How To Measure Skin Folds Without Calipers
The skinfold method, the measurement of subcutaneous fat folds, is the most widely adopted field method for the assessment of body fat, particularly in children.
It is based on the principle that fatty is of a known density and by "summing" measurements of subcutaneous fatty thickness across the body, total and regional fat can be estimated.
Skinfold thickness measurements are typically used to rank individuals in terms of relative full "fatness", or to assess subcutaneous fat at various regions of the trunk.
Population specific equations are used to derive estimates of percent body fat.
In infancy, it might be the sole tool available for assessing body composition longitudinally as other methods may not be feasible, or may only be suitable for use at body sizes due east.g. PEA POD, tin can only measure out infants upwards to 10kg.
The skinfold method involves measuring the skinfold (subcutaneous fat) thickness at specific sites of the trunk using a skinfold caliper and a non-stretchable measuring record to correctly locate the measurement area.
Equipment
Caliper
The cost of calipers ranges from £9 to approximately £300. For research purposes, calipers with a more refined scale (e.m. 0.i mm intervals) and constant pressure of 10g/cm3 between the jaws are desirable. Examples include the Holtain (see Effigy i), Lange and Harpenden calipers (see instrument library for more details). The Lange and Harpenden calipers have been used in developing prediction equations and reference values (Lee 1996). The Lange is most pop in the The states, and the Harpenden and Holtain in Europe.
Figure 1 Example of skinfold caliper typically used in children and infants.
Source: https://holtain.co.britain/tw.php
Measuring tape
Typically a non-stretch fibreglass or plastic measuring tape – such every bit those used in measurement of height – is used to locate the anatomical midpoints on the body where the skinfold measurement is taken.
Protocol
Skinfold measurement can be obtained from 2 to 9 different standard anatomical sites around the body using a caliper, every bit shown in Figure 2. The subscapular and triceps skinfolds are the most unremarkably used.
Figure 2 Anatomical sites for skinfold thickness measurement taken at the left side.
Source: MRC Epidemiology Unit.
The following are the nine anatomical sites (equally illustrated in Effigy 2) that are well-nigh commonly used in the cess of skinfold thickness:
- Chest or pectoral skinfold: For men, go a diagonal fold half manner between the armpit and the nipple. In women, a diagonal fold 1/3 of the way from the arm pit to the nipple.
- Mid-Axillary: A vertical fold on the mid-axillary line which runs direct down from the eye of the armpit.
- Supra-iliac or flank: A diagonal fold just to a higher place the front frontward protrusion of the hip bone (only above the iliac crest at the midaxillary line).
- Intestinal: A horizontal fold about 3 cm to the side of the midpoint of the omphalos and 1 cm below it.
- Quadriceps or mid-thigh: A vertical fold midway between the knee and top of the thigh (between the inguinal pucker and the proximal border of the patella).
- Triceps: A vertical fold midway betwixt the acromion process and the olecranon procedure (elbow).
- Biceps: A vertical pinch mid-biceps at the same level the triceps skinfold was taken.
- Subscapular: A diagonal fold just beneath the junior angle of the scapula.
- Medial Dogie: The foot is placed flat on an elevated surface with the knee joint flexed at a ninety° angle. A vertical fold taken at the widest betoken of the calf at the medial (inner) aspect of the calf.
- It is standard to take measurements to the right side in the The states, to the left side in Europe. When selecting the side it is important to be consistent.
- The site to be measured is marked in one case identified.
- A non-stretchable record like in Effigy two can be used to locate anatomical midpoints on the torso.
- The skinfold should be firmly grasped by the thumb and alphabetize finger of the left manus well-nigh 1 cm proximal to the skinfold site and pulled away from the trunk (run into Effigy three).
- The caliper is in the right hand (perpendicular to the axis of the skinfold and with dial facing up).
- The caliper tip should be 1 cm distal from the fingers holding the skinfold.
- The dial is read approx. 4 seconds afterwards the pressure from the measurer's hand has been released on the lever arm of the caliper.
- Measurement is recorded to the nearest 0.2 mm.
