This study aims to evaluate the effects of a 16:8 time-restricted feeding (TRF) model on anthropometric, metabolic, and hormonal parameters in women with polycystic ovary syndrome (PCOS). In addition, the study will assess participants' food preferences, nutrient intake, and gastrointestinal hormone responses, alongside serum glucose, insulin, and glucagon levels, during ad libitum breakfast meals served at the beginning and end of the intervention.
The study consists of three groups: women with PCOS following a 16:8 TRF model for 12 weeks, women with PCOS following an energy-restricted diet for 12 weeks, and healthy women following a 16:8 TRF model for 12 weeks. Women aged 18-40, with PCOS based on the Rotterdam criteria, will be included in the PCOS groups, while those without PCOS-related symptoms will form the control group. Exclusion criteria include pregnancy, lactation, use of hormonal medications, and the presence of comorbidities such as diabetes or severe liver/kidney dysfunction.
Participants in the TRF groups will consume their daily caloric intake within an 8-hour eating window, fasting for the remaining 16 hours, while the energy-restricted group will follow a balanced diet without timing restrictions. Adherence to the dietary interventions will be monitored through weekly 24-hour dietary records. At baseline, participants will complete a demographic questionnaire, receive nutritional education for their nutritional plan, and undergo assessments for anthropometric and blood pressure measurements, sleep quality, food cravings, and physical activity. Biochemical analyses will evaluate thyroid and sex hormones, electrolytes, liver enzymes, lipid profiles, and hemograms. Additionally, all participants will wear smart wristbands (FitBit Charge 5) throughout the study to track sleep and physical activity.
At the beginning and end of the study, participants will consume a standardized ad libitum breakfast meal during the early follicular phase (days 2-5 of menstrual bleeding). Participants will have 30 minutes to eat as much as they wish, and their consumption will be recorded by a dietitian. The nutrient content of the consumed foods will be analyzed using the Nutrition Information System (BEBIS) software. Blood samples will be collected and visual analogue scala (VAS) will be filled at fasting and at 30, 60, 90, and 120 minutes post-meal. Serum glucose, insulin, glucagon, ghrelin, and incretin hormones will be analyzed using the enzyme-linked immunosorbent analysis (ELISA) method.
Data analysis will be performed using SPSS 23.0 via appropriate statistically analysis. Statistical significance is set at p\<0.05.
For study groups of women diagnosed with polycystic ovary syndrome (PCOS)
Aged between 19 and 35 years, with a diagnosis of PCOS
No chronic diseases diagnosed by a physician, other than PCOS
Body mass index (BMI) between 25 and 40 kg/m²
Being in the menopause, pregnancy, or lactation period
Having a diagnosis of any chronic disease (e.g., hypertension, diabetes mellitus, cardiovascular disease, etc.) other than PCOS, as determined by a physician
Having hyperprolactinemia, congenital adrenal hyperplasia, androgen-secreting tumors, thyroid disorders, Cushing's syndrome, hepatic or renal dysfunction
Using antihyperlipidemic, antihypertensive, or glucocorticoid medications
Parallel
Dietary Intervention (time-restricted feeding model (16:8))
Other interventionTime-Restricted Feeding (16:8 model): Participants can consume food in any amount during an 8-hour window (08:00-16:00), but no food or energy-containing drinks are allowed during the remaining 16-hour fasting period.
Dietary Intervention (energy restricted dietary intervention)
Other interventionParticipants' daily energy needs are calculated based on their basal metabolic rate and physical activity. The energy intake is then reduced by 15-25%. The diet plan consists of 3 main meals and 2-3 snacks, with the daily intake of carbohydrates, proteins, and fats making up 50-60%, 15-20%, and 25-30% of the total daily energy, respectively.
Changes in body mass index (BMI)
BMI will be calculated using weight (kg) and height (m²). Weight and height will be measured separately and used to derive BMI as a single reported outcome.
Changes in serum fasting glucose and lipit profile
Changes in fasting glucose, triglycerides, total cholesterol, low density lipoprotein-cholesterol, and high density lipoprotein-cholesterol (HDL-C) levels will be measured via enzymatic biochemical analysis. All values will be reported in millimolar (mM) and analyzed collectively as metabolic biomarkers.
Changes in appetite-related hormones (insulin, glucagon, ghrelin, glucagon-like peptid-1, and gastric inhibitory peptide)
Changes in insulin, glucagon, ghrelin, glucagon-like peptide-1, and gastric inhibitory peptide levels will be measured via enzyme-linked immunosorbent assay (ELISA kits). All values will be reported in nanomolar (nM) and analyzed collectively as appetite-regulating hormones.
Food craving
Compare food craving scores (from the Food Craving Questionnaire) at baseline and across the intervention period.
Sleep quality
Compare sleep quality (from the Pittsburgh Sleep Quality Index) at baseline and across the intervention period.
Physical activity
Compare physical activity level (from the International Physical Activity Questionnaire - Short Form) at baseline and across the intervention period.
Change in daily energy intake
Compare changes in daily total energy intake (kcal) at the beginning and end of the intervention.
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