The Role of Diet and Physical Activity in Shaping COVID-19 Severity: Design, Validation, and Application of a Retrospective Questionnaire

After the global challenges posed by COVID-19, researchers strived to identify risk factors for severe cases, which lead to various complications—including death. Lifestyle modifications, such as implementing a healthy diet and recommended physical activity, have been shown to be protective against severe COVID-19 cases. Despite an association of a plant-based diet with reduced COVID-19 severity, specific dietary characteristics have not been identified. Also, the methodology for measuring physical activity is variable, with studies overlooking the intensity or the habit components of physical activity. To bridge this gap, our study designed, validated, and applied a retrospective questionnaire with aims of exploring the relationship between lifestyle factors, specifically diet and physical activity, and severe COVID-19. We considered the intensity and years of physical activity habit, which is a limitation of other questionnaires. Results reveal associations of age and BMI with severe COVID-19. An excessive sugar diet was found to be associated with severe COVID-19 and increased symptom duration. We also observed an inverse relationship pattern of moderate- and vigorous-intensity physical activity across case severity, which is absent in walking physical activity. This study lays a foundation for research aiming to identify lifestyle factors that prevent severe COVID-19 cases.