- Three measurements are recorded and if consecutive measurements differ past one mm, the measurement is to exist repeated; separated by 15 seconds.
- The technician should maintain force per unit area with the fingers throughout each measurement.
- Measurements should not be taken after exercise as overheat causes a shift in body fluids to the peel and will inflate the skinfold size.
- As hydration level can influence measurements, information technology is recommended to carry out the measurements in a hydrated land.
Figure 3 Quadriceps skinfold thickness in an infant to the left and triceps skinfold thickness in an adult to the right.
Source: MRC Epidemiology Unit.
An instance of a calibration cake with known thicknesses Figure 4 is used to calibrate skinfold calipers. Typically, calibrations are carried out on a monthly basis.
Effigy 4 An example of a scale block.
Source: MRC Epidemiology Unit.
Skinfold thickness are typically recorded in mm. Some calipers record in both mm and cm. The skinfold thickness values should be quality checked during data processing in the same manner as other health related variables, for example by checking for outliers and data entry errors.
Raw skinfold thickness values are oftentimes used and they human action as reliable indicators of regional fatness. In a similar way to trunk mass index (BMI), they can exist converted into standard difference scores (SDS) for longitudinal evaluations.
The triceps site is the most commonly used single-site skinfold measurement equally it is easy to measure out and reference data (east.chiliad. WHO triceps skinfold thickness for historic period) are available for comparison. However, no equations are available for estimating body fatty from a single-site skinfold measurement. Triceps measurement is also used to derive indices of body composition using arm anthropometry.
To convert raw skinfold thickness values into a percent of trunk fatty, population-specific or generalised equations are used. These equations are derived from empirical relationships between skinfold thickness and body density. Many equations firstly calculate body density and crave an additional calculation to guess percent body fat. The Brozek et al (1963) and the Siri (1961) equations tin can be used for this step:
- Brozek: % trunk fat = (457-trunk density) - 414
- Siri = % trunk fatty = (495/body density) - 450
Trunk fat values should be generated from published equations which closely friction match the study population. It is critical that the equation selected for estimating body fat is appropriate to the demographics of the cohort nether investigation (east.g. race, age, and gender).
Several equations are bachelor. The most normally used equations are listed below:
Adults
Jackson & Pollock (1985)
- Men four-Site Skinfold Equation (for calculating % body fat)
% Body Fat = (0.29288 * sum of skinfolds) – (0.0005 * square of the sum of skinfolds) + (0.15845 * historic period) – 5.76377, where the skinfold sites (mm) are abdominal, triceps, thigh and supra-iliac
- Women 4-Site Skinfold Equation (for computing % trunk fat)
% Torso Fat = (0.29669 * sum of skinfolds) – (0.00043 * square of the sum of skinfolds) + (0.02963 * age) + 1.4072, where the skinfold sites (mm) are abdominal, triceps, thigh and supra-iliac
- Women 3-Site Skinfold Equation
% Body Fat = (0.41563* sum of skinfolds) – (0.00112* square of the sum of skinfolds) + (0.03661 * age) + iv.03653, where the skinfold sites (mm) are abdominal, triceps and supra-iliac
Durnin & Womersley (1974)
Durnin & Womersley (1974) developed general equation developed from a heterogeneous group of varying ages. The calculation of trunk fat % involves measuring 4 skinfold sites, triceps, biceps, subscapular and supra-iliac, and substituting the log of their sum into one of the following equations (Tabular array ane), depending on the participant's age and sex activity. The density value can and so exist converted to percentage body fat (%BF) using Siri 1961 or Brozek 1963 equations described above.
Table one Durnin & Womersley equations for the estimation of body density using 4 skinfold sites.
| Historic period (years) | | |
|---|---|---|
| < 17 | | |
| 17-19 | | |
| xx-29 | | |
| 30-39 | | |
| 40 -49 | | |
| > 50 | | |
D = predicted density of the body (g/ml), and L = log of the total of the four skinfolds (mm).
Source: Durnin et al 1974.
