Keto Slashes Testosterone Levels in PCOS Women With Obesity, and Weight Loss May Not Be Why

Polycystic ovary syndrome affects roughly 10 to 13 percent of women of reproductive age, and elevated androgens sit at the center of its most disruptive symptoms: irregular cycles, excess hair growth, and impaired fertility. Diet is considered a first-line intervention, particularly for women who are overweight or obese, but which dietary pattern works best for hormone control has remained genuinely contested. A new meta-analysis published in the Journal of Endocrinological Investigation by Elisa Maseroli and colleagues now offers the most comprehensive evidence to date that a ketogenic diet can meaningfully reduce total testosterone in this population, and that the benefit may not depend on weight loss at all.

Ketogenic Diet Reduces Total Testosterone in Overweight PCOS Patients

The headline number from the pooled analysis: women following a ketogenic diet showed a statistically significant reduction in total testosterone (TT) of 0.35 nmol/L on average (95% CI: 0.24 to 0.46). Sex hormone-binding globulin (SHBG), a protein that binds testosterone and makes it biologically inactive, rose by a mean of 19.50 nmol/L (95% CI: 6.90 to 32.11). Both effects held across different study designs. The reduction in free testosterone trended in the right direction but did not reach statistical significance, a distinction worth keeping in mind given that free testosterone is the biologically active fraction.

These findings align with earlier work suggesting ketogenic diets improve reproductive hormone profiles in PCOS, including reductions in LH/FSH ratio and increases in SHBG. The Maseroli meta-analysis extends that picture with a broader dataset and a more rigorous look at what might be driving the effect. LH levels dropped significantly as well (mean difference: 3.48 IU/L; 95% CI: 2.26 to 4.71), as did the LH/FSH ratio (mean difference: 0.99; 95% CI: 0.54 to 1.44), suggesting the hypothalamic-pituitary axis is responding alongside the ovaries.

Why Lowering Androgens Matters Beyond Symptom Relief

Biochemical hyperandrogenism in PCOS is not just a hormonal inconvenience. Research has linked elevated androgens in PCOS to higher rates of gestational diabetes and preeclampsia, meaning the reproductive stakes extend well into pregnancy. Women who cannot normalize their androgen levels face compounding risks across the reproductive lifespan.

The ketogenic diet's effect on SHBG also carries implications beyond PCOS. Rising SHBG levels are associated with improved liver function, and the authors note that increased SHBG may benefit women with metabolic dysfunction-associated steatotic liver disease, a condition that frequently co-occurs with PCOS and obesity. Weight loss and improved insulin sensitivity from the diet reinforce this benefit through a separate pathway. In the meta-analysis, the ketogenic diet also produced significant reductions in BMI, waist circumference, fasting glucose, fasting insulin, HOMA-IR, total cholesterol, and triglycerides, a broad metabolic improvement rarely seen from a single dietary intervention.

How the Meta-Analysis Was Built and What It Covered

Maseroli's team searched five databases, including MEDLINE, Embase, and the Cochrane CENTRAL register, covering studies published up to March 1, 2025. They included women aged 18 and older, in the reproductive age range, with a BMI of at least 25 kg/m2, and a confirmed PCOS diagnosis by Rotterdam or ESHRE/ASRM criteria. Ketogenic diet protocols varied but all capped carbohydrate intake at 50 grams per day or below. Some studies used very low-calorie ketogenic diets (VLCKD) at under 800 kcal per day with fewer than 30 grams of carbohydrates; others used less restrictive low-carbohydrate ketogenic versions.

Because study protocols and populations differed considerably, the team used a random-effects model throughout. As pooling results across studies can sharpen statistical estimates that individual small trials cannot produce on their own, this approach was appropriate given the heterogeneity present. Sensitivity analyses stratified by study design (randomized controlled trials versus pre-post observational studies) confirmed that the SHBG increase was robust regardless of design, while the total testosterone reduction was strongest in the RCT subset.

The Weight-Independent Signal Points Toward Ovarian Ketosis

Perhaps the most scientifically striking result is the independence of the testosterone reduction from weight loss itself. Neither changes in BMI nor changes in fasting insulin nor shifts in the LH/FSH ratio significantly modified the reduction in TT across studies. That pattern suggests the ketogenic diet may be doing something to ovarian steroidogenesis directly, not merely as a downstream consequence of losing fat.

