A Ketogenic Diet Followed by Gradual Carbohydrate Reintroduction Restores Menstrual Cycles in Women with Polycystic Ovary Syndrome with Oligomenorrhea Independent of Body Weight Loss: Results from a Single-Center, One-Arm, Pilot Study

Background/Objectives: Polycystic ovary syndrome (PCOS) is a common endocrine disorder in women of fertile age. Some studies suggest that a ketogenic diet (KD) may have a role in treating PCOS. We aimed to demonstrate the long-term effectiveness of a KD in PCOS. Methods: Eighteen patients with PCOS phenotype A were enrolled: 28% were of normal weight, 28% were overweight, and 44% had obesity. All participants followed a KD without meal replacements for 45 days. After this period, patients underwent gradual carbohydrate reintroduction over 45 days, and thereafter healthy eating indications were given. Twelve patients completed the study. The patients were assessed at baseline and after 6 months. Anthropometric data, body composition, pelvic ultrasound, blood chemistry, hirsutism, and menstrual cycles frequency were recorded; Results: Besides improvement in anthropometric parameters, menstrual cycles (p 0.012), ovarian volume (p 0.029), FSH (p 0.05), LH (p 0.037), and progesterone (p 0.017) improved independently of weight or fat loss. However, testosterone and hirsutism improvements were influenced by weight and fat mass reduction. Conclusions: Our study showed that a KD followed by gradual carbohydrate reintroduction in PCOS has beneficial effects medium term, mostly independent of body weight loss, even in normal-weight women, suggesting that nutritional ketosis exerts beneficial effects per se.