Objective: To identify factors that contribute to the increased susceptibility and severity of COVID-19 in obese children and adolescents, and its health consequences. Sources: Studies published between 2000 and 2020 in the PubMed, MEDLINE, Scopus, SciELO, and Cochrane databases. Summary of findings: Obesity is a highly prevalent comorbidity in severe cases of COVID-19 in children and adolescents; social isolation may lead to increase fat accumulation. Excessive adipose tissue, deficit in lean mass, insulin resistance, dyslipidemia, hypertension, high levels of proinflammatory cytokines, and low intake of essential nutrients are factors that compromise the functioning of organs and systems in obese individuals. These factors are associated with damage to immune, cardiovascular, respiratory, and urinary systems, along with modification of the intestinal microbiota (dysbiosis). In severe acute respiratory syndrome coronavirus 2 infection, these organic changes from obesity may increase the need for ventilatory assistance, risk of thromboembolism, reduced glomerular filtration rate, changes in the innate and adaptive immune response, and perpetuation of the chronic inflammatory response. Conclusions: The need for social isolation can have the effect of causing or worsening obesity and its comorbidities, and pediatricians need to be aware of this issue. Facing children with suspected or confirmed COVID-19, health professionals should 1) diagnose excess weight; 2) advise on health care in times of isolation; 3) screen for comorbidities, ensuring that treatment is not interrupted; 4) measure levels of immunonutrients; 5) guide the family in understanding the specifics of the situation; and 6) refer to units qualified to care for obese children and adolescents when necessary.