The aim of this study was to assess the impact of obesity on outcomes in patients with severe COVID-19. This was a prospective observational study of 109 patients with severe COVID-19 treated in either intensive care (ICU) or high dependency care units (HDU) at the National Hospital Kandy, Sri Lanka. The mean BMI of the cohort was 21.5 kg/m2 (SD 3.53), with the commonest and least common BMI categories being normal BMI (42.2%) and obesity (13.8%) respectively. There was no significant difference in survival rates among the BMI categories (p = 0.301), but 60% people living with obesity survived compared to 32.6% with normal BMI. A lower proportion of people living with obesity compared to those without obesity required ICU care (60% vs. 84%; p=0.028) and intubation and ventilation (13.3% vs. 46.8%; p = 0.015) respectively. People living with obesity required non-invasive-ventilation (NIV) for a longer duration (median 6 days) compared to those with normal BMI (median 3 days), underweight (median 3 days) and overweight (median 2 days) (p = 0.017). People living with obesity had non-significantly higher arterial PaCO2 (median 61 mmHg), followed by people with overweight (median 41 mmHg), normal BMI (median 38), and underweight (median 37 mmHg) (p = 0.076), but had no significant difference in SpO2 (p = 0.273) or PaO2 (p = 0.371) among the BMI categories. The longest duration of insulin infusion was required in people living with obesity (median 181 hours), followed by normal BMI (median 102 hours), underweight (median 35 hours), and overweight (34 hours) (p = 0.01). There was no significant difference in daily insulin dose requirement based on BMI category (p = 0.212). People living with obesity experienced lower rates of ICU admission and intubation, but had more carbon-dioxide retention and required longer durations of NIV and insulin infusion in severe COVID-19.