Weight for Height

BPK303

Summer 2015

Desirable Body Weight

Desirable, ideal, optimal “What weight should I be?” Weight for height Weight for height with frame size Weight with optimal % body fat BMI - Body Mass Index

Weight for Height

Epidemiologists needed a measure of obesity

Often questionnaire data on height and weight alone

“Ideal” and “Desirable” Weight tables Metropolitan Life Weight for Height Tables

Weight for Height Tables

Metropolitan Insurance Co., 1983, weights at ages 25-59 based on lowest mortality.

Weight in pounds according to frame (in indoor clothing weighing 3 lbs., shoes with 1" heels).

Frame Size

Estimate of Skeletal Proportion

KIN-Scale proportional breadths & widths represent a detailed appraisal of

frame size

Range of Humerus Width (cm) for Medium Frame Size by Height group

Weight for Optimal % Body Fat

If you know the current % body fat, weight for any optimal % body fat can be calculated.

Consensus of an expert panel (1986).

Arbitrary cut-off points.

Calculation of optimal weight range

1. Calculate Fat Weight (FW) FW = body weight x Ft

Where Ft = fractional expression of % body fat

2. Calculate Fat-Free Weight (FFW) FFW = Body Weight – FW

3. Calculate the desired target weight (TW)

TW = FFW / (1 – Fx)

Where Fx = fractional expression of % body fat

Assumes no change in FFM as Body Fat changes

Not recommended since based upon a % Fat with considerable error in individual estimates (SEE = 3.7% Fat)

8

Calculation of optimal weight range

Body Mass Index(Quetelet Index - 1833)

Quetelet (1833)

Tall adults are more linear than short adults. Fully developed individuals: the weight of an

individual at different heights is related to the square of the stature:

[WT] = HT2

During development: the squares of weight were related to the fifth powers of height:

[WT]2 = HT5 → [WT] = HT2.5

10

Canada Fitness Survey (1981)

(20-29 years old)

WT/HT BMI WT/HT3 WT/HTb

Females b=1.549

Weight 0.967 0.861 0.706 0.918

Height 0.144 -0.127 -0.369 -0.005

S 5 SF 0.805 0.821 0.781 0.821

Correlational Analysis of Weight (WT) and Height (HT) indices in a sample of SFU Kin 303 students (aged 18–25 years)

12

Males (b=1.660) WT/HT BMI WT/HT3 WT/HT1.66 HT Height .22 -.13 -.44 -.01 -- Weight .95 .78 .55 .85 .51 Sum of 6 Skifolds .52 .57 .56 .56 -.11 Skinfold-adjusted Arm Girth relaxed .72 .67 .56 .70 .14 Skinfold-adjusted Calf Girth .54 .44 .30 .48 .29 Humerus (elbow) Width .47 .28 .07 .35 .55 Femur (knee) Width .56 .41 .23 .47 .46

Females (b = 1.906) WT/HT BMI WT/HT3 WT/HT1.906 HT Height .38 -.04 -.50 .00 -- Weight .95 .72 .37 .75 .66 Sum of 6 Skifolds .49 .49 .40 .49 .10 Skinfold-adjusted Arm Girth relaxed .436 .40 .30 .40 .13 Skinfold-adjusted Calf Girth .43 .35 .21 .36 .24 Humerus (elbow) Width .50 .29 .02 .31 .56 Femur (knee) Width .66 .46 .19 .49 .54

Ward R, Anderson G. 2012 (unpublished)

Sum of 6 Skinfolds vs BMIKIN-Scale Males and Females

13

Ross et al. 1988

Correlations of BMI are “good” with sum of skinfold corrected-girths and even bone widths

Correlations of BMI with sums of selected anthropometric measures (Canada Fitness Survey 1981)

Sum of 5 Skinfolds

Sum of corrected Limb Girths

Sum of Bone Breadths

Males 0.67 0.56 0.36

Females 0.72 0.48 0.42

Correlational Analysis of Weight (WT) and Height (HT) indices in a sample of SFU Kin 303 students (aged 18–25 years)

