body fat in adolescent boys
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72 SUTRITION REVlE\\'S [T'ol. 22, N o . J
eclciii:r ~ e i v thc priiici1):rl I):itliological find- ing>. How\.cvc~~, tlic authors did not feel that these lwionh alone u-ere sufficient to causc the infant dcatlis. Congenital heart defect* and idiopathic inyocarditis were prcsent in four of tlic paticnts, and it is poshible that t h e w conditions were rchponsiblc for their deaths.
The re\ults of tlic. mitibody testing proved to be coinpletely negativc. In only one of tlic 33 cabes W N S a positive result obtained with tlic capillary precipitins procedure. Heiiiagglutination titcr was siinilar for the group suffering budden death to tliat found in a group of 67 controls of tlie same age. Values rangctl froin 1css than ten to greater than 300.
The failure to find any :wociation h- tween sudden unrxpcctcd dcath of tlic in- fanth and tlic prestncc of inilk iintihotlies in the serum cabth boiiie doubt 011 thc vicw that inilk hypersensitivity is a major cause
of sudden unexpected death, but papers sug- gesting that inilk is a factor receive con- siderable publicity, which in turn tends to confuse the mother who is feeding her infant a cows' inilk formula. The magnitude of this problem is such that continued efforts should be inade to define clearly the reason or reasons for these deaths.
Researchers in this area should be par- ticularly careful in their manner of publish. ing results. The general public is quick to seize upon medical claims promoted througli the daily newspaper. The average mother mould find i t difficult to prepare suitable formulas if all cows' milk preparations were eliminated, and i t is not safe to expect that she would consult her physician before mak- ing :i change in the diet of her infant. Even if d i c did, lie might hc unable to answer all Iicr questions, for news stories often art printed hefore publication of the scientificl paper on which they are based.
BODY FAT IN ADOLESCENT BOYS
Measurements of total body water, body densi ty , a)id sitbculrrnrotrs ti\suc [hack- ness all point to decrensing adzposity diclrng this ngc p ( J 7 t o d .
Much attention has been devoted in re- cent years to the subject of fat content in adult man ( A . Keys and .J. Brozek, Physiol. R e v . 33, 245 (1953)) in the tielief that adiposity is sdverbcly rclated to health. In- formation on children and adolcsccnts is not ah plentiful.
Some data. on total body water in chil- dren arc available (B. F'riis-Hwnsen, Pedi- atrics 28, 169 (1961 1 1, and also data on body density incasuremcnts ( .J . Parizkova, J . Applied Physiol. 16, 173 (1,961 1 and subcutaneous tissue thickness (Sutrition Revieer>s 20, 5'66 (1962) ; 8. 11. Garn and J . A. Haskell, Science 129, 1615 (1959)) . Estimates of body fat derived froin whole body potashiuni mcasurcments are also in the literature ( C. Forbes, Pediatrics 29,477 (1.962) 1. ,4 i~evien. of physiological and coin- positional changes in adolesccncc has re-
cently been published (F. P. Heald, IZI Daugela, and P. Brunschuyler, New Eng. J M e d . 268, 192 (1963)) .
The authors of the present report gicr data on adolescent boys, upon whom meas urements of total body water, body density and subcutaneous tissue thickness wen inade. Heald et aZ. (Pediatr ics 31, 28 (196S)i studied 66 boys, aged 12 to 11 years, who were members of a boy's swim niing club.
Total body water was measured by deu terium oxide dilution. The isotope was giva intravenously, and the concentration II blood serum deterinined either by inai spectrometry or by the falling drop method Body density was obtained by iindcrwah weighing. Residual lung volume was meiu ured by the helium dilutyon technique. Th accuracy of the total body water deter
- March 196.41 NUTRITION REVIEWS I i ) mination is said to be 400 ml., that of tlie density measurement to be 1.4 per cent.
Fat content was calculated from total body water according to tlie following for- mula: fat = weight - total water/0.718. The densitonietric formula was: fraction fat = (4.0439/density) - 3.6266.
Skinfold thickness a t six sites was ineas- ured with a constant pressure caliper, and subcutaneous adipose tissue by roentgenog- raphy of the chest and arm. I n connection with tlie latter nieasurements the total and lean brachial breadths were converted into areas of cross section of an imaginary cyl- mder, and the lean area subtracted from the total. This yielded the approximate are:^ of adipose tissue in tlie brachiuni, whicli was expressed as :t percentage of total brachial area. This inatliematical device autoniatically increases the absolute (though not tlie relative) differences among aubjects, since d (area 1 must equal 2 d (radius).
