question: BACKGROUND AND AIMS: COVID-19 is an emerging pandemic due to droplet infection of 2019-novel coronavirus (2019-nCoV). Due to its rapid transmission and high case-fatality rate, recognition of its risk and prognostic factor is important. Obesity has been associated with impaired immune system, increasing the susceptibility for 2019-nCoV infection. We aimed to study the impact of obesity to the prognosis and disease severity of COVID-19. METHODS: A systematic search and handsearching was conducted in four databases: Cochrane, MEDLINE, EMBASE, and PubMed. The identified articles were screened using the chosen eligibility criteria. We obtained three retrospective cohort studies (Wu J et al., Lighter J et al., and Simonnet A et al.) to be critically appraised using Newcastle Ottawa Scale. RESULTS: The findings of all included studies were consistent in stating the contribution of obesity as a risk factor to increase the requirement for advanced medical care. Study with the highest quality, Simonnet A et al., reported an increase need of invasive mechanical ventilation in COVID-19 patients with body mass index higher than 35 kg/m(2), OR: 7.36 (1.63–33.14; p = 0.021). This is associated with a higher mortality rate in obese population infected with COVID-19. CONCLUSION: Obesity is an independent risk and prognostic factor for the disease severity and the requirement of advanced medical care in COVID-19. This systematic review highlights a particularly vulnerable group – obese, and emphasises on the importance of treatment aggression and disease prevention in this population group.