To evaluate whether bioimpedance analysis (BIA) is a useful tool for predicting basal metabolic rate (BMR), sex, age, height, weight, BMI, and single-frequency BIA variables (resistance index and phase angle) were assessed in 61 young adult non-diabetic obese patients (BMI >35 kg/m(2)). BMR was measured by indirect calorimetry. In both sexes BMR significantly correlated with weight, BMI, and resistance index. Using multiple regression analysis, the following prediction equations were derived: (1). considering individual characteristics: BMR (kcal/day)=780+11.4xweight (+221 for men); (2). including also BIA variables: BMR=- 96+8.4xresistance index+8.3xweight+82.5xphase angle. Thus, in young adult, severely obese individuals, BIA variables are significant predictors of BMR.