Abstract
Even a small daily positive energy balance leads to weight gain over a period of a few years. Understanding changes in the energy balance is important for preventing obesity. The purpose of this review is to discuss the variable factors involved in total daily energy expenditure (TDEE) in humans. TDEE comprises the resting metabolic rate (RMR), diet-induced thermogenesis (DIT), and physical activity energy expenditure (PAEE). RMR comprises the largest component (~60%) of TDEE. DIT accounts for approximately 10% of TDEE, and PAEE approximately 30%. A large part of the variation in RMR can be explained by body composition and body size. The primary determinant of DIT is meal size and composition. Body size and aging are also potential factors of variability in DIT. PAEE can be further categorized into exercise-induced energy expenditure (EXEE) and non-exercise activity thermogenesis (NEAT). EXEE mainly depends on body size, and exercise intensity and duration. In addition, excess post-exercise oxygen consumption following exercise is thought to have a significant impact on total EXEE. Based on a review of published studies, however, it is clear that in most individuals, EXEE is not a large contributor to TDEE. On the other hand, NEAT has the greatest impact on variation in TDEE, which varies by up to 2000 kcal per day between people of similar body size. In summary, there are several factors involved in the contribution of each component of TDEE. Although each factor contributes to small changes in TDEE, the sum of these influences may induce a large energy imbalance.