Estimates derived using these equations have been compared to those from the criterion 4-component model (see Figures 5 and half-dozen). The Durnin and Wormersley (1974) equation showed significant mean difference/bias of - 2%, while the Jackson and Pollock (1985) equation showed mean bias of -6.6%. Both equations tend to underestimate trunk fat peculiarly in larger individuals. Like results have also been observed in men (Peterson et al., 2003).
Figure five Bland-Altman plot showing the limits of agreement between percentage body fatty calculated with the 4-compartment-model equation (%BF4C; the reference equation) and percentage body fatty calculated with the Durnin and Wormersley equation (%BFDW) in women.
Source: Peterson et al. (2003).
Figure 6 Bland-Altman plot showing the limits of understanding betwixt percentage torso fat calculated with the iv-compartment-model equation (%BF4C; the reference equation) and pct trunk fat calculated with the Jackson and Pollock equation (%BFJP) in women.
Source: Peterson et al. (2003).
Children and immature adolescents
A priori, age- and sex-dependent regression equations published by Weststrate and Deurenberg (1989) that were derived from modification of the Siri (1961) equation (% fat = 495/density-450), are the most suitable for the estimation of % FM in children and adolescents:
- Girls: Fat (%) = [553−vii.3 (Age − 10)] / D − [514−8 (Historic period −10)]
- Boys: Fat (%) = [562−4.two (Age − ii)] / D − [525−4.seven (Age −two)]
Notwithstanding, Slaughter et al. (1988) equations proposed for pre-pubertal, pubertal and post-pubertal males and females are the most commonly used.
Tabular array 2 lists equations used to make up one's mind body limerick values in children and adolescents using skinfold measurement.
Tabular array ii Published equations used to approximate body fatty in children and adolescents from skinfolds.
| Author(s) | Population | Equation(due south) |
|---|---|---|
| Lohman et al. (1984) | Prepubescent children | M and F: Fat (%)=530/D − 489 |
| Lohman et al. (1984) | Prepubescent children | M and F: Fatty (%)=530/D − 489 |
| Weststrate and Deurenberg (1989) | x−18 y (modification of Siri equation) | F: Fat (%)=[553−vii.iii (Age − 10)] / D − [514−8 (Historic period −10)] M: Fat (%)=[562−4.2 (Age − two)] / D − [525−4.7 (Historic period −ii)] |
| Brook (1971) | 1−xi y (predicted from equations for adolescents) | F:D=1.2063−0.0999 (LOG sum of 4 skinfolds) M:D=i.1690−0.0788 (LOG sum of 4 skinfolds) |
| Durnin and Rahaman (1967); Durnin and Womersley (1974) | 13−fifteen.9 y 16−19.ix y | F (13−15.9 y):D=1.1369−0.0598 (LOG sum of 4 skinfolds) M (thirteen−15.9 y):D=1.1533−0.0643 (LOG sum of 4 skinfolds) F (xvi−nineteen.ix y):D=1.1549−0.0678 (LOG sum of iv skinfolds) M (16−19.9 y):D=1.162−0.063 (LOG sum of iv skinfolds) |
| Johnston et al. (1988) | 8−fourteen y | F:D=1.144−0.06 (LOG sum of iv skinfolds) K:D=1.166−0.07 (LOG sum of 4 skinfolds) |
| Deurenberg et al. (1990) | Pubertal F: 13.1 ± 0.15 y Pubertal One thousand: 13.viii ± 0.21 y Post-pubertal F: sixteen.8 ± 0.36 y Post-pubertal F: 17.5 ± 0.39 y | F pubertal:D=1.1074−0.0504 (LOG sum of four skinfolds) + 1.half-dozen (age 10-iii) M pubertal:D=ane.0555−0.0352 (LOG sum of iv skinfolds) + 3.8 (historic period ten-iii) F post-pubertal:D=1.183−0.0813 (LOG sum of iv skinfolds) Thousand post-pubertal:D=1.1324−0.0429 (LOG sum of 4 skinfolds) |
| Sarría et al. (1998) | xi−16.9 y | M (11−13.9): D=1.1516−0.0658 (LOG sum of 4 skinfolds) 1000 (xiv−sixteen.9): D=1.169−0.0693 (LOG sum of four skinfolds) |
