body mass index
Enable an agent to recognise, calculate, interpret and qualify body mass index as a mass-to-height index without treating it as a direct measurement of body fat or a standalone diagnosis.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
recalled by Codex without web access - no source was read
Researched by: Codex
Purpose and description
Enable an agent to recognise, calculate, interpret and qualify body mass index as a mass-to-height index without treating it as a direct measurement of body fat or a standalone diagnosis.
Body mass index (BMI) is an anthropometric index calculated as a person's mass in kilograms divided by the square of their height in metres, used to classify weight relative to height and as an indirect screening measure of weight-related health risk.
It can be Calculate BMI from compatible mass and height observations while preserving the original inputs.; Check units, input pairing, calculation arithmetic and reported precision.; Assign a category or reference-relative position only after checking the selected framework's applicability.; Compare repeated observations and identify changes in measurement method or reference framework.; Explain what a BMI result supports and identify additional evidence needed for a proposed decision..
Distinguishing features
A BMI observation must be reproducible from body mass divided by squared height after appropriate unit conversion.
BMI has conventional units of kg/m²; a mass value alone or a mass-to-height ratio without squaring height is not BMI.
A BMI value is distinct from a category assigned to it: the category additionally requires a named interpretation framework.
BMI-for-age percentiles and z-scores require a reference distribution and are not interchangeable with the underlying BMI value.
BMI does not distinguish fat mass from lean mass; body-fat percentage cannot be read directly from the index.
Scope
+ The definition of BMI as body mass in kilograms divided by height in metres squared
+ Mass and height observations, measurement conditions and calculation provenance
+ BMI values, units, precision and changes across comparable observations
+ Classification and standardisation under explicitly identified population and age reference frameworks
+ Applicability limits and the evidence needed before acting on a BMI result
- Body mass and stature as independently modelled physical quantities
- Direct measurements and estimates of body composition
- Obesity, malnutrition and other clinical conditions as diagnoses
- Complete assessments of cardiometabolic health or individual disease risk
- Dietary, medication, exercise and surgical treatment plans
- Alternative anthropometric indices such as waist-to-height ratio
Characteristics
- BMI value
- kg/m² Records the derived quantity independently of classifications or clinical conclusions.
- Input body mass
- kg, with original value and unit retained Makes the calculation reproducible and exposes conversion or measurement errors.
- Input height or length
- m, with original value, unit and measurement method retained Height is squared in the denominator, and different measurement methods may affect comparability.
- Observation pairing
- Links to the subject and dated mass and height observations Prevents combining measurements from different subjects or incompatible time points.
- Input provenance
- Measured, self-reported, estimated or unknown, recorded separately for each input Identifies the evidential basis of the result.
- Calculation quality
- Unchecked, verified, flagged or not calculable, with reasons Separates an available number from a reproducible and usable observation.
- Interpretation framework
- Named authority, reference publication, version and applicability criteria Makes category assignments traceable to a particular convention.
- BMI category
- Framework-defined label, unclassified or not applicable Prevents treating framework-dependent labels as intrinsic properties of the number.
- BMI-for-age position
- Percentile or z-score with named reference and required demographic inputs Keeps reference-relative interpretation distinct from raw BMI.
- Interpretive applicability
- Supported, qualified, unsupported or unresolved for the stated use Allows an agent to retain a calculated result while restricting conclusions drawn from it.
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 5 bundles · 9 layers · 17 findings · 29 questions.
Index definition Establishes what counts as BMI and separates the quantity from related measures and interpretations.
An agent must recognise the index before calculating it or accepting an imported result.
Formula and units
Defines the mathematical operation and its unit conventions.
Mass over squared height
BMI is calculated as mass in kilograms divided by height in metres squared.
- Does the supplied value use mass divided by squared height? definition
- What original units and conversion factors were used before calculating kg/m²? measurement
Quantity boundaries
Distinguishes BMI from body composition, classifications and diagnoses.
