Since the classical experiments by Lavoisier and Laplace
in 1783, energy metabolism remains the central tenant
of human nutrition. Basal metabolic rate (BMR) was introduced to describe energy expended at rest in contrast
to energy expended during physical activity and has been
described as the “minimal rate of energy expenditure
compatible with life” [1]. It represents the energy required
for maintenance, necessary to sustain and maintain the integrity of vital functions and is mainly determined by
the amount of lean tissue. Generally, BMR represents
60–80 % of total daily energy expenditure (TDEE) [2, 3].
In the 1985 FAO/WHO/UNU report on human energy
and protein requirements, the use of energy expenditure
rather than food intake was proposed to calculate energy
requirements and additionally, it was proposed that TDEE
can be expressed as multiples of BMR, defined as physical
activity level (PAL) [3–7]. This approach to estimate energy requirements necessitates the accurate estimation of
BMR in populations of different ethnicities and body
weight and living under various environmental conditions.
Indirect calorimetry, which is based on the measurement of oxygen consumption and carbon dioxide