Caloric undernutrition occurs primarily as a result of a limited food supply, exemplified by semi-starvation and starvation, and secondarily as a consequence of many pathologic states, particularly those associated with an increase in metabolism or with anorexia or gastrointestinal disturbances. The loss of potential calories in diarrheal diseases, especially in steatorrheas, may be extensive. In diabetes mellitus, glycosuria is a manifestation of caloric loss.
Caloric balance can be maintained over a fairly wide range of body weight and caloric intake in a given individual. A continued loss of weight beyond 10% may be considered evidence of caloric deficit. Weighing a patient at frequent intervals is the best single method of deter-mining caloric balance although fluctuations may represent changes in fluid rather than in metabolic mass, especially in acutely ill patients.
The primary findings in caloric undernutrition, in addition to weight loss, are wasting of muscles, weakness and lethargy. Nitrogen balance is negative and deficiency of protein complicates the clinical picture. The previous state of nutrition, the character of the diet and the manifestations of primary disease, when such is present, influence findings.
In severe starvation, apathy, weakness and wasting of muscles become extreme and the patient literally appears to be nothing but skin and bones. Mental and emotional changes are common and are reflected in behavior. Pigmentary changes in the skin have been observed. Circulatory findings include bradycardia, hypotension, reduced peripheral circulation and decreased venous pressure. The body temperature is lowered and there is a decrease in the reactivity of the organism to various stimuli. Neurological examination often shows diminished or abolished deep tendon reflexes but sensory mechanisms are maintained in most instances. Signs of depressed function of the endocrine system, particularly of the sex glands, are common, amenorrhea, sterility and loss of libido being frequent findings. The patient looks, feels, and acts pre-maturely old. Polyuria, increase in fluid intake and salt hunger are often observed. Osteomalacia is an occasional finding in prolonged starvation. Edema is frequently en-countered and may mask the extent of decrease in body weight. If protein deficiency is severe, the edema may be even more extensive and anemia, often of macrocytic type, may be present.
Signs of vitamin deficiency occur only if the diet has been deficient in these factors. Starvation, as observed in concentration and prisoner of war camps, particularly in the Orient, was accompanied in many instances by peripheral neuropathies, retrobulbar neuritis, deafness, encephalopathy and other neurologic syndromes. Some manifestations responded to therapy with B complex vitamins while others were unaffected.
In severe prolonged undernutrition, basal metabolic rate declines; the decrease in basal oxygen consumption applies to active metabolizing tissue as well as to the whole organism. The fasting blood sugar may be low and tolerance for glucose diminished. In semi-starvation experiments with human volunteers, blood pyruvate rose to abnormally high levels after exercise (19). Studies of body composition in these experiments, in which an aver-age of 16 kg. in weight was lost in 24 weeks, indicated no significant change in bone mineral or in extracellular fluid, a marked decrease in body fat and a lesser but significant decrease in active metabolizing tissue. On a percentage basis, the body contained less fat and muscle but more water. This excess fluid may explain, at least in part, the occurrence of starvation edema. For a review of the biochemical and physiological changes in starvation, reference is made to the compilation published by Keys and associates.
In caloric undernutrition, the extent of the weight loss is an important factor in prognosis. If the loss is 30% or-‘ less in previously healthy persons, full recovery may occur with proper care. A loss of more than 40% is serious, al-though recovery is at times possible.
Caloric undernutrition which is secondary to disease may be manifested by many of the findings just described, in addition to the signs characteristic of the primary pathologic process. Another finding worthy of emphasis is that starved persons are poor surgical risks. Extensive loss of weight may lead to altered hepatic function, contracted blood volume, reduced capacity to control infections and impaired wound healing. Furthermore, it is difficult to determine when rehabilitation is sufficiently advanced to undertake surgery.
Knowledge of the residues of serious undernutrition, the late or permanent effects, is limited. Children seem to recover completely from caloric restriction if the duration is not more than a year or two. Residues of severe or protracted malnutrition, in formerly healthy soldiers who had been in prison camps, have included excessive fatigue, weakness, inability to maintain proper weight, general “nervousness,” excessive sweating, paresthesias, visual defects including optic atrophy, hernias, cardiac and gastrointestinal complaints and osteopathy. There is little knowledge of the possible effects of malnutrition or its residues on susceptibility to, or on the course of, other diseases. Simple undernutrition tends to have a favorable influence on diabetes and a detrimental effect on tuberculosis. Psychological residues of starvation are probably of great importance but have received little study.