Background: Obstructive sleep apnea (OSA) is a very common disease in the general population that can cause deterioration in the quality of life, chronic diseases, road traffic accidents and excessive mortality in itself. The condition is characterized by repeated episodes of upper airway obstruction, accompanied by nocturnal oxygen desaturation, fragmented sleep and excessive daytime sleepiness. Objective: To evaluate body mass index (BMI) correlated to apnea-hypopnea index (AHI) and minimum O2 saturation (Nadir SaO2). Patients and Methods: A retrospective database analysis of medical records of One hundred fifty patients with OSA that performed at Almoosa Hospital, Saudi Arabia during the period from August 2016 to August 2019.BMI was calculated for each patient, as well as AHI and Nadir SaO2 recorded during polysomnography. AHI was used to evaluate the severity of OSA and to assess if there is correlation to BMI values. Results: The severity of OSA had significant positive correlation with BMI (ρ =0.13, P=0.005) and significant negative correlation with Nadir SaO2 (ρ = -0.27, P=0.001). BMI had significant negative correlation with Nadir SaO2 (ρ = -0.18, P=0.027). Conclusion: Higher BMI values were correlated with lower Nadir SaO2 during overnight polysomnography. Since hypoxia stress is a risk factor for cardiovascular diseases and alters the lipid metabolism, dietary consulting should be recommended in association with other treatment modalities for OSA.