Food Intake-Related Brain and Metabolic Responses in Obesity

Inclusion Criteria: Obese participants: 1. BMI ≥ 28 kg/m²; 2. Age 18-40 years; 3. Any gender; 4. Right-handed. Healthy control participants: 1. BMI 18.5-23.9 kg/m²; 2. Age 18-40 years; 3. Any gender; 4. Right-handed. Exclusion Criteria: 1. Diabetes mellitus; 2. Contraindications or allergies to any ingredient in the standardized meal or macronutrient challenges used in this study; 3. Central nervous system disorders (e.g., traumatic brain injury, acute cerebral infarction, epilepsy) or psychiatric disorders (e.g., depression, schizophrenia); use of medications acting on the central nervous system within the past 3 months or long-term use; 4. Severe impairment of liver, kidney, heart, or gastrointestinal function, including alanine aminotransferase (ALT) and/or aspartate aminotransferase (AST) levels \>2 times the upper limit of normal; estimated glomerular filtration rate (eGFR) \<45 mL/min/1.73 m² calculated by the CKD-EPI equation; history of unstable angina or myocardial infarction within the past 3 months, or heart failure classified as New York Heart Association (NYHA) class II or higher; history of gastrointestinal stoma, bowel resection, intestinal obstruction, or peptic ulcer disease; 5. Contraindications to MRI, such as implanted metallic devices or claustrophobia; 6. Pregnancy or lactation; 7. Participation in another clinical trial currently or within the past 3 months; use of nutritional supplements within the past 3 months or long-term use; 8. History of prior metabolic/bariatric surgery; 9. Use of antibiotics or probiotics within the past 1 month; 10. Use of medications affecting metabolism or causing weight loss within the past 1 month; body weight fluctuation exceeding 3 kg during the month prior to screening; 11. Unusual dietary habits; daily alcohol intake \>40 grams, smoking \>10 cigarettes per day, or coffee consumption ≥2 cups per day.