WEIGHT REGULATION: ENERGY BALANCE EQUATION AND CALORIES

What is the energy balance equation?

The balance between energy intake (in the form of calories) and energy output is called the 'energy balance equation'. To maintain body weight, the number of food calories ingested has to be balanced by the number of calories expended through exercise and resting metabolic rate. The majority of calories expended can be accounted for by the normal physiological energy requirements that enable healthy functioning of physiological systems and tissue repair. This energy expenditure is known as the resting metabolic rate (RMR) and can account for as many as 2000 kilocalories a day in an adult male; the other 500 kilocalories are expended as energy. A continuous intake of excess calories leads to weight gain; a continuous calorific intake deficit leads to weight loss.

What is a calorie?

The joule (J) is the standard SI unit of energy. A calorie is equal to 4.22 joules. One calorie is equal to the energy required to heat 1 L of water (1 kg) by 1°C, from 14.5 to i5.5°C. One calorie can therefore also be described as one 'kilogram calorie' or one 'kilocalorie' (kcal). The term 'calorie' is used interchangeably with the term 'kilocalorie'.

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