TOTAL BODY POTASSIUM FAT FREE WEIGHT AND MAXIMAL AEROBIC POWER IN CHILDREN WITH ANOREXIA NERVOSA

Abstract

Body composition and aerobic work performance were studied in 5 boys and 10 girls with anorexia nervosa. The average ages of the children were 15.4 (boys) and 15.2 (girls) yr. Measurements of body composition included height, weight (W), body potassium (40K), skinfold thickness (SFT) at triceps and subscapularis, blood volume (BV) and femoral condylar and radioulnar breadths. From these measurements estimates of fat free weight (FFW), skeletal weight (S) and lean body mass (LBM) were made. Work performance was assessed by measurement of the maximal aerobic power (.ovrhdot.VO2 max). The patients lost on average 26% of their former body weight. The boys had on average > 7% of their body weight as fat compared with > 9% in the girls. The loss of weight was not solely due to loss of body fat, but could also be ascribed to a decrease in soft fatfree tissue. LBM or FFW could be estimated as well from SFT as from 40K. .ovrhdot.VO2 max averaged 1.43 1/min (35.1 ml/kg per min) in the anorexic boys and 1.24 1/min (33.2 ml/kg per min) in the girls and was associated with FFW and LBM. .ovrhdot.VO2 max was lower in relation to LBM than in healthy children of the same age. The emaciation in anorexia is directly attributable to loss of both fat and muscle and accounts in part for the reduction of aerobic power observed. An important factor may be the debilitating effect of starvation on the patient, particularly in its advanced and later stages, which reduces his/her level of habitual physical activity.