7/27/2019 Am J Clin Nutr-1986-Garn-996-7

1/2

Editor ia l

99 6 Am J C lin M ar l9 86 ;44 :99 6-7 . P rin ted in U SA . 1986 Am erican Soc ie ty fo r C lin ica l N u trition

Th ree lim ita tion s o f the body m ass index1S tan ley M G arn , P /iD , W illiam R Leonard , M A , an d V ic to r M H aw th orn e, M D

Al though th e w t/h t2 o r B ody M ass Index(BM I) h as a tta in ed g row ing popu lar ity in thepas t fe w yea rs (1), th e tw o com ponen ts of th isin dex an d the ir rela tiv e w e igh ting suggest pos -s ib le l im ita tion s on its u se . S in ce s ta tu re (ie ,s tand in g h eigh t) is one com ponen t, th e BM Im ay be sta tu re dependen t over at lea s t p art ofth e ag e ran ge . A ga in , th e u se o f sta tu re as ad iv iso r sug ge s ts tha t th e BM I m ay a lso b e a!-fected by re la tive le g len gth or rela tiv e s ittin gh eigh t. F in a lly , th e u se of w e igh t as th e n u -m erato r suggests that th e BM I-lik e w e igh ti tse lf-may refle c t b oth lean tissu e and fat tis -su e to a com parab le degree .

I f w e turn fi rs t to th e exten siv e data o f th efir st N ationa l H ea lth an d N utr ition E xam i-n ation Su rv ey (NHANES I) , readily avai lab leon tape an d famil iar to m o st re ade rs of thisjou rna l (2 ), th e BM I is ind eed sta tu re d epen -den t b u t in d ifferen t d irection s a t d ifferen tpo in t s in th e l ife cy cle . For NHANE S I , co r-re la t ions b etw een s ta tu re an d th e BM I ap -prox imate 0 .30 for ch ild ren , shift dur ing ad -o le s cence , and b ecom e negative in adu lt yea rs(T ab le 1 ). T h e m ass ive da ta o f th e N ationa lC ollab o ra tiv e P e rina ta l P ro je ct (N C PP ) co n -firm th ese t re nd s; c or re la ti on s be tw een s ta tu rean d the BM I aga in app rox im a te 0 .3 0 fo r ch il-d ren bu t ave rag e -0 . 1 2 fo r 40 0 00 3rd and4th decade w om en . T hus th e assum p tion tha tth e BM I is in depen den t ofsta tu re is no t qu itet rue fo r ad u lts and especia l ly no t t rue fo r c hil-dren .

A n th ro pom e tric d ata in c lu ded in NHANE SI a lso rev ea l th e ex ten t to wh ich BM I re flec tsbody propor t ion s o r m ore specifically s i t t inghe igh t rela tive to stand ing h eigh t (T ab le 2 ). A ta ll ag es con s ide red (age s 5 -50 ) the co rre la tio nb e tw een BM I a nd r ela tiv e si tting h eig h t (si ttinghe ig h t/s ta tu re) is a t lea s t 0 .15 and gene ra llyexceeds 0 .20 . W ith n = 596 for ado le scen t

m ale s to n = 3858 fo r y ou ng adu lt w om en , a llo fth ese va lu es o f r ar e statistically s ignificant .H ow ever, th e po in t in q uestion is th e m agn i-tu des o f th e corre la tion s an d th eir im p lica -tion s . C h ild ren , ad o le scen ts , or adu lts w ithsho rt legs fo r th e ir he igh t have h igher BM Ivalu es , w h ich ind ica tes th e ex ten t to w h ichBM I is a lso a m easu re o f body bu ild o r bodyproport ions.

Whe n th e BM I is fu rth er exp lored in rela -tion to fram e size , L ean B ody M ass , and fat-nes s , aga in on an age -sp ec ific b asis , it is seento rela te to a ll th ree. W ith u se o f data fromth e T ecum seh (M ich igan ) C omm unity H ea lthSurvey to in c lude the rad iog ram metr ica lly -d e te rm ined bony chest b read th (3 ) a s in T ab le3, th e correla tion s approx im ate 0. 5 overal l .F or the s ame subjec ts a r ranged b y ag e in ter -v a ls , c or re la ti on s wi th th e tr ic eps sk in fo ld ap -prox imate 0 .7 , as sh ow n in th e tab le . If w efu r the r e s t imate L ean B ody M ass b y su b tr ac t-in g e s t ima ted fa t w eigh t from to ta l body w eigh t(4 ), co rre la tion s w ith BM I then approx im a te0 .65 fo r m ales aged 30 -50 . A cco rd ing ly , it isclea r tha t BM I refle c ts bo th the w e igh t o f le antissu e an d the w e igh t offa t tis su e and fo r som eag e g roup s, a t least, it m ay be a be tter m easureof am oun t oflean than of rela tive fa tn ess .

Unde r th es e c ir cu m sta nc es and w ith sam -p ie s o f co nsid er ab le s ize (up to and ex ceed ing40 000 ), it is c le ar th at th e BM I is n o t qu iteindepend en t ofsta tu re , especia l ly a t th e youn -ger ag es . M oreov er, th e BM I is in flu enced by

I From th e C en te r fo r H um an G row th and D eve lop -m en t, The U n ive rsity o f M ich ig an , 300 No rth Ing allsB u ild in g , A nn Arbor , M I and the D epa rtm en t o f E p ide -m iolog y , Schoo l o f Pub lic H ea lth , The Un ivers ity ofMich igan , A nn A rbo r, M I.

