The body density of young to middle aged women can be estimated from body measurements using the generalized equations developed by Jackson, Pollock and Ward.

Problems with regression equations:

(1) regression equations are linear while the relationship between skinfold fat and body density are curvilinear

(2) age affects body density

(3) need 200 or more subjects for better representation

Subjects studied:

(1) 331 women from 18 to 55 years of age

(2) 249 women were used for the validation sample and 82 subjects were used for cross-validation.

Measurements:

(1) Skinfold thicknesses were measured in mm using a Lange skinfold fat caliper.

(2) Gluteal circumference was measured in centimeters using a Lufkin steel tape.

Sites of skinfold thickness measurement:

(1) chest

(2) axilla

(3) triceps

(4) subscapula

(5) abdomen

(6) suprailium

(7) thigh

sum of 7 skinfolds =

= SUM(skinfold thickness from all 7 sites in mm)

sum of 4 skinfolds =

= (skinfold thickness triceps in mm) + (skinfold thickness abdomen in mm) + (skinfold thickness suprailium in mm)+ (skinfold thickness thigh in mm)

sum of 3 skinfolds =

= (skinfold thickness triceps in mm) + (skinfold thickness thigh in mm) + (skinfold thickness suprailium in mm)

Sum of 7 Sites

Equation 1 (R = 0.852, standard error 0.0083)

body density in g per mL =

= 1.0970 - (0.00046971 * (sum of 7 skinfolds in mm)) + (0.00000056 * ((sum of 7 skinfolds in mm)^2)) - (0.00012828 * (age in years))

Equation 2 (R = 0.850, standard error 0.0084)

body density in g per mL =

= 1.23173 - (0.03841 * (LN(sum of 7 skinfolds in mm))) - (0.00015 * (age in years))

Equation 3 (R = 0.865, standard error 0.0080)

body density in g per mL =

= 1.1470 - (0.00042359 * (sum of 7 skinfolds in mm)) + (0.00000061 * ((sum of 7 skinfolds in mm)^2)) - (0.0006520 * (gluteal circumference in cm))

Equation 4 (R = 0.864, standard error 0.0080)

body density in g per mL =

= 1.25475 - (0.03100 * (LN(sum of 7 skinfolds in mm))) - (0.00068 * (gluteal circumference in cm))

Equation 5 (R = 0.867, standard error 0.0079)

body density in g per mL =

= 1.1470 - (0.00042930 * (sum of 7 skinfolds in mm)) + (0.00000065 * ((sum of 7 skinfolds in mm)^2)) - (0.00009975 * (age in years)) - (0.00062415 * (gluteal circumference in cm))

Equation 6 (R = 0.867, standard error 0.0079)

body density in g per mL =

= 1.25186 - (0.03048 * (LN(sum of 7 skinfolds in mm))) - (0.00011 * (age in years)) - (0.00064 * (gluteal circumference in cm))

Sum of 4 Sites

Equation 7 (R = 0.849, standard error 0.0084)

body density in g per mL =

= 1.0960950 - (0.0006952 * (sum of 4 skinfolds in mm)) + (0.0000011 * ((sum of 4 skinfolds in mm)^2)) - (0.0000714 * (age in years))

Equation 8 (R = 0.845, standard error 0.0085)

body density in g per mL =

= 1.21993 - (0.03936 * (LN(sum of 4 skinfolds in mm))) - (0.00011 * (age in years))

Equation 9 (R = 0.861, standard error 0.0081)

body density in g per mL =

= 1.1443913 - (0.0006523 * (sum of 4 skinfolds in mm)) + (0.0000014 * ((sum of 4 skinfolds in mm)^2)) - (0.0006053 * (gluteal circumference in cm))

Equation 10 (R = 0.859, standard error 0.0081)

body density in g per mL =

= 1.24374 - (0.03162 * (LN(sum of 4 skinfolds in mm))) - (0.00066 * (gluteal circumference in cm))

Equation 11 (R = 0.862, standard error 0.0081)

body density in g per mL =

= 1.1454464 - (0.0006558 * (sum of 4 skinfolds in mm)) + (0.0000015 * ((sum of 4 skinfolds in mm)^2)) - (0.0000604 * (age in years)) - (0.0005981 * (gluteal circumference in cm))

Equation 12 (R = 0.861, standard error 0.0081)

body density in g per mL =

= 1.241721 - (0.031069 * (LN(sum of 4 skinfolds in mm))) - (0.000077 * (age in years)) - (0.000635 * (gluteal circumference in cm))

Sum of 3 Sites

Equation 13 (R = 0.842, standard error 0.0086)

body density in g per mL =

= 1.0994921 - (0.0009929 * (sum of 3 skinfolds in mm)) + (0.0000023 * ((sum of 3 skinfolds in mm)^2)) - (0.0001392 * (age in years))

Equation 14 (R = 0.838, standard error 0.0087)

body density in g per mL =

= 1.21389 - (0.04057 * (LN(sum of 3 skinfolds in mm))) - (0.00016 * (age in years))

Equation 15 (R = 0.851, standard error 0.0084)

body density in g per mL =

= 1.1466399 - (0.000930 * (sum of 3 skinfolds in mm)) + (0.0000028 * ((sum of 3 skinfolds in mm)^2)) - (0.0006171 * (gluteal circumference in cm))

Equation 16 (R = 0.849, standard error 0.0084)

body density in g per mL =

= 1.23824 - (0.03248 * (LN(sum of 3 skinfolds in mm))) - (0.00067 * (gluteal circumference in cm))

Equation 17 (R = 0.854, standard error 0.0083)

body density in g per mL =

= 1.1470292 - (0.0009376 * (sum of 3 skinfolds in mm)) + (0.0000030 * ((sum of 3 skinfolds in mm)^2)) - (0.0001156 * (age in years)) - (0.0005839 * (gluteal circumference in cm))

Equation 18 (R = 0.853, standard error 0.0083)

body density in g per mL =

= 1.23530 - (0.03192 * (LN(sum of 3 skinfolds in mm))) - (0.00013 * (age in years)) - (0.00062 * (gluteal circumference in cm))

Note - The following equations are similar in components:

• 1, 7 and 13

• 2, 8 and 14

• 3, 9 and 15

• 4, 10 and 16

• 5, 11 and 17

• 6, 12 and 18

Siri Equation

percent body fat =

= (((4.95 / (body density in grams per cubic cm)) - 4.5) * 100