Polycystic ovary syndrome (PCOS) is the most common endocrinopathy in reproductive-aged women, affecting 6-21% (depending on the applied diagnostic criteria) of this population worldwide. PCOS is characterized by hyperandrogenism and/or chronic anovulation which can manifest with a range of symptoms (e.g., hirsutism, acne, oligomenorrhea, and infertility) and is associated with increased risk of cardiometabolic diseases, including hypertension, dyslipidemia, insulin resistance (IR), and type 2 diabetes mellitus (T2DM). Moreover, PCOS is linked to increased psychological morbidity (e.g., increased risk of stress, depression, low self-esteem, poor body image, and reduced health-related quality of life). The exact PCOS etiology is unknown, but increased adiposity is considered pivotal. Indeed, almost 90% of women with PCOS are overweight or obese, and even moderate weight loss (e.g., 5%) may result in clinically meaningful improvements in hyperandrogenism and menstrual regularity. Also, women with PCOS often have more severe IR than weight-matched women without PCOS, whilst their increased susceptibility to obesity may further exacerbate IR and the accompanying metabolic and reproductive dysfunctions. As such, women with PCOS exhibit an increased risk of impaired glucose tolerance and T2DM regardless of weight and age. Management of overweight/obese women with PCOS focuses on weight loss through regular exercise and diet, aiming to alleviate its clinical manifestations and lower the related risk of T2DM and cardiovascular disease. Fasting-induced negative energy also potently affects the hormones such as estradiol, testosterone, and leptin; and complex interactions exist between metabolic signals and ovarian steroids. However, fasting is difficult to implement. It is of great interest to develop feasible and efficacious fasting-mimicking diets (FMD) to alleviate the burden of fasting while preserving the beneficial effects of fasting. In a case study, a 23-year-old female diagnosed with PCOS had her persistent cystic acne resolved after just 3 cycles of self-administered fasting-mimicking dieting. In addition, FDM induces a reduction in insulin levels, fasting glucose, BMI, decreased adiposity, and inflammation rates. The investigators hypothesize that a specially designed FMD will induce physiological changes similar to prolonged fasting and will decrease risk factors associated with metabolic syndrome and alleviate symptoms of PCOS.

The purpose of the study is to evaluate the effect of FMD in women with PCOS. Regarding the study model, a crossover will be applied. Our crossover design is the simplest model known as 2 x 2 where two treatments are compared in two-period, two-sequence model. Each washout, between consecutive periods, is done so that the previous treatment does not affect the response to the next treatment. The main advantage of a crossover design over the parallel group is the opportunity it offers to compare the effects of treatments within-subjects, which is not possible with a conventional parallel-group design. Additionally, a crossover design usually requires a smaller sample size to reliably estimate the magnitude of the treatment effect. That is, any component of an individual's response that is consistent over time is removed from the treatment comparison. Study participants will be randomized and assigned to arm 1 (n° = 50, control patients) or arm 2 (n° = 50, patients undergoing FMD). Patients in the FMD group will be asked to consume FMD, which will be provided with a box, for 5 continuous days, and to return to their normal diet after completion until the next cycle which will start 25 days later, for a total of three months.

The two groups will then be exchanged in the third month so that the control group will also be subjected to FMD in the following three months.

The main parameters that will be texted, are all major symptoms associated with PCOS, including menstrual cycle regularity, ovarian morphology (by ultrasound); hirsutism (by the Ferriman-Gallwey (FG) scoring method), and acne score. Moreover, improvement in metabolic, inflammatory, and psychological markers will be also evaluated.

Both control and FMD patients will complete anthropometric measurements every month (at the end of each FMD cycle). After three months, patients will be crossed for another 3 months: patients with arm 1 control will be instructed to follow FMD, while patients with arm 2 undergoing FMD will be asked to continue their normal diet. Follow-up exams will be conducted for both groups at the end of the 6th month. Thereafter, all patients will be asked to continue their normal diet for another three months and will undergo further follow-up at the end of the ninth month. Blood chemistry analyzes will be performed at time zero, at 3 and 6 months, while gynecological and nutritional checks will be performed at time zero at 3 to 6 months and at the end of the study (t = 9 months). The total duration of the study is 9 months. The evaluation of the menstrual history and the anthropometric parameters will be measured during the gynecological and nutritional checks. The psychological/psychiatric evaluation will be carried out at T0, at 3 to 6 months, and at 9 months. Blood samples will also be used for IGF-1 analyzes (IFOM, Milan). Both control and FMD patients will fill out a food diary. Patients undergoing FMD will be contacted by phone for nutritional assistance once a day during the 5 days of FMD. Additionally, to assess adherence to the 5-day nutritional plan for FMD, patients will independently assess their ketonuria with appropriate sticks. Every month, all enrolled patients will note the possible date of menstruation and the duration of the cycle.