CHANGES IN THE BASAL METABOLIC RATE OF THE MALNOURISHED INFANT AND THEIR RELATION TO BODY COMPOSITION

Abstract

The basal metabolic rate (BMR) was studied by a closed circuit system in 36 infants suffering from and recovering from severe protein malnutrition. In 9 cases concomitant studies were made of total body water by tritium dilution. In most cases, the initial O2 consumption tended to be subnormal in relation to calculated surface area but was approximately normal in terms of body weight and of body solid mass. However, owing to an abnormal preponderance of the most metabolically active organs, notably the brain, this finding suggests a true depression of respiratory activity in the individual organs. In a few marasmic cases the BMR was initially increased both in terms of body weight and surface area. Serial tests showed a dramatic rise in total O2 consumption, often more than 2-fold, during the early weeks of recovery. This rise was followed by a plateau level which was maintained regardless of variable gains in weight. Total O2 consumption at this plateau level approached the normal for a healthy child of the same age. Body weight did not increase unless the caloric intake consistently exceeded the BMR by 60 - 85 cals per kg./day. The greater the weight deficit, the higher was the BMR during recovery and the higher the caloric requirement for weight gain. It is suggested that the limit of 02 uptake in recovery may be determined partly through the restoration of normal activity in the organs which are least reduced in relation to age, and partly through the factor of the mean "metabolic potential" of the individual cell. Cell number per unit of tissue mass is increased in the active tissues of the malnourished growing animal. The mean respiratory activity/cell is therefore much reduced initially but may approach the normal during recovery.