Advances in understanding and assessing malnutrition.
To describe the varying views on the pathophysiology of malnutrition in different populations and the definitions that result from these views. To propose an umbrella definition for different malnutrition syndromes and principles of assessment of nutritional state. At present, tacitly or openly inflammatory activity is considered to contribute to the malnourished state. The malnourished state, therefore, arises from a combination of inflammation and a disturbed nutrient balance (undernutrition or overnutrition). The undernourished category of malnutrition leads to loss of body cell mass, which, together with inflammation diminish host response and quality of life. On the basis of these findings, malnutrition may be assessed by estimating nutrient balance but, subsequently, to measure body composition (muscle mass), inflammatory activity (plasma albumin and C-reactive protein) and muscle endurance and force. Changes in muscle function in patients with chronic obstructive pulmonary disease are associated with changes in fiber composition. Few data exist in other malnourished states. There is an increasing acknowledgement of the fact that malnutrition is caused by disturbances in nutrient balance and inflammatory activity. This leads to changes in body composition and diminished function. An umbrella definition has been proposed including the pathogenetic factors, underlying the different malnutrition syndromes and dictating the methods to assess malnutrition.