Body measurements can screen, classify, and track nutrition status across ages when applied with standard methods.
Low Risk
Needs Review
High Risk
Rapid Screening (MUAC)
- Find left arm midpoint
- Wrap tape without squeeze
- Read once more to confirm
Outreach
Standard Growth Check
- Weight + length/height
- Compute WHZ/BMI
- Classify on charts
Clinic
Clinic Workup
- Add waist, diet recall
- Screen for illness
- Set return date
Follow-Up
What This Approach Does And When To Use It
Anthropometry is the toolkit for sizing up nutrition through simple body measures that reflect tissue gain or loss. Weight, length or height, mid-upper arm circumference, and visible oedema give a fast read on short-term change and long-term growth. The same tools guide clinical triage, program screening, and surveys.
Growth faltering, wasting, or overweight carry health risks. Routine measurement lets teams spot issues early and track response after care. WHO growth standards and CDC adult categories provide the reference points used worldwide.
Core Measures You’ll Record (Table)
| Measure | What It Captures | Notes & Typical Cutoffs |
|---|---|---|
| Weight-for-height/length (WHZ/WLZ) | Acute thinness or wasting | Low if z < −2; very low if z < −3 |
| Height-for-age (HAZ) | Chronic growth faltering | Low if z < −2 |
| Weight-for-age (WAZ) | Composite underweight | Sensitive, not for admission alone |
| Body mass index (BMI) | Weight relative to height | Adults: under 18.5 underweight; 25–29.9 overweight; 30+ obesity |
| Mid-upper arm circumference (MUAC) | Muscle/fat reserve | Child severe: <115 mm with or without oedema |
| Bilateral pitting oedema | Protein-energy imbalance | Any grade implies severe disease in young children |
Anthropometry For Nutrition Status Checks: Methods
Use calibrated gear on a flat, private spot. Explain the steps and ask for assent or consent. Remove shoes, hats, and bulky items. Record age and sex; both matter for charts.
Weight
Zero the scale. For infants, use a tared sling or infant scale. For small children who can’t stand still, weigh the caregiver, then both together, and compute the difference. Read to the nearest 0.1 kg when the dial or display settles. Repeat once; if the readings differ, take a third and keep the two closest.
Length Or Height
Children under two years: measure recumbent length. Older children and adults: measure standing height. For recumbent length, keep the head midline at the board’s fixed end, legs straight, feet at right angles, and slide the foot piece snug. For standing height, heels together, back straight, eyes level, and the headboard lowered to touch the crown. Read to 0.1 cm.
Mid-Upper Arm Circumference (MUAC)
Find the left arm midpoint between acromion and olecranon. Wrap the tape gently at that point, snug but not compressing. Read at eye level. Repeat and record the average. If you see swelling on both feet, classify oedema before relying on MUAC.
Oedema Check
Press both thumbs on the tops of both feet for three seconds, then lift. A clear pit on both sides classifies bilateral pitting oedema. Presence is what counts in young children.
From Numbers To Classifications
For children under five, compute z-scores using WHO charts or software. WHZ/WLZ below −2 means wasting; below −3 means severe wasting. HAZ below −2 signals stunting. MUAC below 115 mm in a child 6–59 months also marks severe status. Oedema alone places a child in the severe group. You can cross-check the wording for wasting in the WHO note on terminology.
For ages 5–19, use age- and sex-specific BMI-for-age percentiles or z-scores. For adults, compute BMI with weight in kilograms divided by height in meters squared, then classify: under 18.5, 18.5–24.9, 25–29.9, and 30 or above. A quick refresher on these ranges sits on the CDC page for adult BMI categories.
Data Quality: How To Reduce Error
Work in pairs when possible: one measures, one records. Check scale zero before each person. Keep tapes straight and at the correct landmark. Re-check any value that drifts far from the rest of the group. Train with a standardization session where each staff member measures the same people and results are compared. Document make and model of each device.
