Anthropometry Comprehensive Study Notes

Definition & Core Concept

  • Anthropometry derives from Greek roots: “Anthropos” (man) + “Metron” (measurement).

  • Branch of anthropology devoted to quantitative assessment of human body size, proportion & composition.

  • Universally applicable, inexpensive, portable, non-invasive.

  • Reflects present nutritional status (cannot clearly distinguish acute vs. chronic changes).

  • Equally useful for detecting under- and over-nutrition.

Practical Uses

  • Individual level

    • Screening (single visit) in emergencies & routine care.

    • Growth monitoring (serial/longitudinal).

  • Population level

    • One-time surveys (e.g., during food crises, baseline studies).

    • Nutritional surveillance (trend detection, early warning, programme planning & evaluation).

Significance in Health

  • Primary tool for detecting past or current malnutrition, especially in children.

  • Differentiates stunting (chronic) vs. wasting (acute).

  • Detects Protein-Energy Malnutrition (PEM) & obesity.

  • Monitors effect of nutrition/clinical interventions.

  • Hospital use: flags Chronic Energy Deficiency (CED) or excess weight.

  • Routine public-health screening & programme targeting.

Advantages vs. Disadvantages

  • ✅ Simple, safe, low-cost, portable instruments; minimal training.

  • ✅ Generates precise, accurate, numerical data; good reflection of long-term history.

  • ❌ Relatively insensitive to short-term change or single-nutrient deficiency.

  • ❌ Cannot always discern nutrition-induced vs. non-nutrition-induced growth failure.

  • ❌ Inter-observer error; dependence on reference standards & arbitrary cut-offs.

Age-Dependent & Age-Independent Parameters

  • Age-Dependent: Weight, Height/Length, Head & Chest circumference.

  • Age-Independent (1–5 y): Mid-Arm Circumference, Weight-for-Height, Skinfolds, MUAC/Height ratio.

Growth Velocity & Expected Weights

  • Typical monthly/annual weight gain:

    • 0–4 mo: 1.0 kg⋅mo−11.0\text{ kg·mo}^{-1} (≈30 g⋅d−130\text{ g·d}^{-1})

    • 5–8 mo: 0.75 kg⋅mo−10.75\text{ kg·mo}^{-1}

    • 9–12 mo: 0.5 kg⋅mo−10.5\text{ kg·mo}^{-1}

    • 1–3 y: 2.25 kg⋅yr−12.25\text{ kg·yr}^{-1}

    • 4–9 y: 2.75 kg⋅yr−12.75\text{ kg·yr}^{-1}

    • 10–18 y: 5–6 kg⋅yr−15–6\text{ kg·yr}^{-1}

  • Milestones:

    • 4–5 mo: weight doubles birth weight.

    • 1 y: triples; 2 y: quadruples; 7 y: ×7 birth weight.

Predictive Formulae

  • Weech

    • 3–12 mo: Wt (kg)=Age (mo)+92\text{Wt (kg)} = \frac{\text{Age (mo)} + 9}{2}

    • 1–6 y: Wt (kg)=2×Age (y)+8\text{Wt (kg)} = 2\times \text{Age (y)} + 8

    • 7–12 y: Wt (kg)=7×Age (y)−52\text{Wt (kg)} = \frac{7\times \text{Age (y)} - 5}{2}

  • Desirable Body Weight (DBW) – Infants

    • 0–6 mo: DBW (g)=Birth Wt+(Age (mo)×600)\text{DBW (g)} = \text{Birth Wt} + (\text{Age (mo)}\times 600)

    • 7–12 mo: DBW (g)=Birth Wt+(Age (mo)×500)\text{DBW (g)} = \text{Birth Wt} + (\text{Age (mo)}\times 500)

    • If birth weight unknown: assume 2500 g (preterm) or 3000 g (term).

