The Concept of CMR

An introduction to energy expenditure

Although it is beyond dispute that obesity is rising in westernized societies, data from the National Health And Nutrition Examination Surveys (NHANES I (1971-75) to NHANES III (2002-02)) reported by Kant and Graubard (1) did not show that Americans’ energy intake had increased. Dietary fat consumption even decreased over time. Although the apparent reduction in energy intake is controversial and the findings have been questioned, these results do suggest that the obesity epidemic might be due mainly to decreased energy expenditure, a characteristic of industrialized populations, rather than drastic changes in feeding behaviours and dietary patterns.

A key component of energy expenditure is resting metabolic rate (RMR). RMR is defined as the energy expended when an individual is lying and resting after sleep. RMR is linked to body size and lean body mass especially. Race and diabetes also affect RMR (2). In sedentary individuals, RMR is the most important component of daily energy expenditure, accounting for up to 60% of total daily energy expenditure. This percentage is lower in physically active individuals or highly trained athletes (3). The Figure depicts the components of energy expenditure in sedentary individuals, physically active individuals who do not exercise, and physically active individuals who exercise regularly.