Energy balance and its components: implications of intra- and inter-individual variation on energy intake and expenditure

Abstract

Energy balance in human body undergoes constant change, leading to a change in the weight and body composition throughout life. Energy balance at a particular time point is influenced by the psychological, physiological, sociological, and environmental factors of that moment. In addition, the regulation of homeostasis continuously monitors and maintains the energy balance; however, it complicates the identification of factors influencing the energy balance. For understanding these factors, creating a model with comprehensive factors and testing it among a substantial number of individuals for dynamic changes in the energy balance may be warranted. However, till date, to the best of our knowledge, no studies report on comprehensive modeling, including homeostasis and the other factors. Thus, at this moment, summarizing previous studies for further research is required. Accordingly, this review summarizes 1) the basic factor of energy expenditure and intake; 2) interactive relationship between energy expenditure and intake; and 3) energy expenditure and intake during dynamic changes in the body weight caused by events such as overfeeding, underfeeding, growth and aging, and pregnancy.