Different metabolic phases can be distinguished in critical illness, which influences nutritional treatment. Achieving optimal nutritional treatment during these phases in critically ill patients is challenging.

The current review aims to summarize the complex relationship between SARS-CoV-2 infection and nutritional status and the effects of malnutrition in terms of disease severity, patients’ recovery time, incidence of complications and mortality rate.

The cardiopulmonary exercise test (CPET) provides an objective assessment of ventilatory limitation, related to the exercise minute ventilation (VE) coupled to carbon dioxide output (VCO2); high values of VE/VCO2 slope define an exercise ventilatory inefficiency.

Nutritional and metabolic disturbances are observed in patients critically ill with COVID-19. At each step of the progression of the disease, ICU patients with COVID-19 should be carefully evaluated in terms of malnutrition risk and medical nutritional support.