Experimental evidence supports this idea. Ketone supplementation with beta-hydroxybutyrate has been shown to acutely lower circulating androgens and glucose in women with PCOS. Animal studies suggest ketogenic diets reduce granulosa cell apoptosis by inhibiting the cGAS-STING inflammatory pathway, and beta-hydroxybutyrate suppresses NLRP3 inflammasome activation, a known driver of ovarian inflammation. Butyric acid, a short-chain fatty acid produced during ketogenic metabolism, has been shown to improve ovarian function and reduce local inflammatory markers in obese PCOS mouse models. Taken together, the data support a direct anti-inflammatory and potentially anti-androgenic effect of nutritional ketosis on the ovary, independent of caloric restriction.

Real Limitations and Unanswered Questions

This evidence is emerging, not settled. The included studies were mostly small, short in duration, and many were rated as low quality. Testosterone measurements used different assay methods across studies, including LC/MS and various immunologic approaches, introducing measurement heterogeneity that a random-effects model can only partially address. Free testosterone, arguably the more clinically relevant metric, did not show a statistically significant change in the pooled analysis.

The role of physical activity, itself a first-line PCOS therapy, was not evaluated alongside dietary changes in most included studies, leaving open the question of whether exercise modifies the ketogenic diet's hormonal effects. Reproductive outcomes such as cycle regularity and fertility showed qualitative improvements across studies, but heterogeneity in reporting made a formal meta-analysis of those outcomes impossible. Animal research also raises questions about potential long-term metabolic consequences of sustained ketogenic diets, including effects on liver function and blood sugar regulation, though those data are in mice and do not translate directly to the structured short-term protocols used in PCOS trials.

For now, the ketogenic diet looks like a genuinely promising short-term hormonal intervention for overweight and obese women with PCOS, one that may work through pathways distinct from simple weight loss. Larger, longer, and better-standardized trials are the obvious next step before it can be placed more firmly in clinical guidelines.

Evidence rating

EMERGING — 80/100

Caveats:

• The pooled sample sizes are small (n=290 for the primary testosterone outcome) and the authors themselves rate the underlying studies as mostly low quality.
• Significant heterogeneity across studies limits confidence in the pooled estimates.
• A direct causal link between ketosis and improved ovarian function cannot be established from the available data.
• Funding source was not disclosed by the authors.

Systematic review and meta-analysis pooling RCTs and pre-post studies (primary outcome n=290). Reports statistically significant reductions in total testosterone and increases in SHBG, with RCT-specific analysis confirming a moderate benefit versus control. Results show association with mechanistic speculation; a definitive causal pathway has not been established. Underlying studies are rated mostly low quality with substantial heterogeneity, and independent large-scale replication has not yet been conducted.

References

1. Elisa Maseroli, Chiara Alfaroli, Michela Cirillo, et al. (2026). Ketogenic diet as a therapeutic intervention for biochemical hyperandrogenism in PCOS women with obesity or overweight: a meta-analytic study. Journal of Endocrinological Investigation. https://doi.org/10.1007/s40618-026-02924-1
2. Karniza Khalid, Saraswathy Apparow, Irma Liyana Mushaddik, Amalina Anuar, Syed A A Rizvi, Anasufiza Habib (2023). Effects of Ketogenic Diet on Reproductive Hormones in Women With Polycystic Ovary Syndrome. Journal of the Endocrine Society. https://doi.org/10.1210/jendso/bvad112
3. Xiaohan Guo, Yingsha Yao, Ting Wang, Juanhong Wu, Ruoan Jiang (2024). The impact of hyperandrogenemia on pregnancy complications and outcomes in patients with PCOS: a systematic review and meta-analysis. Hypertension in Pregnancy. https://doi.org/10.1080/10641955.2024.2379389
4. Alain J. Nordmann, Benjamin Kasenda, Matthias Briel (2012). Meta-analyses: what they can and cannot do. Swiss Medical Weekly. https://doi.org/10.4414/smw.2012.13518
5. New Study in Mice Reveals Long-Term Metabolic Risks of Ketogenic Diet – University of Utah Health. healthcare.utah.edu. https://healthcare.utah.edu/news/2025/10/ketogenic-diet-risks