Effects of ketogenic diets on polycystic ovary syndrome: a systematic review and meta-analysis

This systematic review and meta-analysis aimed to evaluate the effects of ketogenic diet (KD) and very-low-energy ketogenic therapy (VLEKT) protocols on various health outcomes in patients with polycystic ovary syndrome (PCOS) and increased body weight.

A systematic search was conducted across Scopus, PubMed, Cochrane, and Embase databases from their inception through January 2025, using a predefined search strategy. Studies were selected based on the PICOS criteria. Data extraction focused on anthropometric measures, glycometabolic and lipid profiles, and hormone levels. Controlled studies were analyzed to evaluate the effects of high-fat KDs and VLEKT compared to low calorie diets (LCDs). Additionally, uncontrolled studies were included, and the outcomes following high-fat KDs or VLEKT were compared to baseline values (before-after study design). A sub-analysis was also performed to compare VLEKT with high-fat KDs. We assessed the quality of the evidence, as well as heterogenity, sensitivity, and publication bias.

A total of 10 studies were included in the analyses, comprising three randomized controlle studies (RCTs), one non-randomized intervention study, four cohort studies, and two case series. Two RCTs comparing VLEKT and high-fat KDs with LCDs found no significant effect on body weight. However, both high-fat KDs and VLEKT were associated with reductions in body mass index (BMI) and fat mass percentage in patients with PCOS. Significant improvements in weight, BMI, fat mass, and lean mass were observed following high-fat KDs or VLEKT interventions compared to baseline values, with no substantial differences between the two diet types. Regarding glycometabolic outcomes, both high-fat KDs and VLEKT reduced serum glucose levels and the homeostatic model assessment index compared to LCDs, with VLEKT showing slightly more favorable effects. In terms of the lipid profile, both high-fat KDs and VLEKT lowered total cholesterol and triglyceride levels, and VLEKT showing greater efficacy in triglyceride reduction. Hormonal analyses from two RCTs showed that both high-fat KDs and VLEKT were associated with lower serum luteinizig hormone (LH) levels compared to LCDs. Additionally, both high-fat KDs and VLEKT led to reductions in LH and total testosterone levels relative to baseline, with VLEKT showing a slight advantage in lowering LH and follicle-stimulating hormone levels.

High-fat KDs and VLEKT show beneficial effects on weight, body composition, glycometabolic parameters, and hormone profile in women with PCOS. VLEKT may provide additional advantages, particularly in reducing fat mass and lowering triglyceride levels. Further studies with larger sample sizes and more robust study designs are needed to confirm these findings.