Objectives: To investigate the effect of BMI on the outcome of COVID-19 patients.

Patients &Methods: 200 patients with  confirmed Covid-19 ,were included and divided into 4 groups according to their BMI: Underweight group (n= 16):  with BMI below 18.5 kg/m2. Normal group (n= 62): with BMI ranging between 18.5 and 24.9 kg/m2. Overweight group (n= 66): with BMI ranging between 25 and 29.9 kg/m2. Obese group (n= 56):  with BMI above 30 kg/m2. Detailed history, clinical examination and outcomes were recorded for all patients.

Results: Admission to ICU was significantly higher among underweight patients (75%) and obese patients (78.6%) (P< 0.001). The majority of underweight patients (62.5%) and obese patients (57.1%) had critical disease while majority of normal weight patients (48.4%) and overweight patients (57.6%) patients had severe disease. Invasive MV was frequently used in underweight patients (50%) and obese patients (42.9%). Majority of underweight (75%) and obese patients (50%) were deteriorated and died while majority of normal weight patients (90.3%) and overweight patients (75.8%) were improved and discharged (P< 0.001). ARDS, cardiac complications, neurological complications, hematological  complications, incidence of myalgia and incidence of bed sores were most frequent among obese patients and overweight patients. Occurrence of acute kidney injury was significantly higher among underweight patients (37.5%), and obese patients (28.6%) when compared with other classes (P=0.004)

Conclusion: body mass index is a major contributing factor for the outcome in patients with COVID-19 infection and patients with the extremes of body mass index was associated with the worst prognosis.