    Example (full-term, 32 wk = 8 mo):
    DBW=3000+(8×500)=7000 g=7 kg\text{DBW} = 3000 + (8 \times 500) = 7000\text{ g} = 7\text{ kg}
    Alternative quick rule: DBW (kg)=Age (mo)2+3\text{DBW (kg)} = \frac{\text{Age (mo)}}{2} + 3 ➜ 82+3=7\frac{8}{2}+3 = 7 kg.

Core Anthropometric Measurements

Weight

  • Most sensitive indicator of current status; reflects short-term deficits.

  • Instruments: Beam balance, electronic infant scale, Salter spring scale (field), bathroom scale (avoid).

  • Infant Salter procedure: zero scale, remove heavy clothes, suspend child via sling, read to 0.1 kg.

  • Adult beam balance: remove heavy garments; centre on platform; align beams; record to 0.1–0.2 kg.

  • Caveats: calibration, minor weight changes from feeds, urine, dehydration, etc.

Height / Recumbent Length

  • Height (≥2 y, standing); Length (<2 y, supine) via stadiometer or infantometer.

  • Technique (infant): head against fixed board, legs fully extended, feet at 90∘90^{\circ}; read to 1 mm.

  • Technique (child): heels, buttocks, shoulders, occiput touch wall; head in Frankfurt plane; mark vertex.

  • Indicator of chronic status; low height ⇒ prolonged under-nutrition (stunting).

Head Circumference (OFC)

  • Tape over occipital protuberance & supra-orbital ridge; measure till 5 y.

  • Growth: +12 cm in first year; +5 cm from 1–5 y; adult size by ~6 y.

  • Norms: Birth 34–35 cm34–35\text{ cm}; 1 y 45–46 cm45–46\text{ cm}; 5 y 50–51 cm50–51\text{ cm}.

  • Microcephaly: >3 SD below mean; Macrocephaly: >2 SD above.

Chest Circumference

  • Measured at nipples (mid-inspiration). ≤5 y supine; >5 y standing.

  • Birth: head > chest by ≤3 cm; parity reached ~9–12 mo then chest outgrows head.

  • Head ≫ chest (>3 cm) common in preterms, SFD & hydrocephalus; in malnutrition chest lag persists.

Mid-Upper Arm Circumference (MUAC/MAC)

  • Relatively age-independent 1–5 y; normal healthy 15–17 cm.

  • Site: midway between acromion & olecranon (left arm preferred); arm relaxed.

  • Cut-offs (WHO):

    • <12.5 cm12.5\text{ cm} – severe under-nutrition.

    • 12.5–13.5 cm12.5–13.5\text{ cm} – moderate/risk.

    • >13.5 cm13.5\text{ cm} – adequate.

  • Tools: fibre-glass tape, Shakir (colour-coded), 4 cm bangle test (passes = <12.5 cm).

Skin-Fold Thickness (SFT)

  • ≈50 % of body fat is subcutaneous; SFT predicts total fat.

  • Calipers: Harpenden (gold standard), Holtain, Lange, etc.

  • General steps: grasp fold, apply caliper 1 cm distal, hold 3–4 s, read mm, take 3 readings.

  • Key sites & norms:

    • Triceps (posterior midpoint humerus): 6–12 mm (lean) – 40–50 mm (obese).

    • Subscapular: 1 cm below inf. scapular angle.

    • Supra-iliac: 5 cm above ASIS, angled 45° medially.

    • Biceps (anterior midpoint).

  • Children 1–6 y: >10 mm healthy; <6 mm indicates moderate–severe malnutrition.

Waist & Hip Circumference / WHR

  • Waist: narrowest point between ribs & iliac crest; Hip: widest lateral point.

  • Risk thresholds (WHO):

    • Waist: >92 cm92\text{ cm} (M) / >80 cm80\text{ cm} (F) = increased risk.

    • Hip: >102 cm102\text{ cm} (M) / >88 cm88\text{ cm} (F) = substantially increased.

    • WHR: >0.900.90 (M) / >0.850.85 (F) = high metabolic risk.

