Inclusion Criteria:  Local residents aged between 30-60 years old; Stable weight (<5% weight change over last 3 months); Central obesity defined as waist circumference ≥90 cm in males or ≥80 cm in females, Plus any two of the following four conditions i) Elevated triglycerides: serum triglycerides ≥150 mg/dL (1.7 mmol/L); ii) Reduced HDL cholesterol: serum HDL-c <40 mg/dL (1.03 mmol/L) in males or <50 mg/dL (1.29 mmol/L) in females; iii) Elevated blood pressure: systolic blood pressure ≥130 mmHg or diastolic blood pressure ≥85 mmHg; iv) Elevated fasting plasma glucose: fasting plasma glucose ≥100 mg/dL (5.6 mmol/L) Absence of any systemic, cardiovascular diseases, as well as infections within the previous month; Absence of any diet or medication that might interfere with metabolic homoeostasis and gut microbiota, especially antibiotics and probiotics 4 weeks before recruitment.  Exclusion Criteria:  Acute illness or current evidence of acute or chronic inflammatory of infective diseases; Participation in regular diet program more than 2 times per week in the latest 3 months prior to recruitment; Mental illness rendering them unable to understand the nature, scope, and possible consequences of the study.