Index versus inference
The calculated index, its assigned category and any health inference must remain distinguishable.
- Is this record a raw BMI value, a BMI category, a percentile or a clinical conclusion? definition
- Does any proposed interpretation incorrectly equate BMI with body-fat percentage or a diagnosis? boundary
Measurement and calculation Connects each BMI result to identifiable inputs and reproducible arithmetic.
Correct arithmetic cannot compensate for incompatible, undocumented or incorrectly converted inputs.
Input observations
Records where mass and height came from and whether they can be paired.
Compatible mass and height pair
A BMI observation needs mass and height linked to the same subject, with dates and measurement methods available for review.
- Were mass and height measured, reported or estimated, and on what dates? provenance
- Was standing height, recumbent length or an estimated stature used, and is that input suitable for the intended interpretation? measurement
- Are the subject identity and time separation of the two inputs acceptable for this observation? boundary
Derived value quality
Checks reproducibility, precision and consequences of uncertain inputs.
Reproducible BMI result
Retain sufficient input precision to reproduce the result and distinguish calculation errors from uncertainty in measurement.
- Can the reported BMI be reproduced from the retained inputs before display rounding? measurement
- Could input uncertainty or rounding move the result across a boundary in the selected classification framework? measurement
Reference-based interpretation Models the rules that turn a BMI value into a category or reference-relative position.
BMI classifications depend on a reference framework whose population, purpose and version must be explicit.
Classification framework
Identifies category definitions and the population to which they apply.
Traceable category assignment
A category assignment must identify its authority, cutoffs, boundary rules and intended population.
- Which source and version define the category labels, cutoffs and inclusion of boundary values? provenance
- What age, population and use criteria determine whether this classification applies? boundary
- Does the framework distinguish descriptive categories from thresholds that trigger further assessment? action
Age-relative interpretation
Handles BMI interpretation that depends on a growth reference.
Reference-relative position
A BMI-for-age percentile or z-score is a separate derived result requiring a named reference and its prescribed inputs.
- Which growth reference, age precision and sex variable does this calculation require? measurement
- Is the subject within the reference's supported age range, and how are transitions between frameworks handled? boundary
Applicability and decisions Governs how an agent uses BMI in individual assessment, repeated observations and population summaries.
A valid BMI calculation may still be insufficient for the conclusion or action being proposed.
Individual interpretation limits
Records circumstances and missing evidence that qualify interpretation.
Context-qualified use
Assess whether factors such as pregnancy, fluid accumulation, limb loss or unusually high muscularity require qualification under the chosen guidance.
- Which documented circumstances affect the suitability of this BMI interpretation? boundary
- What additional anthropometric or clinical evidence is needed before making the proposed individual decision? action
- Which source supports qualifying or withholding interpretation in this circumstance? provenance
Comparison and aggregation
Checks whether longitudinal and population comparisons preserve compatible meanings.
Comparable BMI observations
Interpret changes and summaries alongside measurement methods, reference choices and population composition.
- Could an apparent change reflect different input methods, growth or a change of classification framework? measurement
- Do population comparisons use compatible age ranges, measurement sources and category definitions? boundary
- Does the proposed conclusion stay within what these BMI observations establish? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Check these first
Recalled without web access and unsourced; every item is a lead to verify.
- This is recall-based information; no sources were consulted.
- Verify the applicable jurisdiction, population, age range and guideline edition before applying classification or treatment thresholds.
- BMI-for-age percentiles and z-scores require a named growth reference; results and category boundaries are not interchangeable across references.
- Which of these check these first hold for the sense of body mass index this model covers, and on what evidence? provenance
Kinds and varieties
Recalled without web access and unsourced; every item is a lead to verify.
- Adult BMI interpreted using fixed cutoffs
- Child and adolescent BMI interpreted relative to age and sex using growth references
- Which of these kinds and varieties hold for the sense of body mass index this model covers, and on what evidence? provenance
Identifiers and schemes
Recalled without web access and unsourced; every item is a lead to verify.
