Mediterranean Diet Combined With a Low-Carbohydrate Dietary Pattern in the Treatment of Overweight Polycystic Ovary Syndrome Patients Original paper

What was studied?

This randomized controlled clinical trial evaluated the effects of a combined Mediterranean and low-carbohydrate (MD/LC) dietary pattern compared to a standard low-fat diet in overweight women diagnosed with polycystic ovary syndrome (PCOS). Conducted over 12 weeks, the study aimed to determine whether this novel dietary model could more effectively improve anthropometric, metabolic, and reproductive endocrine parameters. While the low-fat diet restricted fat intake to under 30% of daily calories, the MD/LC model restricted carbohydrate intake to under 100 g/day, increased fat and protein intake, and emphasized traditional Mediterranean components like whole grains, olive oil, vegetables, legumes, and seafood.

Who was studied?

Seventy-two overweight women (BMI ≥ 24 kg/m²), aged 16–45 years, with a PCOS diagnosis based on the Rotterdam criteria were recruited from Changhai Hospital in China. After exclusions and dropouts, 30 participants completed the Mediterranean and low-carbohydrate diet and 29 completed the LF diet. All participants were of Chinese descent, had no other endocrine, cardiovascular, or metabolic conditions, and were not taking medications affecting insulin or lipid metabolism. Dietary intake was closely monitored, and participants were supported with professional dietetic guidance via digital communication tools.

What were the most important findings?

The MD/LC diet group demonstrated significantly greater reductions in body weight, BMI, waist circumference, body fat percentage, and waist-to-hip ratio than the LF group. Notably, the MD/LC group also experienced more profound improvements in metabolic markers: fasting insulin, HOMA-IR, and triglyceride levels dropped more substantially, while insulin sensitivity measured by QUICKI improved to a greater extent. Reproductive hormone profiles also responded better to the MD/LC diet. Total testosterone, luteinizing hormone (LH), and LH/FSH ratio all decreased more prominently in the MD/LC group, suggesting improved ovulatory function and androgen regulation.

Though the study did not measure microbiome outcomes directly, the dietary model has strong implications for gut microbial modulation. The Mediterranean diet is known to promote increased abundance of beneficial microbes such as Faecalibacterium prausnitzii, Bifidobacterium spp., and Lactobacillus spp., while low-carbohydrate diets reduce the fermentable carbohydrate load, possibly altering SCFA-producing bacteria ratios. The observed improvements in insulin sensitivity, inflammation markers, and lipid metabolism align with known microbiome-mediated metabolic pathways, suggesting that the MD/LC diet could drive favorable microbial shifts that improve PCOS outcomes.

What are the implications of this study?

This study highlights the superior efficacy of a calorie-restricted Mediterranean/low-carbohydrate diet in improving the key clinical features of PCOS compared to a traditional low-fat diet. Clinically, this offers a refined, evidence-based dietary model that targets obesity, insulin resistance, and hyperandrogenism—three interlinked hallmarks of PCOS. Importantly, the diet’s structure promotes microbial diversity and metabolite production, suggesting a dual mechanism of action: direct endocrine and metabolic effects, and indirect microbiome-mediated modulation. For clinicians managing PCOS, especially in overweight patients, the MD/LC model provides a practical and sustainable intervention that integrates metabolic restoration with potential microbiome optimization. Future trials with microbiome sequencing are warranted to validate these microbial associations and inform personalized nutrition strategies in PCOS treatment.