The potential use of the labelled bicarbonate method for estimating energy expenditure in man.

Two tracer methods have been used to assess energy expenditure in animals and humans: the doubly-labelled-water method (for animals Lifson et af . 1955; for humans Prentice, 1988; Coward, 1988) and the labelled bicarbonate method (for humans present paper; for animals Corbett er al. 1971). Whereas the doubly-labelled-water technique attempts to provide information about the energy expenditure over long periods of time (2-3 weeks in adult human subjects), the bicarbonate method attempts to provide information about shorter periods of time (hours to days). Both techniques assess carbon dioxide production, and therefore it is necessary to relate COZ production to energy expenditure. These aspects will be discussed separately.