People are malnourished if they are unable to utilize fully the food they eat, for example due to diarrhoea or other illnesses (secondary malnutrition), if they consume too many calories (overnutrition), or if their diet does not provide adequate calories and protein for growth and maintenance (undernutrition or protein-energy malnutrition).

Unipolar depressive disorders Hearing loss, adult onset Iron-deficiency anaemia Chronic obstructive pulmonary disease Alcohol use disorders Osteoarthritis Schizophrenia Falls Bipolar affective disorder Asthma Congenital abnormalities Perinatal conditions Alzheimer's and other dementias Cataracts Road traffic accidents Protein–energy malnutrition Cerebrovascular disease HIV/AIDS Migraine Diabetes mellitus 11.9 4.6 4.5 3.3 3.1 3.0 2.8 2.8 2.5 2.1 2.1 2.0 2.0 1.9 1.8 1.7 1.7 1.5 1.4 1.4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Unipolar depressive disorders Alcohol use ...[+++]disorders Hearing loss, adult onset Iron-deficiency anaemia Chronic obstructive pulmonary disease Falls Schizophrenia Road traffic accidents Bipolar affective disorder Osteoarthritis Asthma Perinatal conditions Congenital abnormalities Cataracts Protein–energy malnutrition Alzheimer's and other dementias Cerebrovascular disease HIV/AIDS Lymphatic filariasis Drug use disorders 9.7 5.5 5.1 4.1 3.8 3.3 3.0 2.7 2.6 2.5 2.3 2.2 2.2 1.9 1.8 1.8 1.7 1.6 1.6 1.6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Protein-energy malnutrition, for example, plays a major role in half of all under-five deaths each year in developing countries (WHO 2000).

Protein-energy malnutrition is defined as a range of pathological conditions arising from coincident lack, in varying proportions, of protein and calories, occurring most frequently in infants and young children and commonly associated with infections (84).

Oral absorption was slower in patients with proteinenergy-malnutrition and pellagra than in patients with anaemia or vitamin B complex deficiency patients and healthy controls.

Albumin is the most important plasma protein for binding of many drugs, but in protein-energy malnutrition hypoalbuminaemia results from decreased synthesis as dietary deficiency occurs.