The results of this study show a gradual mrease in body specific gravity from age 12 through 17 years. At the younger age, specific gravity of seven subjects averaged 1052; a t the older age the average value for six subjects was 1.081. Although there is a fairly wide scatter in the data, the au- thors have assumed a linear decline in per tent of fat with age, and present an equa- tion for this regreasion as calculated from he specific gravity values. On tlie basis of this equation, 12 year old boys contain an average of 23 per cent fat, and 18 year olds 11 per cent fat.
In analogous fashion, per cent of body rater increases during this same age inter- val, from 61 per cent a t age 12 to 65 per cent at 18 years of age. Thus, fa t content also declines on tlie basis of this ineasure- ment.
Most of tlie skinfoltl ineasureiiieiits reveal asimilar trend in that a decrease in thick- L ~ S occurs with age. For example, the right tnceps skiiifold is 10.2 mm. in 12 year olds, ud 7.7 inm. in 18 year olds. The only ex-
ception to this trend is the scapular area, where a slight increase occurred with age.
Roentgenograinmetric estiniates of sub- cutaneous adipose tissue thickness revealed age changes of somewhat greater magnitude than the caliper iiieasur~inents. The de- crease in tlie triceps area, for inht:mce, was 50 per cent during the sanie period. The au- thors emphasize the fact that this decrease in adiposity is nunierically tlic sa i i i~ as that derived froin ni~asurenients of total adiposity based on dcnsitonirtric data.
This paper includes a discussion of the hydration of the fat-free body, and the changes wliicli occur in this calculated pa- raineter during tlie age range under study. Using total body water values, and fat val- ues as calculated from clensitonietry, the authors calculate that the fat free body of a 12 year old boy contains 79.5 per cent water. This is considerably higher than the 71.8 per cent figure used by many investi- gators based on the reference man. Tlie same calculation for the 18 year old yields a more reasonable figure, namely a 73 per cent water of tlie fat free body inass. At face value, the authors conclude, these data indicate that man is unusual in at- taining niature hydration so late in his growth.
Such a conclusion assullies for hotli tlic total body water and densitoinetric nieth- otls a precision which they may well not pwsess. Moreover, tlie assuiiiption is made that body fat can be estimated from densi- tonietry in 12 year olds by using tlie hame formula for calculation as that used in adult b .
Tlie authors have established that a trend towards decreasing adiposity is evi- dent during adolescent growtli in boys, and that this trend can be appreciated froni a variety of iiieasurcnients : densitoiiietry, total body water, pinch calipers, and soft tissuc roentgenography. They failed to find, in contrast to others (see A-ufrition Re-
pass through an early fat period. Tliic viizzrs 20, 286 (196,) ) that aclolescent boy:.
74 NUTRITION REVIEWS [VOZ. 22, No.!
may possibly reflect tlie type of population onstration of the usefulness of tlie mart sainple selectcd for study, namely swim- simple measurements, such as triceps skin. iiierb. fold, in estiniating relative adiposity 11i
Of great practical iiiiportance is the deiii- this age group.
CHANGES IN PLASMA PROTEINS DURING PREGNANCY
Plxgtiaticy as nccotiapniizcd b y n riutnbct of altciut ioria a t L plasma p i otcwis Furtliei Ltioidetlge of these changes mid t h c w zii ferrclatzonshi~is cati lend to better under- ataidaiig of naetnbolac piocc.\ses chcitncter izirig normcll cittcl pnlhologzr pregrianczes.
Changes in tlie plasina protein fractions and the urinary protein pattern in the course of pregnancy and tlie early post- partum state are of interest both as they reflect nutritional status and as they char- acterize patliologic gestations. Early studies of the serum protein fractions in pregnancy used inoving boundary electrophoresis. E. K. Smith, R. R. de Alvarez, and J. Forsander (Am. J . Obstet. Gynec. 77, 3.96 (1959); iVutrition Revaews 17, 233 (1959)) used paper electrophoresis to study total serum proteins, protein fractions, and lipo- protein distribution in a small series of nor- mal pregnancies.
Tlie decrease in serum albumin, decrease followed by a rise in a-globulin, and increase in p-globulin, reported by them, together with a steady fall in y-globulin, are typical of previous work. It is unfortunate that the values have frequently been presented as percentages of the total protein, whereas absolute values should be more meaningful in distinguishing between real and merely apparent changes.
Several recent papers have added sub- btantially to knowledge of various aspects of the circulating and excreted proteins in normal and pathologic pregnancy. P. Re- boucl, .J. Groulade, P. Groslainbcrt, and 1LI. Colomb (din. J . Obstet. Cynec. 86, 880 (1963) 1 reexamined the influence of preg- nancy and the postpartum state on plasma proteins