anthropometry

• Nutritional Anthropometry


  Measurements of the variations of the physical dimensions and the gross composition of the human body at different age levels and degrees of nutrition
• Anthropometric methods


  Involve measurements of the physical dimensions and gross composition of the body
• Objectives of Anthropometric Measurements

  • Identify mild, moderate, severe states of malnutrition
  • Identify individuals and populations at risk to malnutrition
  • Evaluate changes in nutritional status over time
  • Serve as proxy indicators of constraints to human welfare
  • Monitor nutritional problems
  • Evaluate the impact of interventions designed to enhance nutrition, health, economic and/or environmental factors
• Advantages of anthropometry measurements in nutritional assessment

  • Simple, safe, noninvasive techniques
  • Inexpensive equipment required
  • Relatively unskilled personnel can perform the measurement procedures
  • Methods can be precise and accurate
  • Retrospective information is generated on past long-term nutritional history
  • Mild to moderate undernutrition, as well as severe states of under- or overnutrition, can be identified
  • Changes in nutritional status over time and from one generation to the next can be evaluated
  • Screening tests that identify individuals at high risk to under- or overnutrition can be devised
• Limitations of anthropometric measurements

  • Relatively insensitive to detect changes in nutritional status over short periods of time
  • Cannot identify any specific nutrient deficiency
  • Non-nutritional factors can lower the specificity and sensitivity
• Two types of anthropometric measurements

  • Body size
  • Body composition
• Body size measurements


  Most widely used measurements of body size are stature, weight, and head circumference
• Body composition measurements


  Based on the classical "two component model" - fat mass and fat free mass
• Skinfold Thickness


  The size of the subcutaneous fat depot provides an estimate of total body fat
• Assumptions in the estimation of total body using skinfold thicknesses: the thickness of the subcutaneous adipose tissue reflects a constant proportion of the total body fat, the sites represent the average thickness of the subcutaneous adipose tissue, age and disease state can affect the distribution of fat
• Common Sites for Skinfold Measurement

  • Triceps
  • Biceps
  • Subscapular
  • Suprailiac
  • Midaxillary
• Combination of triceps skinfold and mid-upper-arm circumference


  Can be used to estimate mid-upper-arm fat area and mid-upper-arm muscle circumference or area, surrogates for total body fat content, and muscle mass, respectively
• Waist-Hip Ratio (WHR)


  An index of the distribution of body fat which can be measured more precisely than skinfolds
• Regardless of overall obesity, central obesity is considered a risk factor in the development of certain diseases, such as coronary heart disease and type 2 diabetes mellitus
• The accuracy of waist and hip circumference measurements depends on the tightness of the measuring tape, and on its correct positioning
• Waist circumference alone could replace waist-hip ratio and BMI as a single risk factor for all-cause mortality
• A moderate WHR, according to the World Health Organization (WHO), is 0.9 or less in males and 0.85 or less in women. A WHR of 1.0 or greater raises the risk of heart disease and other diseases connected to being overweight in both men and women
• Waist-Hip Circumference Ratio (WHR)

  Waist circumference and waist-hip ratio are both related to increased risk of all-cause mortality, throughout the range of adult BMIs
• Waist-Hip Circumference Ratio (WHR)


  • Waist circumference and waist-hip ratio are strongly predictive in young and middle aged adults compared to older people and those with low BMI
• Waist circumference


  Could replace waist-hip ratio and BMI as a single risk factor for all-cause mortality
• Moderate WHR


  0.9 or less in males and 0.85 or less in women (according to WHO)
• High WHR


  1.0 or greater raises the risk of heart disease and other diseases connected to being overweight in both men and women
• Mid-upper arm circumference (MUAC)


  Reflects total body muscle mass and muscle tissue changes, index of protein reserves
• Mid-upper-arm muscle circumference (MUAMC)


  Both MUAC and triceps skinfold thickness are used in deriving the muscle circumference of the mid-upper arm
• Mid-upper-arm muscle area (MUAMA)

  Reflects magnitude of muscle tissue change
• MUAC


  Useful in diagnosing protein-energy malnutrition when the amount of subcutaneous fat is small, as changes in muscle mass are paralleled by changes in MUAC
• MUAC cut-off points for screening in the community for SAM and MAM

  • Children under five: 11-11.9 cm Moderate acute malnutrition (MAM), <11 cm Severe acute malnutrition (SAM)

  Pregnant women/adults: 17-21 cm Moderate malnutrition, 18-21 cm with recent weight loss Moderate malnutrition, <17 cm Severe malnutrition, <18 cm with recent weight loss Severe malnutrition
• MUAC is valuable in screening for protein-energy malnutrition, especially when the measurement of height and weight may not be feasible
• Errors in anthropometry can be random measurement errors or systematic measurement errors
• Random measurement errors


  Deviations from the correct result due to chance alone, generated when the same examiner repeats the measurements (within- or intra-examiner error) or when several different examiners repeat the same measurement (between- or inter-examiner error)
• Systematic measurement errors


  Errors that cause a result to depart from the true value in a consistent direction, reducing the accuracy of a measurement
• Sources of random measurement errors

  • Individual biological variation
  • Sampling error
  • Measurement error
• Technical error of measurement (TEM)


  The square root of the measurement error variance, expressed in the same units as the anthropometric measurement, related to the anthropometric characteristics of the study group
• Percentage TEM


  Analogous to the coefficient of variation, calculated as (TEM/mean) x 100%, allows direct comparisons of all types of anthropometric measurements
• Coefficient of reliability (R)


  Indicates the proportion of between-subject variance in a measured population which is free from measurement error, ranges from 0 to 1
• Correlation coefficient (r) and intraclass correlation (ICC) can also be used to assess reliability
• Systematic errors reduce the accuracy of a measurement by altering the mean or median value, without affecting the variance or precision
• Coefficient of variation (CV)


  Measure of the variability in a measured population which is free from measurement error. CVs of 5% or less generally give us a feeling of good method performance, whereas CVs of 10% and higher are bad.
• Coefficient of reliability (R)


  Measure of the proportion of the variance that is due to factors other than measurement error. A measurement with R = 0.95 indicates that 95% of the variance is due to factors other than measurement error.
• Correlation coefficient (r)


  Also used to assess reliability, can be computed using intra class correlation (ICC) to demonstrate the strength of the relationship (similarities) between two measurements.