Introduction to Anthropometry
Anthropometry is a branch of science that involves the systematic collection of quantitative measurements of the human body. These physical measurements serve as vital indicators of an individual's health, nutritional adequacy, and growth patterns across different life stages. Health professionals and researchers rely on anthropometry for a wide range of applications, from monitoring a child's development against growth charts to assessing an adult's risk for chronic diseases associated with obesity. While many different measurements can be taken, five core components are frequently used to provide a comprehensive health assessment.
The Five Anthropometric Measurements
1. Height and Weight
Height and weight are the two most fundamental anthropometric measurements, serving as the basis for many other health indicators, such as Body Mass Index (BMI). Height, or stature, is a measure of a person's total vertical reach, while weight measures their body mass.
Measurement methods:
- Height: A stadiometer is used for individuals who can stand, with the person standing straight with their heels, buttocks, and shoulder blades against the back of the instrument. For infants and toddlers under two years of age, recumbent length is measured on an infantometer.
- Weight: A calibrated digital or beam scale is used, with the individual standing still in the center of the scale with an even weight distribution. For infants, a specific infant scale is used.
2. Body Mass Index (BMI)
Body Mass Index (BMI) is a calculated anthropometric index derived from height and weight that is used to categorize an individual's weight status. It is a simple and quick screening tool for potential weight-related health issues. BMI is calculated using a standard formula: $BMI = weight(kg) / height(m)^2$.
Key considerations for BMI:
- It is not a direct measure of body fat and has limitations, especially in populations with high muscle mass (like athletes) or in the elderly where fat distribution changes.
- For children and adolescents, BMI is plotted on age- and gender-specific growth charts, as their body composition changes over time.
- In adults, specific BMI ranges correspond to categories such as underweight, normal weight, overweight, and obese.
3. Body Circumferences (Waist and Hip)
Body circumference measurements are used to assess body fat distribution, which can provide more insight into health risks than BMI alone. The most common measurements are the waist and hip circumferences, which are often used together to calculate the waist-to-hip ratio (WHR).
How to measure:
- Waist Circumference: Measured at the narrowest point of the abdomen, located between the lowest rib and the iliac crest.
- Hip Circumference: Measured at the widest point of the buttocks.
The resulting waist-to-hip ratio is a strong predictor of risk for conditions like heart disease and diabetes, as it reflects central adiposity (abdominal fat).
4. Skinfold Thickness
Skinfold thickness is a method used to estimate body fat percentage by measuring the thickness of subcutaneous adipose tissue at specific sites on the body using calipers. Common sites include the triceps, biceps, subscapular (under the shoulder blade), and suprailiac (above the hip bone).
Importance of skinfold measurements:
- It helps differentiate between fat mass and lean body mass, providing a more detailed picture of body composition.
- The technique requires skill to perform accurately, and the resulting data is typically interpreted using population-specific equations.
5. Mid-Upper Arm Circumference (MUAC)
Mid-Upper Arm Circumference (MUAC) is a measure of the circumference of the upper arm at its midpoint. It is particularly useful and widely adopted for assessing malnutrition and wasting in children aged 6 to 59 months, as well as in emergency settings. A MUAC measurement of less than 12.5 cm in children is often a sign of severe malnutrition.
How MUAC is measured:
- The measurement is taken on the left upper arm, halfway between the shoulder (acromion) and elbow (olecranon), using a specialized, non-stretchable tape.
- The simplicity and portability of MUAC tape make it an invaluable tool for field-based nutritional assessments.
Comparison of Anthropometric Measurements
| Measurement | Primary Purpose | Best Used For | Equipment Needed | Advantages | Limitations |
|---|---|---|---|---|---|
| Height & Weight | General growth tracking and calculating BMI | Infants, children, and adults | Calibrated scale, stadiometer or infantometer | Easy, inexpensive, widely applicable | Cannot differentiate fat from muscle; less meaningful in isolation |
| BMI | Screening for overweight and obesity | Adults and children (using charts) | Scale, stadiometer | Simple calculation, standard cut-offs | Less accurate for muscular individuals or the elderly |
| Waist & Hip Circumference | Assessing body fat distribution and chronic disease risk | Adults, especially those at risk for heart disease | Non-stretchable tape measure | Better indicator of abdominal (visceral) fat risk than BMI | Highly dependent on measurement technique; can be influenced by clothing |
| Skinfold Thickness | Estimating body fat percentage | Athletes, fitness enthusiasts | Calipers | More detailed body composition estimate than BMI | High variability; requires training for accuracy |
| Mid-Upper Arm Circumference | Screening for acute malnutrition | Children (6-59 months), elderly, emergency populations | Non-stretchable MUAC tape | Simple, portable, rapid assessment tool | May be influenced by hydration status (edema) |
