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 to the slope of onset, amplitude, and duration of the thermic effect. The aim 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 metabolic 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/m2) were characterized for body composition, blood pressure, oral glucose tolerance, and energy expenditure after a test meal. Energy expenditure, as 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 (Tp) and amplitude of peak (Ap) for each subject. Multiple stepwise regression analysis with TEFk, Ap, and Tp as dependent variables showed significant effects of sex, age, body weight, body fat, beta-blockade, and body composition on TEF curve parameters. Cluster analysis based on Tp shown 2 distinct clusters with significant differences in age and body fat mass. This study shows that kinetic analysis of postprandial energy expenditure can be used to examine the determinants of the time course of the thermic effect of food in man.