| Sloan et al. (1962) | Young women | F: D=one.0764−0.00081 suprai − 0.00088 tric |
| Wilmore and Behnke (1970) | Young women | F: D=1.06234−0.00068 subsc − 0.00039 tric − 0.00025 thigh |
| Slaughter et al. (1988) | Prepubertal F: ten.0 ± i.0 y Prepubertal One thousand: 9.viii ± 1.3 y Pubertal F: eleven.4 ± one.9 y Pubertal M: 12.2 ± one.4 y Mail service-pubertal F: fifteen.3 ± ane.6 y Mail service-pubertal Grand: 15.eight ± 1.6 y | All F: Fat (%)=1.33 (tric+subsc) − 0.013 (tric+subsc)2 − 2.5 Prepubertal M: Fatty (%)=1.21 (tric+subsc) − 0.008 (tric+subsc)ii − i.vii Pubertal M: Fat (%)=1.21 (tric+subsc) − 0.008 (tric+subsc)2 − 3.4 Post-pubertal M: Fat (%)=one.21 (tric+subsc) − 0.008 (tric+subsc)2 − five.5 All F when (tric+subsc) > 35 mm: Fat (%)=0.546 (tric+subsc) + nine.7 All Grand when (tric+subsc) > 35 mm: Fat (%)=0.783 (tric+subsc) + 1.7 F: Fat (%)=0.61 (tric+calf) +v.ane 1000: Fat (%)=0.735 (tric+dogie) + ane |
| Lean et al. (1996) | eighteen−64.3 y | F: Fatty (%)=0.730 BMI + 0.548 tric + 0.270 Age − v.9 M: Fat (%)=0.742 BMI + 0.95 tric + 0.335 Age − 20 |
| Bray et al. (2001) | 10 y | Thousand and F: Fat (%)=7.66 + 0.22 subsc + 0.21 thigh + 0.64 biceps + 0.31 calf Yard and F: Fat (%)=8.71+ 0.19 subsc + 0.76 biceps + 0.18 suprai + 0.33 tric |
F: females, M: males, y: years, D: density (kg/l), BMI: torso mass alphabetize (kg/m2), sum of four skinfolds: biceps + triceps+ subscapular + suprailiac (mm), age (years), tric: triceps skinfold (mm), biceps: biceps skinfold (mm), subsc: subscapular skinfold (mm), suprai: suprailiac skinfold (mm), thigh: thigh skinfold (mm), calf: calf skinfold (mm).
Source: Rodriguez et al. (2005).
Some equations for children and adolescents have been compared with the criterion 4-component model, meet Table 3. Significant bias for percentage torso fat and fat free mass was observed for the equations by Slaughter et al. (1988), Johnston et al. (1988) and Beck (1971). No significant mean bias was shown by the equation past Deurenberg et al. (1990), but the bias was correlated significantly to fatness and limits of agreements were wide indicating that individual values are non accurate. This may affect the evaluation of trunk composition changes inside individuals overtime.
Tabular array 3 Bias and 95% limits of understanding for % body fat predicted using skinfold-thickness equations confronting measurements fabricated with the 4-component model.
| Equation | | | |
|---|---|---|---|
| Slaughter et al. (1988) | | | |
| Pct body fatty (%) | | | |
| Johnston et al. (1988) | | | |
| Percentage body fat (%) | | | |
| Deurenberg et al. (1990) | | | |
| Per centum body fat (%) | | | |
| Brook (1971) | | | |
| Percentage body fat (%) | | | |
iBias was calculated as skinfold-thickness values minus values from use of the 4C model. Correlations were calculated as the correlation between the difference and hateful. 95% limits of agreement calculated as ± 2SD of the difference between techniques. FFM values were log transformed to limited the difference as a percentage of the mean. Values for pct trunk fat are expressed as a percentage of trunk weight.
2 P < 0.0001.
3 P < 0.005.
Adapted from: Wells et al. (1999).
Infancy
There are limited equations to use in infancy to derive % body fat and they tend to be population or age specific (e.grand. first x days of life) and based on different skinfold thickness measuring sites.
- Dauncey et al. (1977) in the 4 months of life, based on ii sites (subscapular and triceps), ethnicity not defined.
