ABSTRACT
Calories provide the raw materials for production of cellular energy. Cellular energy generation is maintained until death of the organism in starvation. Glucose in particular is a major energy source for fibroblasts and lymphocytes. Impaired glucose supply delays wound healing. Calories also provide the raw materials for building and repairing tissues. Cellular structures are composed of proteins, glycoproteins, glycosaminoglycans, membranes, and nucleic acids. Calories also trigger hormonal responses, especially insulin, glucagon, somatotropin, and intestinal neuropeptides. The estimation of dietary intake and energy expenditure can give an idea of whether an individual is consuming adequate calories to prevent weight loss, and, thus, malnutrition, at the time of estimation. Use of clinical laboratory analysis for determination of malnutrition has been helpful in hospital settings, but is of more dubious value in ambulatory outpatient settings. Measurement of levels of certain plasma proteins can yield information on short-term protein-calorie status.
