NUTRITION IN SPORT

TDEE. However, there are a variety of factors
that may increase energy expenditure above
normal, such as cold, fear, stress, and various
medications or drugs. These factors are referred
to as adaptive thermogenesisand represent a tem-
porary increase in thermogenesis that may last
for hours or days, depending on the duration
and magnitude of the stimulus. For example, a
serious injury, the stress associated with competi-
tion, going to high altitudes, or the use of certain
drugs may all increase RMR.

Factors that influence RMR

It is well documented that RMR is influenced by
gender, age and body size, including the amount
of FFM and fat mass. These four variables gener-
ally explain about 80% of the variability in RMR

(Bogardus et al. 1986). Since FFM has a high

rate of metabolic activity, any change in FFM

would dramatically influence RMR. In general,

males have higher RMRs than females because

they usually weigh more and have more FFM.

However, Ferraro et al. (1992) found that females

have a lower RMR than males (approximately

100 kcal less per day) even after differences in

FFM, fat mass and age are controlled. Age is

another variable known to influence RMR. It is

estimated that the decline in RMR is less than

1–2% per decade from the second to the seventh

decade of life (Keys et al. 1983).

It is now known that RMR also has a genetic

component. This means that within a family

members may have similar RMRs. Two studies

illustrate this phenomenon. Bogardus et al. (1986)

found that family membership could explain

the overweight athlete 473

% of daily energy expenditure

100

25

75

50

Amount/composition

of food (hormones/SNS)

SMR

BMR

Arousal

Thermic effect

of food

SPA

Unrestricted

activity

• 
  


• 
  


• 
  


• – – – – – –

Determinants

Intensity

Duration

Body weight

Genetics/SNS?

Fat-free device

Fat mass

Age

Sex

Genetics

Hormones/SNS

Methods

Ventilated hood

Respiratory chamber

Doubly labelled water

0

Fig. 35.3Components of daily energy expenditure in humans. Daily energy expenditure can be divided into three
major components: (i) the basal metabolic rate (BMR) (the sum of the sleeping metabolic rate (SMR) and the energy
cost of arousal), which represents 50–70% of daily energy expenditure; (ii) the thermic effect of food, which
represents approximately 10% of daily energy expenditure; and (iii) the energy cost of physical activity (the sum of
spontaneous physical activity (SPA) and unrestricted/voluntary physical activity), which represents 20–40% of
daily energy expenditure. The major determinants of the different components of daily energy expenditure, as well
as the methods to measure them, are presented. SNS, sympathetic nervous system. From Ravussin and Swinburn
(1993).