Rece ived May 5, 1986 .Accep ted for pub lica tion Ju ly 1 , 1986.

7/27/2019 Am J Clin Nutr-1986-Garn-996-7

2/2

ED ITOR IAL 997

* S i tt in g h e ig h t /s t a tu re .

TABLE 1R elationship betw een stature and BM I in NHANES 1

A G r o u pM

,i r n

F e m r

5-10 1112 0.32 1165 0.2711-15 897 0.24 895 0.1716-19 596 0.04 614 -0.0820-35 1 7 0 6 -0.02 3766 -0.0836-50 1 4 8 5 -0 .0 5 2 5 1 3 -0.08

S Ag e corrected v al ues of r.

body propo rtions (r ela tive leg leng th or rela tiv esitting h eigh t) su ch that shor ter -legged mdi -viduals have BM I values higher b y as m ucha s 5 un its . F ina lly , BM I (like w eigh t) is in flu -enced nearly to an eq ual degree by both th elean and th e fa t com par tm en ts o f th e hum anbody. It is a s m uch a measure of L ean BodyM ass as it is a measure of fa tn ess or obesity.

Whi l e these comment s apply specifically toth e B M I ca lcu la ted a s w eigh t (kg ) did b ystature (m2), they also app ly to th e h t/V w t ratioand sim ila r in d ices tha t express w e igh t fo rhe igh t. T hu s, fam ily -l in e resemblances inB M I, w h ich approx im a te 0 .2 0-0 .25 for pa r-en ts an d sub adu lt ch ild ren , m ay re flec t s im i-larities in body build and proportions and inlean or fa t-free mass as m uch a s fam ilia l re -semblances in fatness. Similarly, resemblancesin B M I between o lder parents and their adultchildren m ay or m ay no t rev ea l w he ther fa t-ness is biologically inherited. Relative leglength, frame size, and am oun t of l ean ti ssueTABLE 2E f f e c t o f rela t iv e s it t i n g h e i g h t o n B M I in N H A N E S I

Males FemalesAgeGmup n r , r

5-101 1 - 1 516-192 0 - 3 53 6 - 5 0

11128 9 859 6

1 7 4 31483

0.190 .230.190 . 2 10.21

11668 9 5614

3 8 5 82527

0.190 . 2 50.260.170.15

TABLE 3Relationship between bony chest breadth and BM I andsubcutaneous fat and BM I

B on y c he stbesadth T ri skinfod

Age ii r n r

Males 5-10 310 0.51 685 0.601 1 -1 5 3 7 3 0 .6 5 5 3 3 0 .7 216-18 173 0 . 5 3 25 3 0 . 7 220-30 1 4 1 0 .4 8 2 4 9 0 .6 830-40 81 0 .57 1 4 5 0 .6 74 0 - 5 0 61 0.51 116 0.565 0 - 6 0 22 0.67 40 0.71

Females 5 - 1 0 33 1 0 . 5 2 7 0 9 0 .6 01 1 - 1 5 343 0.63 502 0 . 8 116-18 153 0.55 247 0.7420-30 132 0.56 218 0 . 8 030-40 92 0 .4 1 1 4 7 0 .7 34 0 -S O 7 3 0 .5 1 1 0 8 0 .7 850-60 2 1 0 .37 4 3 0 .76

S A ge c o rre c te d v alu es o f r. All d a t a fro m Te c um s ch ,M ichigan Community H ealth Survey examination round2 .

are also involved, and o lder parents m ay re-semble their adul t children in these respectsaswe l l (5 ) .

References

1. K eys A , Fidanza F, K arvonen M J, K imura N , TaylorHL I ndices ofrelative w eight and obesity. J ChronicDis l9 7225 :3 29 -43 .2 . L a n d is J R , Lepkowski JM , Ekiund SA, S tehouwerS A . A s ta tis t ic a l methodology fo ra na lyz in g da ta fro ma c o m p le x survey: t he f ir st nat iona l health a n d n utri-t io n e x a m in a t io n s u rv e y . H y a t t s v ille , M D: D ep ar t-ment ofHeal th and H um an S erv ices , 19 82 . [D HH Spublication n o ( PH S) 8 2- 23 66 .]3 . Garn S M , P esic k S D, H aw thorne V M . T he b on y ch estbreadth as a frame size standard in nutritional as-sessment. A m J Clin Nutr l983 ;37 :3 l5-8 .4. Garn SM , L aV elle M . Family- line origins ofthe low-fa t and lo w -le an c h ild o r a do le sc e nt. In : C o he n S A ,e d . T he u nd e rw e ig h t infant, child and adolescent EastN o r w a lk : A p p le t o n .C e n t u ry - C ro f ts , ! 9 8 5 : 1 5 - 2 9 .

5 . Stunkard A J, S#{ 248} rensenA , H ani s C , et al . A n adoptionstudy ofhuman obesity. N Engi J Med 1 98 6, 31 4: 19 3- 8.