ABSTRACT
The basal metabolic rate (BMR) and thermic effect of food (TEF) collectively contribute 70%–80% of daily energy expenditure (EE) in the majority of humans (with low to moderate physical activity). As such, BMR and TEF are of central importance to establishing daily energy requirements for public health and clinical nutrition use. Further, research on their putative roles, which is often controversial, is of paramount significance in identifying the etiology of metabolic diseases, such as obesity, and in determining the efficacy of anti-obesity therapies.
This chapter examines the principles underlying measurement of EE and macronutrient oxidation rates by indirect calorimetry, the advantages of indirect over direct calorimetry, the inherent assumptions and methodological approaches for assessing BMR and TEF, the distinction between the use of the terms BMR and resting metabolic rate (RMR), and the distinction between TEF assessed by the hood (canopy) system and that assessed in a whole-body respiration chamber. It then analyzes the endogenous and exogenous factors that contribute to intra- and interindividual variability in BMR, RMR, and TEF, including the impact of macronutrient composition, obesity status, overnutrition, undernutrition, and therapeutic dieting with implications for interindividual susceptibility to obesity and obesity relapse.
