The scientific basis of nutritional assessment.

Nutritional assessment is the essential first step in the adequate nutritional care of a patient. Simple bed-side impressions of nutritional status or change with therapy are invariably erroneous (Walesby et al., 1979) and are to be deprecated. Recent surveys (Bollet and Owens, 1973; Bistrian et al., 1976; Hill et al., 1977; Letsou, Connaughton and O'Donnell, 1977; Willicutts, 1977) have shown that up to 50% of patients in hospital were moderately or severely malnourished. Malnutrition may have a profound influence upon clinical practice. Acute weight loss of more than 40% is invariably fatal while degrees of wasting are associated with increasing mortality and morbidity. Such depletion results in poor wound healing and callus formation, immunological depression, disordered coagulation, reduced enzyme synthesis, altered drug metabolism, decreased tolerance to radiotherapy and chemotherapy, and prolonged convalescence after surgery. The formulation of an appropriate feeding regimen for the wasted patient can only be done after accurately establishing the nature and degree of depletion. However, a recent study (Ray and Dickerson, 1979) has shown that clinicians faced with many available tests are both uncertain about those most appropriate, and confused as to the ultimate aim of management. Brozek and Henschel (1961) described how Rubner in 1902 conceived the idea of an oxidizing protoplasmic mass as the component of the body responsible for energy consumption and chemical and mechanical work performed. Moulton (1923) reinforced this concept, showing that body fat was a variable quantity and emphasized the constant composition of the lean body weight; which on analysis was hydrated and both nitrogenand potassium-rich in contrast to neutral fat. Since then Kinney, Lister and Moore (1963) have demonstrated that resting energy expenditure was directly related to the size of the lean body mass.