[Energy expenditure: method employed]

Energy expenditure (or energy needs) corresponds to the energy required for the body to work under all circumstances. This is the energy that should be taken (with food) to maintain energy balance, i.e. the constancy of body weight. Energy is expended at rest (referred to as basal or resting metabolic rate), when food is consumed (diet induced thermogenesis) and with physical activity. In obese people, energy expenditure is increased because of the proportion between body mass and energy expenditure. There is no definite proof that there is a metabolic defect in obese persons by which energy expenditure would be lower than expected for body mass. Hence obesity can only be the result of a positive energy balance. Energy expenditure can be measured by indirect calorimetry or estimated with equations. These equations use factors as weight, age, gender and sometime height. These equations are generally valid although there is a need for more validation studies. This paper also describes in which clinical circumstances the measurement or the estimate of energy expenditure are useful for the care of obese patients.