Obesity as an important risk factor for COVID-19 severity
Obesity has consistently been associated with increased COVID-19 severity, hospitalization rates and mortality, although the magnitude of the relation is still unclear as data are heterogeneous, due to different study protocols and populations [1–6].
The very large database of OpenSAFELY study examined more than 10,000 deaths in the UK and compared to over 17 million people from the UK Biobank. In this study, obesity was divided according to BMI: 30–34.9, 35–39.9 and over 40 kg/m2 or more, and these ranges were associated with a 1.23, 1.81 and 2.66 increased in risk of death [3]. Other studies found higher rates of hospitalization and mechanical ventilation in individuals with obesity [2, 5], and one meta-analysis found a 2.31 increased risk of COVID-19 complications in those with obesity diagnosis [3]. Moreover, the impact of the disease seems to be even greater in younger populations, which led to some authors to propose that “obesity shift severe COVID-19 to younger ages” [6].
The mechanisms by which obesity is associated with severe COVID-19 are still unknown, but several have been proposed [1, 2, 5]: increased inflammation, with enhanced production of cytokines; increased risk of microthrombosis; respiratory dysfunction (as decreased pulmonary expandability and cardiorespiratory fitness); technical difficulties in intensive care units (challenging orotracheal intubation and eight limits in imaging exams, less benefits of prone position); more prolonged viral shedding; and increased risk of other comorbidities associated with worse prognosis (as type 2 diabetes, hypertension, sleep apnea and cardiovascular disease). Likely, many of those factors are closely linked to insulin resistance and visceral fat and improving insulin sensitivity could hypothetically reduce risks [1, 7].