24 Introduction to Human Nutrition
skinfold thicknesses can be diffi cult. This can be over-
come by measuring only the skinfold thickness at the
upper arm, for example the triceps. However, the
error can be large because the triceps does not neces-
sarily represent the total amount of subcutaneous fat.
With advancing age, the triceps skinfold becomes less
representative of total body fat.
In elderly subjects, the correlation between skin-
fold thickness and total body fat as measured by
densitometry is generally lower than in young and
middle-aged adults. This is due to an increased
amount of internal fat in the elderly. Obese subjects
are diffi cult to measure and the error is large even
when measured by trained observers. This is also the
case in subjects with edema, in whom the thickness
of the subcutaneous adipose tissue is easily overesti-
mated. In patients with human immunodefi ciency
virus (HIV) lipodystrophy, peripheral subcutaneous
fat may be almost absent, while abdominal fat is
increased. In this situation, skinfolds can be very mis-
leading as indicators of total body fat, and should be
used only to assess regional fat.
The calculation of the body fat percentage once the
skinfolds have been measured is very simple. For a
given skinfold thickness, the amount of body fat can
be read from a table (Table 2.6).
The prediction error in body fat percentage is 3–
5% compared with densitometry, depending on age,
gender, and level of body fatness. Given the possible
error in densitometry (3%), this means that in extreme
cases body fat from skinfolds can be as much as 10–
15% off.Other anthropometric variables
Measurements of widths of skeletal diameters provide
an indication of the amount of skeletal mass. There
are formulae that allow the calculation of the skeletal
mass from body height, wrist diameter, and knee
diameter. The current reference data for ideal weight
in the USA use the elbow diameter to classify people
into three types of body build.
In elderly subjects, the measurement of stature can
be diffi cult owing to kyphosis and/or shrinkage of the
spinal vertebrae. Knee height can then be used to
predict the maximal stature during lifetime. Arm
span is also used for that purpose. However, one has
to realize that the current prediction formulae are
developed in younger populations, in which the rela-
tionship between stature and surrogate measure-
ments may be different. In addition, the prediction
error (3–5 cm) is relatively high. Knee height can also
be used by itself (without predicting total stature),
when comparing stature-adjusted body composition
between young and old people.
Circumferences of the extremities or the trunk are
used to obtain information on body composition.Table 2.6 Body fat percentage from the sum of four skinfolds (biceps, triceps, subscapular, suprailiac) in males and females of different agesa
Skinfolds (mm)
Age (Males) Age (Females)
17–29 30–39 40–49 ≥ 50 60–87 17–29 30–39 40–49 ≥ 50 60–8720 8 12 12 13 24 14 17 20 22 34
30 13 16 18 19 27 20 22 25 27 37
40 16 19 21 23 29 23 26 28 30 39
50 19 22 25 27 31 27 28 31 33 41
60 21 24 27 29 32 29 31 33 36 42
70 23 25 29 32 33 31 33 35 38 43
80 25 27 31 34 34 33 34 37 40 44
90 26 28 33 36 35 35 36 38 41 45
100 28 29 34 37 36 36 37 40 43 46
110 29 30 36 39 37 38 39 41 44 47
120 30 31 37 40 37 39 40 42 45 48
130 31 32 38 42 38 40 41 43 46 48
140 32 33 39 43 38 41 42 44 47 49
150 33 34 40 44 39 42 43 45 48 49
a Based on data from Durnin and Womersley (1974) for the age groups 17 to ≥50 and on Visser et al. (1994) for the elderly.