Human Energy Expenditure Studies in the National Institute of Arthritis and Metabolic Diseases Metabolic Chamber

Abstract

A brief description and graphic portrayal of the Metabolic Chamber facility and associated instrumentation have been presented. In a reinvestigation of one phase of the classical work of Rubner³ on specific dynamic effect, it was found that the increment in heat production associated with eating a 1,000 kilocalorie meal (40 per cent of kilocalories was protein) and the increment associated with exposure to cold showed summation when human subjects were fed while resting in the cold. The two dogs studied by Rubner reacted differently; heat produced after eating meat simply replaced the production of heat that would normally have occurred with exposure to cold. The dogs apparently shivered less after eating, and their critical temperature was lowered (environmental temperature at which shivering and elevated heat production is first observed). In contrast, no change was observed in the shivering response in our human subjects after they ate in a cold environment. Changes in metabolism during the night hours were demonstrated by continuous determinations of oxygen consumption on two women who slept in the Chamber. The results suggest that an energy expenditure value equal to basal would be more appropriate to apply in estimates of twenty-four hour energy expenditure than a value of basal minus 8 or 10 per cent. A relationship between the level of oxygen consumption for the night hours and the basal rate was suggested; if night time metabolic rate was high, so also was the basal rate. Although the depth of sleep is frequently greatest during the first hour or two after retiring, a relatively high oxygen consumption was routinely observed during this period. Continuing SDE and repayment of oxygen debt, incurred during the preparation for bed, may be responsible for this observation.