- LOINC - 39156-5 - Observation code for body mass index (BMI) [Ratio].
- UCUM - kg/m2 - Unit expression for BMI; identifies the measurement unit, not the concept itself.
- Which of these identifiers and schemes hold for the sense of body mass index this model covers, and on what evidence? provenance
Standards and regulation
Recalled without web access and unsourced; every item is a lead to verify.
- World Health Organization adult BMI classification: underweight below 18.5 kg/m², normal range 18.5 to below 25, overweight at least 25, and obesity at least 30.
- World Health Organization Child Growth Standards and growth reference for ages 5-19 provide BMI-for-age interpretation.
- US Centers for Disease Control and Prevention growth charts provide age- and sex-specific BMI interpretation for children and adolescents.
- Which of these standards and regulation hold for the sense of body mass index this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Screening adults for weight categories that may warrant further assessment.
- Monitoring children's growth using BMI-for-age references.
- Estimating population prevalence and trends in underweight, overweight and obesity.
- Defining eligibility or stratification criteria in clinical studies and some treatment pathways.
- Following changes in weight relative to height over time.
- Which of these real-world use hold for the sense of body mass index this model covers, and on what evidence? provenance
Typical measurements
Recalled without web access and unsourced; every item is a lead to verify.
- Body mass index - No universal healthy range; the conventional WHO adult normal category is 18.5 to below 25. - kg/m²
- BMI-for-age percentile - Expressed on a 0-100 percentile scale relative to a specified age- and sex-specific reference. - percentile
- BMI-for-age z-score - Reference-dependent; zero corresponds to the reference median. - dimensionless
- Which of these typical measurements hold for the sense of body mass index this model covers, and on what evidence? provenance
Failure modes and hazards
Recalled without web access and unsourced; every item is a lead to verify.
- BMI does not distinguish fat mass from muscle, bone or other components of body mass.
- BMI does not describe fat distribution and can miss elevated risk associated with abdominal adiposity.
- Age, sex, ancestry and body composition affect the relationship between BMI, adiposity and health risk.
- Pregnancy, fluid retention, limb loss and inaccurate height or weight measurements can make standard interpretation misleading.
- Treating a BMI category as a complete individual diagnosis can cause inappropriate reassurance, treatment decisions or stigma.
- Which of these failure modes and hazards hold for the sense of body mass index this model covers, and on what evidence? provenance
Regional variation
Recalled without web access and unsourced; every item is a lead to verify.
- Some Asian national and clinical guidelines use lower BMI thresholds for risk assessment or intervention because metabolic risk may occur at lower BMI.
- Paediatric classifications differ between WHO references, CDC charts and other national or international reference systems.
- Which of these regional variation hold for the sense of body mass index this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Recalled without web access and unsourced; every item is a lead to verify.
- Body mass - Body mass measures mass alone; BMI divides mass by squared height.
- Body fat percentage - Body fat percentage estimates the fraction of mass that is fat; BMI cannot identify that fraction.
- Waist circumference - Waist circumference measures abdominal size; BMI combines total mass and height.
- Obesity - Obesity concerns excess adiposity and its health implications; BMI is an indirect index commonly used in its classification.
- Ponderal index - Ponderal index divides mass by cubed height rather than squared height.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of body mass index this model covers, and on what evidence? provenance
What the second pass must settle
- Which authoritative adult and growth-reference frameworks should the publication support, and how should it represent disagreements between their intended uses and thresholds?
- What evidence and guidance should govern population-specific interpretation without treating broad demographic categories as precise descriptions of individuals?
- Which circumstances require qualified interpretation, an alternative measure or withholding classification, and which sources establish those distinctions?
- What input-age, measurement-method and uncertainty rules are defensible for deciding whether a mass and height pair supports the intended use?
- Does an existing Vercy world model already own BMI or an encompassing anthropometric concept to which this registry entry should link?