The effects of a low-carbohydrate, ketogenic diet on the polycystic ovary syndrome Original paper

What was studied?

This pilot study examined the effects of a low-carbohydrate, ketogenic diet (LCKD) on metabolic and endocrine parameters in overweight and obese women with polycystic ovary syndrome (PCOS). Given PCOS’s well-documented link with insulin resistance and hyperandrogenism, the study hypothesized that carbohydrate restriction would improve insulin sensitivity and hormonal imbalance. The intervention involved instructing participants to consume fewer than 20 grams of carbohydrates per day over 24 weeks. Researchers assessed changes in body weight, fasting insulin, free testosterone, LH/FSH ratio, and subjective PCOS symptoms.

Who was studied?

Eleven women aged 18 to 45 with clinically diagnosed PCOS and a BMI ≥27 kg/m² were enrolled from the Raleigh-Durham area in North Carolina. The final analysis included five participants who completed the 24-week study. All participants were instructed to follow a strict LCKD and attended biweekly follow-ups for adherence monitoring and biochemical assessments. The group was predominantly Caucasian, and participants reported histories of chronic anovulation or hyperandrogenemia.

What were the most important findings?

Among the five women who completed the study, the LCKD led to a significant mean weight reduction of 12%, with individual weight loss ranging from 4% to 16.4%. More notably, there were substantial metabolic and hormonal improvements: fasting serum insulin dropped by approximately 54%, the LH/FSH ratio fell by 36%, and percent free testosterone decreased by 30%. These findings strongly suggest enhanced insulin sensitivity and reduced ovarian androgen production. Two of the women, previously experiencing infertility, became pregnant during the study period.

From a microbiome perspective, this is noteworthy because a ketogenic diet is known to modulate gut microbial composition. Prior studies associate ketogenic diets with increased abundance of Akkermansia muciniphila and Bacteroides species, both of which are linked to improved metabolic profiles, including insulin sensitivity and gut barrier integrity. Although microbiota were not directly assessed in this study, the improvement in metabolic parameters is consistent with microbial shifts observed in similar dietary interventions. The reduction in insulin likely suppressed hyperinsulinemia-induced androgen synthesis and improved sex hormone-binding globulin (SHBG) levels, thereby reducing circulating free testosterone. This is particularly relevant for clinicians considering microbiome-modulating dietary strategies as adjunctive treatment in PCOS.

What are the greatest implications of this study?

The study underscores that a ketogenic diet may serve as an effective non-pharmacological approach to reduce insulin resistance and hyperandrogenism in women with PCOS. This could potentially translate into improved ovulatory function and fertility. The LCKD demonstrated significant endocrine normalization within six months, which is meaningful considering the limited curative options currently available for PCOS. Clinicians should consider LCKD as a viable dietary strategy, especially for PCOS patients struggling with infertility, elevated androgens, or metabolic dysfunctions. Moreover, the potential microbiome-mediated mechanisms add further value by pointing to gut health as an emerging therapeutic axis in PCOS management. While the small sample size and lack of a control group limit generalizability, the results justify larger trials examining diet–microbiome–hormone interactions in this population.