Anthropometric Measurements

• Anthropometric measurements are non-invasive quantitative assessments of the body.
• Anthropometric measurements in adults provide information about nutritional status, obesity, health/dietary status, future disease risk, and body composition.
• Anthropometric measurements in children provide information about nutritional status, general health status, nutritional adequacy, and growth/developmental patterns.

Common Anthropometric Measurements

• Common measurements include hydrostatic weighing, Body Mass Index (BMI), waist/hip circumference measurements, skinfold testing, limb length, and head circumference (in pediatric patients).
• Body composition is a breakdown of an individual's weight by percentages of fat, muscle, bone, and water.

Hydrostatic Weighing

• Hydrostatic weighing calculates body density by comparing dry weight to weight when submerged.
• It is the gold standard for body density testing but is not typically done in the clinic.
• Hydrostatic weighing is used for athletes and research.
• Formulas are available to calculate body fat percentage from hydrostatic weighing results.
• The principle of hydrostatic weighing can be applied to limb volume measurements.

Water Displacement – Limb Volume

• The concept of water displacement measures limb volume.
• Water displacement is used for patients with lymphedema, swelling, and for athletes to measure muscle mass.
• Water displacement is an easy, quick, affordable, and accurate method.

Body Mass Index (BMI)

• BMI is the ratio of body weight to height² and provides a numerical measure of body composition.
• BMI categorization is based on weight deviations from normal for a given height.
• Excess weight or deficiency may be accounted for by body fat in BMI calculations.
• Underweight is classified as a BMI of less than 18.4.
• Normal weight is classified as a BMI between 18.5 and 24.9.
• Overweight is classified as a BMI between 25 and 29.9.
• Obese is classified as a BMI between 30 and 34.9.
• Severely obese is classified as a BMI between 35 and 39.9.
• Very severely obese is classified as a BMI of greater than 40.

Limitations of BMI

• BMI is commonly used but has significant limitations.
• BMI was originally derived to measure population health, not individual health.
• BMI does not account for tissue type.
• BMI correlates with body fat percentage but is not a direct measure of body composition.
• BMI does not account for body fat variability with age, gender, or ethnicity.
• BMI isn't as accurate for athletes or geriatric populations.

Waist Circumference Measurements

• Waist circumference is measured at the level of the ilium.
• Measuring waist circumference is useful in adults and children.
• Measuring waist circumference gives a direct measure of central adiposity.
• A high waist circumference is associated with increased risk of type 2 diabetes, hypertension, and coronary artery disease.
• CDC Risk Cutoffs:
  • Men: >40 inches
  • Women: >35 inches

Waist Circumference Limitations

• Waist circumference should be used as a screening tool.
• It is possible to have a normal body weight, but an abnormal waist circumference.
• Waist circumference measurements do not provide information about overall health of the individual.
• Waist circumference measurements do not provide information about Body fat percentage/body composition.

Waist-Hip Ratio

• Waist-hip ratio is the circumference of the waist in relation to the circumference at the hips.
• Hip circumference is measured at the level of the greater trochanter.
• Waist-hip ratio is reported as W/H.
• It is also used as an indicator of developing health conditions.
• WHO W/H Ratios for Obesity:
  • Men: >1.00
  • Women: >0.85

Skinfold Testing

• Skinfold testing is a commonly used method of measuring the thickness of the skin and subcutaneous fat with calipers.
• Body density and fat % can then be calculated based of the measurements obtained.
• Accurate skinfold testing is highly correlated with hydrostatic weighing.
• Technique is important in skinfold testing
• Skinfold testing sites include abdomen, triceps, biceps, chest/pecs, medial calf, midaxillary, subscapular, suprailiac, and thigh.
• Composite thickness at these sites is then used to calculate body fat % based with relation to age

Limb Length

• Objective measurement of length of a bony segment
• Limb length measurements utilize known landmarks with a tape measure, calipers, or imaging.
• Limb length measurements are useful for determining asymmetries in growth and development.
• Limb length measurements confirm observed deficiency in length.
• Limb length measurements may be used as a pre/post intervention measure.
• Limb length may relate to chronic illness.
  • Short thigh length = higher prevalence of metabolic syndromes
  • Short upper arm length = higher prevalence of diabetes

Leg Length Discrepancy

• Functional leg length discrepancy is an asymmetric leg length due to altered mechanics that results in the appearance of a "short" leg, when a bony asymmetry does not exist
• A true leg length discrepancy exists between the head of the femur and the ankle.
• The typical cut-off for interventions due to leg length discrepancy is around 1½".

Head Circumference

• Head circumference measures an infant's head size to assess growth and CNS development.
• Head circumference is seen as a very important measure that is quick and reliable, and common in children under 4 years old.
• Head circumference determines brain size.
• Head circumference measurements are plotted in comparison to age and sex-matched norms.
• Microcephaly = 2 SD below mean

Head Circumference – Clinical Relevance

• Brain weight correlates directly with head circumference.
• Total brain DNA content (# of cells) is linearly related to changes in head circumference from 0-6mo.
• Brain growth is rapid from 0-2 years and slows around age 4.

Anthropometric Errors

• Errors in BMI, weight, and abdominal obesity (waist circumference) are higher in obese individuals.
• Measurements requiring circumference are more prone to errors.
• Training does not significantly decrease errors outside of skin folds.

Considerations for Anthropometric Testing

• Limited contraindications
• Utility is mostly for monitoring health status/growth, determining risk
  • Should be tracked over time
  • Should NOT be used as an indicator of acute disease state
• Can be applied to a wide range of the population
• Clinical applicability of "gold-standards"?