The use of surface area and of body-weight as standards of reference in studies on human energy expenditure.

In assessing the nutritional status of populations, it is becoming increasingly common to measure not only the total food intake but also the energy expenditure of groups of individuals. I t is often difficult to compare the results obtained by different authors in such studies of energy expenditure because of the diverse ways in which these results may be expressed. The metabolic cost of a period of work, or of any particular activity, may be given as gross Cal. or net Cal.; net Cal. may involve a deduction for basal metabolism (B.M.R.) or for specific dynamic action (s.D.A.) or for both. These results may then appear as Cal./h or Cal./min; they may be expressed as Cal./m2 body surface area or as Cal./kg body-weight; they may be Cal. per gross body-weight or per fat-free body-weight. For example, Carpenter & Benedict (1909) express their results as gross Cal./h. Cathcart & Orr (1919) express theirs as gross Cal./h and gross Cal./m2/h. Orr & Leitch (1937-8) list the energy expenditure of general activities (e.g. knitting, washing, shoemaking, mining) as Cal./h after deduction of the expenditure in basal metabolism and after subtraction of 10% of the energy expenditure as due to S.D.A. Granati & Busca (1941) give energy expenditure for a specific activity as Cal./Io min work with a deduction for the metabolism of rest. Marro, Milani & Vigliani (1954) use gross Cal./m2/h. Lehmann, Muller & Spitzer (1950) use net Cal. with a deduction for B.M.R. Christensen & Hogberg (1950) and Christensen (1953) quote results as gross Cal./min. Insull (1954) uses gross Cal./min. Buskirk, Kreider, Brebbia, Morana, Daniels, Welch, Mann, Insull & Friedemann (1956) express results as Cal./kg bodyweight/h and as Cal./m2/h. Welch, Marcinek, Buskirk & Iampietro (1957) give results as net Cal./min with deductions for B.M.R. and S.D.A. Therefore, before data from different sources can be compared much recalculation must be done. Passmore & Durnin (1955) had this difficulty when they drew up tables to express energy expenditure in different activities in a consistent manner. There would often appear to be little reason for this diversity. The present paper discusses this problem with especial regard to the use of surface area and of body-weight as the particular standard of reference.