Body Proportions

  • Upper-segment : Lower-segment ratio (US:LS)

    • Infant ↑ (trunk large); abnormal ↑ in achondroplasia, cretinism, short-limb dwarfism, sexual precocity, bowed legs.

    • Abnormally low ratio (long limbs) in Marfan (arachnodactyly), hypogonadism, Turner/Klinefelter syndromes, rickets, etc.

  • Arm Span

    • Distance fingertip–fingertip with arms outstretched.

    • <5 y: span 1–2 cm < height; 10–12 y: equal; adults: span ≈ height + 2 cm.

    • Excess span: Marfan, eunuchoidism, Klinefelter, coarctation of aorta.

    • Reduced span: short-limbed dwarfism, cretinism, achondroplasia.

Composite Indices & Classifications

Quetelet / Body Mass Index

BMI=mass (kg)height (m)2BMI = \frac{\text{mass (kg)}}{\text{height (m)}^2}

  • Adults (WHO):

    • <18.5 – underweight (16.0–16.99 moderate, <16 severe).

    • 18.5–24.99 – normal; Asian cut-off: 18.5–22.99.

    • 25–29.99 – pre-obese; 30–34.99 obese I; 35–39.99 obese II; ≥40 obese III.

  • Children: BMI-for-age >85th percentile = overweight; >95th percentile (+TSF >90th pct) = obesity.

Weight-for-Height Ratios & Power Indices

  • PI=Weight (g)Height (cm)2\text{PI} = \frac{\text{Weight (g)}}{\text{Height (cm)}^2}; a value <0.15 indicates PEM.

  • Wt/Ht %: <80 % under-nutrition; 80–120 normal; 120–130 over-nutrition; >130 obese.

Classical Pediatric Classifications

  • Gómez (Weight-for-Age vs. NCHS):

    • ≥90 % normal

    • 75–89.9 % Grade I

    • 60–74.9 % Grade II

    • <60 % Grade III

  • IAP (Harvard)

    • ≥80 % normal; 70–89.9 % I; 60–69.9 % II; 50–59.9 % III; <50 % IV.

  • Waterlow

    • Wasting: Height-for-Age normal, Weight-for-Height <−2 SD.

    • Stunting: Height-for-Age <−2 SD, Weight-for-Height normal.

    • Both: deficits in both indices.

  • SD Classification (WHO)

    • Normal: >Median−2 SD

    • Moderate: Median−3 SD to −2 SD (underweight, stunting, wasting per index)

    • Severe: <Median−3 SD.

Broka’s Index (Adults)

IBW (kg)=Height (cm)−100\text{IBW (kg)} = \text{Height (cm)} − 100

  • 10–20 % above IBW → mildly overweight; 20–30 % → overweight; 30–40 % → obese; >40 % severely obese.

  • 20–40 % below IBW → under/ severely underweight.

Body Composition & Interpretation

  • Weight change alone cannot differentiate fat vs. lean loss.

  • Combining MUAC, TSF, Mid-Arm Muscle Circumference (MAMC ≈ MUAC − π×TSF\pi \times TSF) yields lean mass estimate.

Ethical & Practical Notes

  • Non-invasive nature avoids harm; suitable for vulnerable populations.

  • Essential to calibrate equipment, standardise technique & train observers to minimise error.

  • Cut-offs must be contextualised: ethnic variation, local reference data vs. international standards.

Summary Cheat-Sheet (What to Remember)

  • Weight = acute; Height = chronic; combine for wasting vs. stunting.

  • MUAC <12.5 cm12.5\text{ cm} (1–5 y) = severe acute malnutrition (ready-to-use therapeutic food candidate).

  • BMI adult risk zones: 23 (Asian), 25 (global) start of overweight; 30 obesity.

  • Waist >102/88102/88 cm or WHR >0.90/0.850.90/0.85 → metabolic syndrome risk.

  • Normal pediatric milestones: weight ×2 @5 mo, ×3 @12 mo, length +25 cm first year.

  • Calibration, accurate age, consistent landmarks and multiple readings = reliable data.