A recent study published in the British Journal of Nutrition reviewed clinical trials on the effects of a very low-carbohydrate ketogenic diet (VLCKD) in women with Polycystic Ovary Syndrome (PCOS). Researchers looked at body measurements, hormone levels, and metabolic health.
PCOS Challenges and Diet Solutions
PCOS affects about one in ten women of reproductive age. The condition is linked to insulin resistance, weight gain, and low-grade inflammation. These factors can cause irregular menstrual cycles, fertility concerns, and long-term health risks. Even small weight loss can improve cycles and increase chances of pregnancy.
Many diets are hard to maintain, but VLCKD may help. This diet reduces carbohydrates enough to trigger nutritional ketosis. It may lower insulin, reduce belly fat, and rebalance androgen hormones. However, most trials are short and strict, so long-term safety and effectiveness compared to other diets remain uncertain.
Study Approach
Researchers followed PRISMA guidelines and searched multiple medical databases for randomized controlled trials (RCTs) up to July 2025. Eligible participants were adult women with PCOS who followed a VLCKD.
Key Outcomes Measured
The study analyzed:
Body measurements: weight, BMI, waist size, body fat, and waist-to-hip ratio.
Hormones: testosterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH), sex hormone-binding globulin (SHBG), and LH/FSH ratio.
Metabolic markers: fasting glucose and insulin, insulin resistance (HOMA-IR), triglycerides, and cholesterol levels.
Results Across Countries and Diet Protocols
Twelve trials, involving over 800 women from Italy, China, Pakistan, and the U.S., were included. Diets lasted 4 to 24 weeks and restricted carbohydrates enough to induce ketosis while maintaining adequate protein. Protocols varied in calories and macronutrient composition.
Improvements in Body Weight and Fat
Women following VLCKD lost weight and body fat significantly. Average reductions included:
- Weight: −9.57 kg
- Waist circumference: −7.75 cm
- Body fat mass: −7.44 kg
- BMI: −3.45 kg/m²
- Waist-to-hip ratio: −0.02
These changes may lead to easier movement, better sleep, and improved comfort in daily life.
Hormonal Benefits
VLCKD also improved hormone levels related to PCOS:
- Free testosterone: −0.31 ng/dL
- Total testosterone: −7.21 ng/dL
- SHBG: +15.22 nmol/L
- LH: −3.97 U/L
- LH/FSH ratio: −1.04
FSH remained stable. These shifts suggest reduced hyperandrogenism and improved ovulation potential.
Better Blood Sugar and Insulin Control
Metabolic improvements included:
- Fasting glucose: −9.65 mg/dL
- Fasting insulin: −2.41 µU/mL
- HOMA-IR: −2.46
- Triglycerides: −29.95 mg/dL
Other cholesterol measures did not change significantly. These improvements could reduce “sugar crashes” and lower long-term risk of type 2 diabetes.
Limitations and Safety Considerations
Some trials had potential bias or missing data. Evidence certainty was generally moderate due to differences in diet protocols and adherence. Reported side effects in ketogenic diets, such as digestive discomfort or nutrient gaps, highlight the need for professional supervision. Trials also did not analyze results by PCOS phenotype, which could affect outcomes.
Conclusion
VLCKD appears to improve body weight, fat, hormones, and metabolic health in women with PCOS. It may help regulate cycles, increase comfort, and support fertility when supervised by healthcare professionals.
Future research should compare VLCKD with other diets over longer periods, track different PCOS phenotypes, and improve safety monitoring. Behavioral support and standardized diet protocols could also help women maintain these benefits in the long term.
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