15

Males (b=1.660) WT/HT BMI WT/HT3 WT/HT1.66 HT Height .22 -.13 -.44 -.01 -- Weight .95 .78 .55 .85 .51 Sum of 6 Skifolds .52 .57 .56 .56 -.11 Skinfold-adjusted Arm Girth relaxed .72 .67 .56 .70 .14 Skinfold-adjusted Calf Girth .54 .44 .30 .48 .29 Humerus (elbow) Width .47 .28 .07 .35 .55 Femur (knee) Width .56 .41 .23 .47 .46

Females (b = 1.906) WT/HT BMI WT/HT3 WT/HT1.906 HT Height .38 -.04 -.50 .00 -- Weight .95 .72 .37 .75 .66 Sum of 6 Skifolds .49 .49 .40 .49 .10 Skinfold-adjusted Arm Girth relaxed .436 .40 .30 .40 .13 Skinfold-adjusted Calf Girth .43 .35 .21 .36 .24 Humerus (elbow) Width .50 .29 .02 .31 .56 Femur (knee) Width .66 .46 .19 .49 .54

Ward R, Anderson G. 2012 (unpublished)

16

Table 5-5: Correlations of Body Mass Index with Height, Weight Sum of Six Skinfolds (S6SF), Sum of Four Skinfold-adjusted Girths (SumMuscle) and Sum of Humerus and Femur Widths (SumBone) in KIN-Scale data.

BMI Height Weight S6SF SumMuscle SumBone

Male n = 230 0.040 0.852** 0.698** 0.328** 0.353**

Female n = 336

0.048 0.852** 0.689** 0.372** 0.518**

Percentage body fat as measured by dual-energy X-ray absorptiometry (DXA %fat) versus BMI and 1/BMI in women from 3 study sites combined. Reproduced from Gallagher (2000)

17

Percentage body fat by dual-energy

X-ray absorptiometry

(DXA %fat) versus 1/BMI

by sex for each of the study sites.

Reproduced from Gallagher (2000)

18

Predicted percentage body fat by sex and ethnicity

based on 4-C percentage body fat

19

Women Men

Age and BMI African American Asian White African

American Asian White

% % % % % %

20–39 y BMI < 18.5 20 25 21 8 13 8 BMI ≥25 32 35 33 20 23 21 BMI ≥30 38 40 39 26 28 26 40–59 y

BMI < 18.5 21 25 23 9 13 11 BMI ≥25 34 36 35 22 24 23 BMI ≥30 39 41 41 27 29 29 60–79 y

BMI < 18.5 23 26 25 11 14 13 BMI ≥25 35 36 38 23 24 25 BMI ≥30 41 41 43 29 29 31

Children & Youth

20

During development: the squares of weight were related to the fifth powers of height:

[WT]2 = HT5 → [WT] = HT2.5

B-values of height predicting weight in yearly age groups for Canada Fitness Survey (CFS) and Coquitlam Growth Study (COGRO) boys and girls

21

1

1.5

2

2.5

3

3.5

7 8 9 10 11 12 13 14 15 16 17 18

Age Group (years)

b-v

alu

e

CFS Boys

CFS Girls

COGRO Boys

COGRO Girls

22

All Boys CFS (ages 7 – 18 yrs) N=2438 WT/HT BMI WT/HT3

Height .880* .663* -.178* Weight .988* .873* .160* Sum of 5 Skinfolds .467* .629* .643* Skinfold-adjusted relaxed Arm Girth .907* .812* .174* Skinfold-adjusted Calf Girth .840* .713* .052* Humerus (elbow) Width .874* .723* -.009 Femur (knee) Width .861* .738* .054*

All Girls CFS (ages 7 – 18 yrs) N=2269 WT/HT BMI WT/HT3

Height .804* .553* -.093* Weight .984* .863* .354* Sum of 5 Skinfolds .710* .796* .684* Skinfold-adjusted relaxed Arm Girth .839* .767* .375* Skinfold-adjusted Calf Girth .596* .506* .171* Humerus (elbow) Width .765* .612* .122* Femur (knee) Width .816* .701* .250*

* Correlation is significant at the 0.05 level (2-tailed).

CDC BMI Growth Charts

23

BMI

BMI is not an indicator of body fat in individuals it is a measure of weight for height

It can be useful as a population screening and awareness device, but not in individual prescription

May be useful used in conjunction with other measures