Common pitfalls include heavy clothing, bent knees during length, twisted tapes for MUAC, and mis-read digits. Field forms should include space for repeats and comments so odd values are easy to spot later.
Interpreting Results In Context
Numbers tell only part of the story. Ask about recent illness, appetite, diet quality, feeding changes, disability, pregnancy, and medicines. Acute infection can drop appetite and shift fluids. Seasonal food gaps can pull down MUAC and weight quickly. Note these details so a repeat visit can judge trend, not just a single point.
For programs, keep the same methods over time. Switching from length to height or from one MUAC tape pattern to another can create apparent changes that are only method shifts. Record the method on each line of data.
When Each Indicator Works Best
WHZ/WLZ: sharp changes in tissue over weeks; sensitive to hydration and scale error.
HAZ: long-term growth pattern; slow to shift and not for rapid triage.
WAZ: helpful for population tracking and clinic flags; not an admission criterion by itself.
MUAC: simple, fast, and predictive for mortality risk in young children; great for outreach.
BMI: a broad look at body size in adults; combine with waist, blood pressure, and labs when available.
Reference Ranges And Admission Rules (Table)
| Group | Indicator | Thresholds |
|---|---|---|
| Children 6–59 mo | WHZ/WLZ | < −2 wasting; < −3 severe |
| Children 6–59 mo | MUAC | < 115 mm severe; 115–124 mm moderate |
| Children 6–59 mo | Oedema | Any bilateral pit → severe |
| Ages 5–19 | BMI-for-age | Use z-scores/percentiles on charts |
| Adults 20+ | BMI (kg/m²) | < 18.5 underweight; 18.5–24.9 healthy; 25–29.9 overweight; ≥ 30 obesity |
| Adults, MUAC | Field screening | Program-specific cutoffs; note local policy |
Practical Workflow You Can Follow
1) Prepare
Calibrate scales with a known weight. Check tapes against a ruler. Clean and dry boards. Set up a private space with good light. Print age-sex tables or load the app you plan to use.
2) Measure
Record age, sex, and date first. Take weight, length or height, MUAC, and oedema in the same order each time. Repeat any reading that feels off. Mark the form with the method used and any aids such as a sling.
3) Classify
Convert to z-scores or BMI. Classify per reference bands. If bilateral pitting appears, treat as severe even if MUAC or WHZ look borderline. Note any red flags like persistent weight loss or feeding problems.
4) Act
For severe states, follow local referral rules now. For moderate states, give counseling, a plan, and a return date. Document what you advised so the next visit can check adherence and barriers.
Ethics, Dignity, And Data Protection
Measure in a respectful, private way. Ask before you touch. Share results in clear terms and avoid blame. On shared devices or forms, de-identify data where possible. Only collect what the service needs.
Tools And References You’ll See In Practice
WHO growth standards define wasting and stunting for young children across countries. CDC pages explain BMI use and how adult bands are interpreted in clinics. MUAC tapes from UNICEF are color-coded and designed for quick outreach work.
Smart Tips That Save Time
- Weigh at the same time of day during follow-ups to reduce fluid swings.
- Ask about recent diarrhea, fever, or antibiotics when a sharp drop appears.
- Use the same arm for MUAC each visit.
- Keep spare batteries for digital scales.
- Write units next to every number; it prevents mix-ups later.
What To Tell Clients And Caregivers
Explain that these measurements are a screening step, not a diagnosis. Share where the value falls on the chart and what the next step will be. Encourage a return visit, even if the value sits near the healthy band, when feeding has changed or illness lingers.
Limits And When To Add More Tests
BMI can misclassify muscular adults. Edema can hide weight loss. Acute dehydration can make a thin child look worse on the day. Add waist, skinfolds, or bioimpedance only when trained and when it changes care. A skilled clinical exam and a short diet history add context fast.
Program Reporting And Survey Use
For clinics, track the share of clients in each band and the rate of return after counseling. For surveys, report prevalence of wasting, stunting, underweight, and overweight with 95% confidence intervals and the exact reference used. Always state the age bands, sampling frame, and any exclusions.