- Sen et al. (2010) in 6-24 months Indian Infants based on 3 sites (biceps, triceps and suprailiac) plus arm circumference.
- Schmelzle et al. (2002) in 1-x days old White German Infants based on 4 sites (subscapular, biceps, triceps and suprailiac) However, the reference method used was DEXA which has not been directly validated in neonates for body limerick assessment. DEXA validation studies in infancy are based on a piglet model.
- Deierlein et al. (2012) in 1-iii days old multi-ethnic population based on 4 sites (triceps, subscapular, flank, and thigh).
- Catalano et al. (1995) in one-2 days old American infants of white, black and Hispanic ethnicities based on 1 site (flank). However, the reference method used was TOBEC, which has not been direct validated in neonates for torso limerick assessment. Cantankerous-validation studies would be required to make up one's mind the accuracy of these equations in predicting % body fat in other neonates and infants populations.
- Aris et al. (2013) in ane-three days onetime Asian infants, based on ane site (subscapular).
The Deierlein et al. (2012), Catalano et al. (1995) and Aris et al. (2013) equations accept been evaluated using air displacement plethysmography (PEABOD) at nativity and 3 months, demonstrating significant bias for body fat in the equation by Catalano et al. (1995) at birth, and significant bias for torso fatty at 3 months for all the equations.
Tabular array 4 Bias and 95% limits of understanding for % body fat predicted using skinfold-thickness equations confronting measurements made with the 4-component model.
| Equation | | | ||||||
|---|---|---|---|---|---|---|---|---|
| | | | | | | | | |
| Birth | ||||||||
| Deierlein | | | | | | | | |
| Catalano | | | | | | | | |
| Aris | | | | | | | | |
| 3 months | ||||||||
| Deierlein | | | | | | | | |
| Catalano | | | | | | | | |
| Aris | | | | | | | | |
*Significance for the correlation of the force for the relationship between the mean of the benchmark and each equation correlated to the deviation between the equations estimated infant fat mass and the criterion measured fat mass. A non-significant correlation suggests no bias in the technique across the range of fatness.
Source: Clauble et al. (2016).
Equations derived in children have also been used to estimate % body fat in infancy, such as Deurenberg et al. (1989) and Slaughter et al. (1988). However, the relationship between total body-density and skinfold thickness varies with age and those equations may not be applicable in younger groups.
Estimates derived using the Slaughter et al. (1988) equation take been compared to those from air displacement plethysmography (PEABOD) at 6 weeks and at 4.5 months of age, and to those from DEXA at four months. Agreement analysis showed significant bias at 6 weeks, underestimating percentage trunk fat by 2·four–viii·nine %. At 4.v months, the underestimation was greater in infants with the highest body fat. The limits of agreement were wide; error ranged from 18 % fat beneath to 9 % fatty above the PEA POD measurement. The understanding assay between Slaughter et al. (1988) and DEXA shows a considerable systematic bias which increases with increasing % body fatty. The equation overestimated % torso fat by 10.7% when compared to the PEAPOD measurement (Lingwood et al., 2012; Schmelze et al., 2002).
Estimates derived from the Deurenberg et al. (1989) equation have been compared to those from DEXA at 4 months of historic period. The equation overestimated % body fat past 6.27% when compared to the DEXA measurement (Schmelze et al., 2002).
When analysing data in infancy, often the raw thickness data are used. The sum of the thicknesses is determined and internal standard departure score (Z-score) are derived. Internal Z-scores tin can be generated by regressing skinfolds on age (and using the saved residuals), and then adjusting for sexual activity in the analyses.
Skinfold thickness-for-age indices
The skinfold indices - triceps skinfold-for-age and subscapular skinfold-for-age - are useful add-on to the battery of growth standards for assessing babyhood obesity in infants betwixt 3 months to 5 years.
These indices are expressed in percentiles (percentage of median) and can be assessed by the percentile point achieved past a child relative to the healthy children of that age and gender in the same population. Median is regarded equally a reference value, and 3rd and 97th percentiles as thresholds to indicate abnormally depression or abnormally high values.
