Objective Obstructive Sleep Apnea Syndrome (OSAS) is a common sleep-related breathing disorder. Associations among Apnea-Hypopnea Index (AHI), Resting Metabolic Rate (RMR), body habitus differences, and otorhinolaryngologic abnormality may clarify the characteristics of patients with OSAS. In order to test this hypothesis, we aimed to compare the RMR, Modified Mallampati Scores (MMS), anthropometric measurements and body composition of male OSAS patients with simple snorers and to investigate the association among these parameters. Methods MMS were calculated, overnight polysomnography was performed, body mass index, neck, shoulder, chest, waist, hip and abdomen circumferences, body fat amount and ratio, lean body weight, body water amount and RMR were measured for all of the patients. Patients Ninety-eight male patients with suspected OSAS were included in the study. Results Fifty-one patients were diagnosed as OSAS and 47 patients were diagnosed as simple snorers. RMR, total body water, neck, shoulder and chest circumferences were significantly higher in OSAS patients than the simple snorers. The majority of the simple snorers was seen to have a MMS of stage 2 whereas OSAS patients had MMS of stages 3 and 4. AHI was significantly correlated with neck, shoulder, chest circumferences, total body water amount, MMS and RMR. Chest girth was found as the most important single predictor of sleep apnea in multivariate analysis. Conclusion We suggest that the increased RMR and chest circumference might have occured due to the condition resulting from the elevated AHI in patients with OSAS. Mallampati score should be routinely evaluated in OSAS patients.