Study aim: Determining the effect of a fasting-mimicking diet and synbiotic supplementation on SIRT1 gene expression, serum IGF-1 levels, insulin resistance index, and metabolic parameters in obese adults with metabolic syndrome Design: A three-arm, parallel-group, randomized, controlled clinical trial involving 186 participants. Randomization will be performed using a stratified approach with variable-sized blocks, based on gender and body mass index (BMI) categories. Outcome assessors and the data analyst will be blinded to group allocation. Settings and conduct: This clinical trial will be conducted at the Imam Khomeini Hospital in Urmia. After screening and obtaining informed consent, participants will be randomly allocated to three groups and followed for 3 months. Outcome assessors and data analysts will be blinded to group allocation. Participants/Inclusion and exclusion criteria: Major inclusion criteria before randomization: Age 18 to 55 years, both sexes, BMI greater than 30 kg/m², central obesity, and metabolic syndrome according to the International Diabetes Federation criteria. Major non-inclusion criteria before randomization: Chronic liver, kidney, or cardiovascular diseases, malignancy, inflammatory diseases or severe gastrointestinal disorders, uncontrolled thyroid disorders, pregnancy or breastfeeding, smoking or alcohol consumption, recent use of antibiotics or probiotic and prebiotic supplements, use of medications affecting metabolism, significant weight change during the previous three months Intervention groups: Group 1: Continuation of the usual diet, general healthy eating recommendations, and daily use of one placebo capsule for 12 weeks.Group 2: Fasting mimicking diet for 3 months, consisting of one 5 day cycle each month with continuation of the usual diet on the remaining days.Group 3: Fasting mimicking diet similar to Group 2, along with daily use of one synbiotic capsule for 12 weeks. Main outcome variables: SIRT1 gene expression; serum IGF-1; HOMA-IR; serum insulin