[Definition, epidemiology and prognosis of undernutrition in adults].

DEFINITION, EPIDEMIOLOGY AND PROGNOSIS OF UNDERNUTRITION IN ADULTS Undernutrition is a pernicious and very frequent disease, particularly in hospitals (30 to 40% of adults) where it tends to worsen during the stay. The Covid-19 epidemic has further increased its prevalence. Its pernicious nature is that it is often considered as a symptom accompanying a pre-existing acute or chronic illness and not a disease in its own right.