ABSTRACT
Basic laws of thermodynamics in humans determine that if total daily energy expenditure (EE) exceeds daily energy intake (EI), a negative energy balance ensues and obesity reduction will follow. Of the three major components of EE ([1] resting metabolic rate, [2] the thermal effect of feeding, and [3] the thermal effect of physical activity [PA]), the thermal effect of PA is the most variable component of daily EE and can constitute from 15% to 30% of 24-hour EE.1 Indeed, a large portion of the marked variability of 24-hour EE among individuals, independent of differences in body size, is due to variability in the degree of daily PA.2 Thus, variation in daily PA and/or exercise will have a notable effect on daily EE and reinforces its importance as a primary determinant of energy balance and, hence, obesity.
