Defect in thermoregulation in malnutrition reversed by weight gain. Physiological mechanisms and clinical importance.

Previous studies in infants and in the elderly have shown that a low body weight is associated with a defect in thermoregulation and an increased risk of hypothermia. In the present study, thermoregulatory responses to a cooling stimulus were measured in 10 young and middle-aged patients who lost at least 10 per cent of their body weight during illness. Investigations were performed before and after restoration of body weight (mean weight gain 7.2 kg, SE 1.2 kg, p less than 0.001). The cooling stimulus was provided by a special suit perfused with water at 28 degrees C and then at 23 degrees C. Before weight gain, there was no increase in metabolic rate in response to cooling, despite a fall in core temperature. Following weight gain, the thermogenic response to cooling was restored towards normal. Peripheral vasoconstriction, the principal mechanism for heat conservation, was similar before and after weight gain. The thermogenic response to an infusion of adrenaline (25 ng/kg/min) was not abolished by weight loss, suggesting that the defect in cold-induced thermogenesis following weight loss is due to a change in central control mechanisms of thermoregulation, and not to tissue unresponsiveness. The phenomenon of abnormal thermoregulation following weight loss and the return to normal with subsequent weight gain may be clinically important, particularly in the elderly, since quite small falls in core temperature may impair both neuromuscular coordination and cerebral function.