Inclusion Criteria:  Community dwelling 18 - 65 year old adults BMI 18.5 - 30 kg/m2 (n = 40, M:F = 1:1) BMI > 30 kg/m2 (n = 40, M:F = 1:1) OSAS patients with BMI > 30 kg/m2 using nasal continuous positive airway pressure (CPAP) treatment on an average > 4 h/d (n = 40, M:F = 1:1).  Exclusion Criteria:  Antimicrobial treatment within 3 months prior the baseline visit Inflammatory bowel diseases