Physical activity as a mediator of the association of body mass index change with anxiety/depression symptoms in Brazilian adults during CoVID-19

Background: the COVID-19 pandemic has impacted people’s behaviors and mental health around the world. Aim: to verify the mediating role of physical activity (PA) level in the relationship between body mass index (BMI) and anxiety and depression symptoms. Methods: this is a cross-sectional study with Brazilian adults aged ≥ 18 years (n = 2,000, 59.6 % women) selected by the nonprobabilistic snowball method through digital means of communication (WhatsApp®, Telegram®, Facebook®, Twitter®, e-mails). Linear regression models were fitted for PA level mediation analyses in the relationship between BMI and anxiety/depression symptoms. Results: significant differences were found between the active/not overweight group and the other three groups (active/overweight, insufficiently active/not overweight and insufficiently active/overweight [p < 0.001]) for anxiety/depression after adjusting for age, gender, chronic diseases, alcohol consumption, and smoking. When testing the mediating role of daily PA in the association between BMI and anxiety/depression symptoms, BMI was negatively associated with daily PA in the fi rst regression equation (p < 0.001); in the second, BMI was positively related to anxiety/ depression symptoms (p < 0.001); and in the third, daily PA showed an inverse relationship with anxiety/depression symptoms (p < 0.001), and although BMI remained negatively associated with anxiety/depression symptoms, these associations maintained their statistical significance. Conclusions: the results suggest that the effect of BMI on anxiety and depression was partially mediated by daily PA.