[CITATION][C] Energy expenditure and fuel selection in biological systems: the theory and practice of calculations based on indirect calorimetry and tracer methods

M Elia, G Livesey - Metabolic control of eating, energy expenditure and …, 1992 - karger.com
M Elia, G Livesey
Metabolic control of eating, energy expenditure and the bioenergetics of …, 1992karger.com
All living organisms use fuels to maintain their life cycles. Consequently the source and the
fate of fuels used are of fundamental importance to biology, nutrition and biochemistry. A
number of techniques for measuring fuel selection and utilization have been developed, but
precise interpretation requires detailed understanding of the assumptions, and the optimal
use of calculation procedures. The measurement of energy expenditure in mammals
originated in the late 18th century when Lavoiser noted how quickly blocks of ice were …
All living organisms use fuels to maintain their life cycles. Consequently the source and the fate of fuels used are of fundamental importance to biology, nutrition and biochemistry. A number of techniques for measuring fuel selection and utilization have been developed, but precise interpretation requires detailed understanding of the assumptions, and the optimal use of calculation procedures. The measurement of energy expenditure in mammals originated in the late 18th century when Lavoiser noted how quickly blocks of ice were melted by heat released from animals and how this was related to the rate of oxygen consumption. Direct calorimeters are now fitted with sophisticated heat exchange systems and other equipment that take into account the heat loss due to evaporation [1]. Consideration of the stoichiometries of fuel oxidation have allowed the development of classical indirect methods of calorimetry. These methods depend on the estimation of heat production from measurements of oxygen consumption, carbon dioxide production, and sometimes the excretion of other substances, such as urinary nitrogen, methane and hydrogen. Although indirect calorimetry is now used much more frequently than direct calorimetry, the direct method has played an important role in validating the indirect methods. In its turn, classical indirect calorimetry has been used to validate isotopic tracer methods which involve estimates of energy expenditure from CO2 production. One of these methods is a simple isotope dilution technique which uses labelled bicarbonate [2, 3]. Another is a dual isotope technique which involves estimation of CO2 production after administration of water labelled with both 2H and 18O [4,
Karger