The Importance of Energy Balance

Abstract

Globally, bodyweight and obesity are rising in both the developing and developed world. To maintain a stable bodyweight, energy intake must, over time, exactly equal energy expenditure, a state known as energy balance. an understanding of the physiologic control of energy balance may be useful for designing interventions to tackle the obesity epidemic worldwide. obesity occurs when the body's energy balance is positive (i.e. when energy intake exceeds energy expenditure). human physiology is biased towards maintaining energy balance at high levels of energy intake and expenditure. as a result, strategies to combat obesity should include a focus on increasing physical activity along with strategies for modifying food intake. an understanding of energy balance leads to the conclusion that prevention of weight gain should be easier than treatment of obesity. components of energy balance are interdependent, and weight loss requires major behaviour changes, which trigger compensatory decreases in energy expenditure that facilitate weight regain. Prevention of weight gain can be accomplished by smaller behaviour changes. in addition to being easier to sustain than larger behaviour changes, smaller ones produce less compensation by the energy balance regulatory system. it has been estimated that relatively small changes in energy intake and expenditure totaling 100 kcal per day could arrest weight gain in most people. interventions that advocate small changes have shown promising levels of success. KeywordsEnergy balance, obesity, physical activity The Concept of Energy BalanceThe concept of energy balance is based on the fundamental thermodynamic principle that energy cannot be destroyed, and can only be gained, lost, or stored by an organism. Energy balance is defined as the state achieved when the energy intake equals energy expenditure. This concept may be used to demonstrate how bodyweight will change over time in response to changes in energy intake and expenditure. When the body is in energy balance, bodyweight is stable. 9,10 humans take in energy through the intake of food and drink, and expend energy through the resting metabolic rate (RMR)-the thermic effect (TEF) of food and physical activity. The RMR is the energy expenditure required for maintaining normal body functions and homeostasis. The RMR is proportional to body mass, in particular fat-free mass. TEF refers to the energy required to absorb, digest, and metabolise the food consumed and typically accounts for 8-10 % of daily energy expenditure. The energy expended due to physical activity (EEact) accounts for energy that is expended in addition to the RMR and TEF, including voluntary exercise, shivering, postural control, and voluntary movement. it is calculated by multiplying the energy expenditure of an activity by the time spent performing it, and is the most variable component of energy expenditure. 10 The more sedentary the individual is, the lower the effect of physical activity. This may be as low as 100 calories per day, whereas elit...

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