follicle-stimulating hormone. Sensitivity analysis suggested that the results were relatively robust. In terms of safety, no serious adverse reactions were observed during the KD intervention; however, further verification through high-quality RCTs with larger sample sizes and long-term interventions is still required.

Conclusion KD can effectively improve body composition, glucose metabolism, lipid metabolism indicators, and reproductive hormone levels in overweight/obese patients with PCOS. This study confirms that KD significantly increase sex hormone-binding globulin level and reduce visceral fat area. It is found that KD has a more pronounced effect on improving triglycerides compared to its effects on low-density lipoprotein cholesterol and high-density lipoprotein cholesterol. The current evidence does not indicate significant safety risks associated with KD, but relevant conclusions still require further confirmation with more high-quality evidence.