Estimating data1’2 A. E. Dugdale,

fat body M.D.,

F.R.A.

CF.

ABSTRACT boys

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J. Clin.

Nuir.

32: 2400-2403,

Journal

of Clinical

Nutrition

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anthropometric

M.Sc.

been

4 to 19 years

but the addition of skinfold errors in the estimates. The

A reasonable layer of subcutaneous fat in children is aesthetically pleasing as well as providing a concentrated and portable source of energy. However, the estimation of the amount of body fat is not easy. There is no direct method of measuring body fat in vivo and all indirect methods have defects. Durnin and Rahaman (I) and Cramwinckel et al. (2) have based their estimates of fat body mass (FBM) on body density. Because body density is not a suitable measurement for routine clinical use, they have developed regression equations based on the sums of several skinfold thicknesses to obtain a clinical approximation to their density-derived estimate. Brook (3) used the measure of total body water to calculate lean body mass (LBM), and from these results modified the equations of Durnin and Rahaman (1) to calculate FBM. More recently, the development of whole-body scintillation counters has made possible the estimation of 40K (4) and equations have been constructed to derive the LBM from the 40K measurement (5). With the 40K-derived LBM as a standard, equations for estimating LBM and FBM from anthropometric measurements have been calculated. Reba et al. (4) have used height and weight in their estimating equations, while Burmeister and Fromberg (6) used skinfold thicknesses alone. Lohman et al. (7) showed that the use of weight as well as skinfold thicknesses in the regression equations gave a better estimate of FBM than skinfold thicknesses alone, but their series covered only boys. In their 1970 paper, Burmeister and Fromberg (6) have given the raw data on which 2400

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1979.

their equations were based. We have recalculated the estimating equations from their data and by including weight and height as well as skinfold thicknesses have considerably increased the accuracy of the estimate of fat mass. Methods The measurements given by Burmeister and Fromberg (6) have been used as the data base. Weight, height, and skinfold thickness at nine sites and 441K measurements have been reported on 77 boys and 86 girls ranging in age from 4 to 19 years old. In another paper, Burmeister (5) has derived a formula for the calculation of LBM from the 40K value and the body surface area. The formula is: LBM = 11.9 40K/39 +6.045 where LBM = lean body mass in kilograms = millequivalents of #{176}K in the whole body S = body surface area in square metres using the Du Bois and Du Bois (8) formula FBM is obtained by subtracting LBM from total body mass. The appearance of surface area on the right side of the equation suggests a circular process with body mass and height being used to derive LBM. However, the surface area is used in the calculation of the extracellular fluid, and contributes littleto the variance in the LBM. We have used standard multifactorial linear regression methods to find which anthropometric factors give the best estimate of the calculated FBM. Equations have been developed with both untransformed and log-transformed data. As well as calculating the SD in the usual manner, we have examined the differences between the #{176}K-derived FBM and the FBM estimated from the

‘From the Department of Human Nutrition, London School of Hygiene and Tropical Medicine, Keppel Street (Gower Street), London WC1E 7HT, England. 2 reprint requests to: Dr. A. E. Dugdale, University Paediatric Unit, Mater Children’s Hospital, Mater Hill, Queensland, 4101, Australia. 32:

DECEMBER

1979, pp. 2400-2403.

Printed

in U.S.A.

ESTIMATING

FAT

regression equations in individual cial attention to those where there between the two estimates.

BODY

MASS

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children paying spewas a large difference

When multifactorial linear regression equations were calculated for boys and the estimated FBM compared with the 40K-derived FBM in individual children, good agreement was found in boys with a height of less than 150 cm, but in taller boys there were wide variations. One-hundred fifty centimeters is the 50th percentile height for boys 121/2 years old (9). The pubertal growth spurt that occurs about this height and age is associated with changes in body proportions and these changes may account for the variability. As there were only 15 boys in the series taller than 150 cm, reliable multiple regression equations could not be calculated. For girls less than 140 cm in height, the SD of the estimated FBM was similar to those for boys, but when taller girls were included in the estimating equations, the SD of the estimates increased considerably. Puberty in girls occurs when they are about 140 cm tall, and it appears that in girls, as in boys, the differing body proportions after puberty need separate estimating equations. As there were 30 girls in the series with heights