Energy Balance

Energy balance is the relationship between the energy a person obtains from food and beverages and the energy the body expends. When energy intake and expenditure are approximately equal over a given period, body energy stores remain relatively stable. When intake exceeds expenditure, the resulting positive energy balance increases stored energy, whereas a negative energy balance causes stored energy to be used .^1,2

Energy expenditure includes the energy required for basic physiological functions, physical activity, and the processing of food. Resting energy expenditure accounts for functions such as maintaining circulation, respiration, ion gradients, and cellular metabolism. Physical activity expenditure includes both structured exercise and other movement, while the thermic effect of food represents energy expended during digestion, absorption, and metabolism .¹

Energy balance does not need to occur within every meal or even every day. Energy intake and expenditure can differ substantially over short periods while remaining balanced over longer periods. Changes in body energy stores can also influence both appetite and energy expenditure. Energy balance is therefore a dynamic biological process rather than a moment-to-moment matching of energy consumed and energy expended .^1,2

Energy balance is related to, but not identical with, body weight. Changes in stored body energy generally contribute to changes in body mass, but body weight can also fluctuate because of changes in water, glycogen, and other components. Energy balance specifically describes the relationship among energy intake, energy expenditure, and changes in body energy stores .¹