The indices tin likewise be expressed as Z-score derived by using the formula:
(Measured value – Boilerplate value in the reference population) / Standard departure of the reference population
The WHO growth standard (2006) for triceps skinfold-for-historic period and subscapular skinfold-for-age are used for interpretation.
An overview of skinfold thickness methods is outlined in Table v.
Strengths
- Inexpensive
- Not-invasive
- fiddling space required
- portable
- simple to obtain in near historic period groups including infants
- Estimates of body composition from skinfolds correlates well with those derived from the reference methods, underwater weighing
- The use of a standardized protocol increases the reliability of skinfold thickness measurement
- Intra-observer and inter-observer errors are low compared to between‐private variability
- Peradventure the sole tool to assess torso composition changes in infancy and in early childhood, where other methods like the Peapod are not viable
- Skinfolds are specially useful in monitoring changes in fatness in children considering of their small body size, and the majority of fat is subcutaneous even in obese children
- Convenient and price-effective ways of monitoring changes in body composition of large groups over time
Limitations
- Accuracy dependent on the technician's skill also every bit the blazon of caliper and the skinfold prediction equation used
- The reliability of the measurements decreases with increasing thickness
- Cheaper plastic calipers accept a less precise measuring scale, and oft provide variable pressure and a smaller range of measurement
- Accuracy and precision are poorer in obese individuals as it is difficult to hold a large skinfold while reading the caliper dial
- Near skinfold calipers accept an upper measurement limit of 45 to threescore mm, which restricts their apply to overweight and obese individuals.
- The majority of national reference information available are for skinfolds at the triceps and subscapular locations. The triceps skinfold varies considerably by sex and tin can reflect changes in the underlying triceps musculus rather than an actual change in trunk fatness.
- Measurement accuracy influenced past tension in the skin
- Hydration level tin influence the measurements. Dehydration reduces the skinfold size. Exercise inflates the skinfold size equally overheat causes a shift in body fluids to the skin. Oedema and dermatitis increment the skinfold size.
- Assumes that the thickness of subcutaneous fat is constant or predictable within and betwixt individuals
- Assumes that body fat is normally distributed
- Unable to accurately evaluate body composition changes within individuals overtime.
- Highly skilled technicians are required
- Available published prediction equations may not always exist applicable to a report population and cross validation in a sub-sample of a study population is required before application of those equations
Table five Characteristics of skinfold thickness methods.
| Consideration | Comment |
|---|---|
| Number of participants | Large |
| Relative cost | Low |
| Participant burden | Low |
| Researcher burden of data drove | Medium equally method requires highly trained observers |
| Researcher burden of coding and data analysis | Low |
| Chance of reactivity bias | No |
| Risk of recall bias | No |
| Chance of social desirability bias | No |
| Risk of observer bias | Yes |
| Space required | Low |
| Availability | High |
| Suitability for field utilise | High |
| Participant literacy required | No |
| Cognitively enervating | No |
Considerations relating to the use of skinfold thickness methods in specific populations are described in Table half-dozen.
Tabular array half-dozen Utilise of skinfold thickness methods in different populations.
| Population | Comment |
|---|---|
| Pregnancy | Suitable, merely estimates of body fat changes derived from skinfolds are prone to measurement error, especially during pregnancy due to hydration level. Rapid decreases in measurement occur postpartum that are likely attributable to changes in hydration post-obit delivery rather than marked changes in subcutaneous fatty |
| Infancy and lactation | Suitable |
| Toddlers and young children | Suitable |
| Adolescents | Suitable |
| Adults | Suitable |
| Older Adults | Suitable, just presence of oedema may impact estimates |
| Ethnic groups | Suitable |
| Other (obesity) | Suitable, only difficult to become reliable measurements, particularly in those cases in which skinfold thickness approach the upper limit of the measurement range of the caliper |
To obtain reliable data from this method information technology is essential to standardize the procedure, train the participating staff and assess inter and intra observer reliability to monitor measurement error.
Refer to section: practical considerations for objective anthropometry
Source: https://dapa-toolkit.mrc.ac.uk/anthropometry/objective-methods/simple-measures-skinfolds
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