AIM: The COVID-19 pandemic is a global health emergency, and therefore the prevention and treatment of this disease is an important priority of world health. In the present study, some risk factors, including unhealthy nutrition, obesity, and physical inactivity, were assessed in patients infected with SARS-CoV-2, and their effects on the severity and duration of disease were evaluated. SUBJECT AND METHODS: The present study was a cross-sectional study. Data was collected from all patients who visited the respiratory emergency department from March 20, 2020 to April 24, 2020 in the University Hospital. The outcome measures were body mass index, diet quality that was evaluated with a 16-item food intake questionnaire, and physical activity level that was assessed by the global physical activity questionnaire. RESULTS: Two hundred and six patients' data was analyzed. The results investigated that patients with lower levels of physical activity or lower MET.min/week were affected by a more severe form of the disease ( = 0.05 and  = 0.03, respectively). We found that patients with a healthier dietary pattern were affected by lower severity of illness ( < 0.05). CONCLUSION: It seems that increasing levels of physical activity may partly reduce the severity of COVID-19 disease. Some dietary patterns such as increasing fruit and poultry consumption as well as drinking less tea were correlated significantly with a less severe form of the disease. The results did not confirm previous concerns regarding a potentially harmful effect of smoking on the severity or duration of symptoms.