Studies on Human Postprandial Thermogenesis

Human energy demand is composed of three factors: basal (resting) metabolic rate (65–70%), physical activity (approx. 20%) and heat-generating (thermogenic) effect of a meal (approx. 10%) also referred to as postprandial thermogenesis. (Delany and Lovejoy, 1996). A large body of research have already assessed the impact of various factors on postprandial thermogenesis and these involved hormonal and neurohormonal indices (insulin, adrenaline and noradrenaline) as well as biological factors (age, body weight, physical capacity). Although all of them are highly complex and interdependent, they have so far been analyzed and estimated independently. The present study concentrates on complexity and interactions of major factors affecting an increase in metabolic rate triggered by food intake. Food consumption leads to an increase in the metabolic rate. In literature the phenomenon is referred to by a range of terms: post-prandial thermogenesis (PPT) diet-induced thermogenesis (DIT), specific dynamic action of food (SDA), thermic effect of meal (TEM), thermic caloric response to food (TRF) (Houde-Nadeau et al., 1995; Glick, 1990; McCarter, 1995). Thermogenic effect of glucose (TEG) seems to be as adequate a term because human body response to glucose intake was a frequent subject of numerous previous studies in this scientific area. Metabolic rate increase after a single meal typically remains for several hours (Schutz et al., 1985; Blaxter, 1989). The metabolic rate rises with the amount of energy content of food but it increases to a different degree depending on food constituents. The fastest increase is triggered by carbohydrates consumption whereas protein intake causes the effect to last longest. The strongest thermal effect is produced by proteins, followed by carbohydrates and fats (Johnston et al. 2002, Westerterp, 2004). Resting metabolic rate in people on a high-