Skinfold Measures

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Skinfold Measures

• Chapter 8 4

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Skinfold Measures

• Skinfold thickness provides a good measure of
  subcutaneous fat.
• Sum of several skinfold measures can be used to
  estimate total body fat.

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Skinfold Measures

• Skinfolds include skin and SAT, the latter
  consisting of adipocytes that contain
  triglycerides and connective tissue that includes
  blood vessels and nerves.

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Skinfold Measures

• The thickness of a double layer of skin is about
  1.8 mm, but this varies among individuals and
  systematically by site and with age.

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Skinfold Measures

• Women have thinner skinfolds than men and the
  elderly have thinner skinfolds than young adults
• (At fixed body density and BF)

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Skinfold Measures

• Variations in skin thickness among individuals
  affect the validity of skinfold thickness

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Skinfold Measures

• The paucity of SAT in the lean can make it
  difficult to elevate a fold, and it is not easy
  to elevate folds with parallel sides in those
  with large amounts of SAT.

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Skinfold Measures

• Skinfold thicknesses are less precise than
  circumferences in overweight individuals than in
  general populations

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Skinfold Measures

• Affected by individual and regional differences
  in compressibility that vary with age, gender,
  and recent weight loss.

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Skinfold Measures

• The pressure exerted by the calipers displaces
  some extracellular fluid.

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Skinfold Measures

• Pressure from skinfold calipers may force some
  adipose tissue lobules to slide into areas of
  lesser pressure
• This sliding may be more marked for thick
  skinfolds in which the adipose tissue contains
  little connective tissue.

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Caliper Comparison
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Caliper Comparison
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Skinfold Measures

• Factors to be considered in the selection of
  skinfold sites
• accessibility in relation to undressing,
• precision,
• availability of reference data,
• thickness of the fold,
• (important in overweight subjects)

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Skinfold Measures

• May be impossible to measure skinfold thickness
  in overweight subjects because thickness may
  exceed maximum jaw openings of calipers.

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Skinfold Measures

• Measurements can be made at sites where there is
  little SAT (e.g., biceps), or ultrasound can be
  used to measure SAT thickness

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Skinfold Measures

• Skinfold thicknesses have low correlations with
  FFM (about 0.2), but they are highly correlated
  with BF (r 0.7 to 0.9)

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Skinfold Measures

• No one skinfold thickness is an accurate
  predictor of BF.

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Skinfold Measures

• This reflects individual variation in the
  distribution of SAT and in the proportion of the
  total adipose tissue that is subcutaneous.

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Skinfold Measures

• There are gender- and age-differences in the
  relationships of skinfold thicknesses to BF.
• Only three or four skinfold thicknesses are
  needed in predictive equations.

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Skinfold Measures

• In children, skinfold thicknesses are better
  predictors of body density than are
  circumferences.

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Skinfold Measures

• The use of skinfold thicknesses to predict BF
  from densiometry is based on implicit assumptions
  that
• measurements of skinfold thicknesses at a few
  sites provide an adequate description of SAT
• there is a fixed relationship between SAT and DAT.

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Skinfold Measures

• The first assumption appears correct

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Skinfold Measures

• Specific predictive equations are needed for
  children and adolescents

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Skinfold Measures

• Jackson and Pollock equation to developed from a
  group that was slightly taller and lighter than
  U.S. national data.

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Skinfold Measures

• Jackson et al. equation to predict body density
  for young women, was from a group slightly taller
  and lighter than U.S. national data

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Skinfold Measures

• Skinfold equations derived from young adults
  commonly underpredict BF in the middle-aged and
  elderly.

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Skinfold Measures

• Vu Tran and Weltman reported an equation to
  predict BF in middle-aged men.

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Skinfold Measures

• In the obese, the proportion of total adipose
  tissue that is subcutaneous may be lower than in
  general populations and extracellular fluid is
  increased.

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Skinfold Measures

• Equations are needed that are specific for the
  obese.
• There is evidence that these equations should be
  based on circumferences rather than skinfold
  thicknesses.

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Skinfold Measures

• Teran developed an equation to predict BF
  calculated from body density using a
  two-component model in obese women aged 18 to 50
  years.

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Skinfold Measures

• Equations to predict BF calculated from body
  density with a two-component model may be
  inaccurate

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Skinfold Measures

• Ethnic differences in the distribution of SAT
  indicate that skinfold equations are likely to
  perform poorly when applied to ethnic groups
  other than those from which they are derived.

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Skinfold Measures

• Equations are specific for ethnic groups.

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Skinfold Measures

• Predicted values are less accurate than observed
  (calculated) values
• A predictive equation should not be applied to a
  group that is markedly different from the group
  used to develop the equation.

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Skinfold Measures

• Important group differences may relate to age,
  gender, ethnicity, and level of body fatness.

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Summary

• SF thicknesses have low correlations with FFM (r
  .2)
• Their correlations with BF are higher (r .7 to
  .9)
• No single site is an accurate predictor of BF

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Common Sites

• Truncal
• Subscapular
• Midaxillary
• Abdominal
• Supriliac
• Pectoral

• Appendicular
• Anterior Thigh
• Medial Calf
• Posterior Calf
• Triceps
• Biceps