Kinetic analysis of the thermic effect of food and its relationship to body composition in humans

The course of energy expenditure after a meal can vary widely with regard t o the slope of onset, amplitude, and duration of the thermic effect. The ai m of the present study was to explore the relationship between the thermic effect of food (TEF), as characterized by kinetic analysis of postprandial energy expenditure, body composition, and variables related to the metaboli c syndrome including central obesity, hypertension, and glucose tolerance. A total of 181 men and women (body mass index [BMI] range, 19.4 to 52.2 kg/ m(2)) were characterized for body composition, blood pressure, oral glucose tolerance, and energy expenditure after a test meal. Energy expenditure, a s measured by indirect calorimetry, was analyzed over a 6-hour period by 3- parameter curve fitting using equations derived from kinetics describing a biphasic reaction involving 2 consecutive first-order reactions (A -> B -> C). Apart from total thermic effect of food (TEFk), the curve also provided an estimate of time of peak (T-p) and amplitude of peak (A(p)) for each su bject. Multiple stepwise regression analysis with TEFk, A(p), and T-p as de pendent variables showed significant effects of sex, age, body weight, body fat, beta-blockade, and body composition on TEF curve parameters. Cluster analysis based on T-p shown 2 distinct clusters with significant difference s in age and body fat mass. This study shows that kinetic analysis of postp randial energy expenditure can be used to examine the determinants of the t ime course of the thermic effect of food in man. Copyright (C) 2000 by W.B. Saunders Company.