Probiotic Intervention on Body Weight

Inclusion Criteria: * Aged 20 to 50 years. * Normal-weight participants: 18.5 kg/m² ≤ Body Mass Index (BMI) \< 24 kg/m². * Overweight or obese participants: BMI ≥ 28 kg/m², or 24 kg/m² ≤ BMI \< 28 kg/m² and a clinical diagnosis meeting semaglutide treatment indications (e.g., hyperglycemia, hypertension, dyslipidemia, fatty liver, obstructive sleep apnea, cardiovascular disease, etc.). * Willingness to participate in this study and provide signed informed consent. Exclusion Criteria: * Abnormal metabolic indicators (meeting any one of the following criteria is grounds for exclusion): 1\. Normal weight (18.5 kg/m² ≤ BMI \< 24 kg/m²): 1. Waist circumference ≥ 90 cm for men or ≥ 85 cm for women. 2. Fasting glucose ≥ 6.1 mmol/L or 2-hour postprandial glucose ≥ 7.8 mmol/L, or a confirmed diagnosis of diabetes. 3. Systolic blood pressure ≥ 130 mmHg or diastolic blood pressure ≥ 85 mmHg, or currently under antihypertensive treatment. 4. Fasting triglycerides (TG) ≥ 1.7 mmol/L; high-density lipoprotein cholesterol (HDL-C) \< 0.9 mmol/L in men or \< 1.0 mmol/L in women. 2\. Overweight or obese (BMI ≥ 24 kg/m²): 1. Fasting plasma glucose \> 11.1 mmol/L or HbA1c \> 9%, or previously diagnosed diabetes, or currently using insulin or any antidiabetic medication. 2. Blood pressure ≥ 160/100 mmHg, or clinically diagnosed stage 2 or stage 3 (moderate or severe) hypertension, or currently under antihypertensive treatment. 3. Use of lipid-lowering drugs (e.g., fibrates, bile acid sequestrants, statins, PCSK9 inhibitors) within the past 3 months, or TG ≥ 5.7 mmol/L, or LDL ≥ 4.9 mmol/L. * Pregnancy or lactation. * Self-reported weight change of more than 5 kg within the 90 days prior to screening. * Use of antibiotics, antimicrobials, or anti-inflammatory/analgesic salicylates (e.g., aspirin) within the 3 months prior to screening for 3 days or more. * Use of estrogen therapy or other hormonal medications within the past 6 months. * Use of GLP-1 receptor agonists or probiotics within the past 3 months. * Heavy alcohol consumption (females \> 40 g/day, approximately 250 mL of huangjiu \[yellow rice wine\], or 1000 mL of beer, or 100 mL of liquor per day; males \> 80 g/day). * Severe liver or kidney dysfunction (ALT, AST, or serum creatinine exceeding 3 times the upper limit of normal, UACR ≥ 30 mg/g, or eGFR \< 60 mL/min). * Gastrointestinal diseases affecting digestion and absorption (e.g., severe diarrhea, severe constipation, severe inflammatory bowel disease, peptic ulcer, gallstones, cholecystitis). * Underwent surgery within the past year (excluding appendectomy or hernia repair). * Severe cardiovascular or cerebrovascular diseases (e.g., heart failure, myocardial infarction, stroke, acute myocarditis, severe arrhythmia, or receiving interventional therapy). * Presence of metallic implants such as a cardiac stent or pacemaker. * Cancer or having received radiation or chemotherapy within the past 5 years. * Personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia, or a personal history of hyperthyroidism or hypothyroidism. * Chronic or acute pancreatitis. * Positive hepatitis B surface antigen (HBsAg), active tuberculosis, HIV, or other infectious diseases. * Currently participating in another clinical study or having done so within the past 3 months. * Claustrophobia. * Any psychiatric disorder such as attention-deficit/hyperactivity disorder (ADHD), bipolar disorder, or epilepsy (including current use of antiepileptic medications), or use of antidepressant medications. * Inability to read, write, operate a smartphone, or perform daily activities independently.