SECTION THREE
Body Mass Index (BMI)
Definition/RATION/ALE – what does it measure? (max 2 lines)
LBMI is an index of weight-for-height that is commonly used to classify underweight, overweight and obesity in adults, also called a Quetelet index. BMI is typically collected on non-pregnant women between 15 and 49 years of age, although the same cut-offs apply to any adult population group and as a result BMI can be collected on different groups of adults.
Methodology for collection – How to collect information for indicator (max 4 lines).
Measure the selected adults by taking their height (in cm) and weight (in grams). Pregnant women are typically excluded from data collection due to the distorting effect of pregnancy on a woman’s weight.
Methodology for analysis – How to analyse (Max 4 lines)
Visual demonstrations for thresholds
How to interpret: Urban v. rural, gender
- 1. Measurement readings are recorded in a database
- 2. BMI score of each measured individual is calculated by dividing the weight in kilograms by the square of the height in meters (kg/m2).
- 3. Measured individuals are divided into different categories based on their BMI score: proportion of people with a score of <18.5 are allocated to category 1 (underweight), proportion of people with a score from 18.6 and 24.9 are allocated to category 2 (normal weight), proportion of people with a score between 25 and 29.9 are allocated to category 3 (overweight) and proportion of people with a score of 30 or above are allocated to category 4 (obese).
- 4. For IPC purposes the prevalence of individuals with a BMI of <18.5 (underweight) is of primary interest: if prevalence is <5%, situation is indicative of Phase 1. Prevalence between 5 and 9.9% is indicative of Phase 2, prevalence between 10 and 19.9% is indicative of Phase 3, prevalence between 20 and 39.9% is indicative of Phase 4, and prevalence of 30% or more is indicative of Phase 5.
Notes on indicator –
What does the indicator not tell us.
How long is it reliable for?
- • BMI is impacted by both acute and chronic conditions and as a result the interpretation of the results may be difficult.
- • In areas affected by seasonality, the validity of MUAC is typically limited to the season in which the measurements were taken. In other contexts where there is no seasonal variation, BMI may be valid up to a year.
- • BMI does not distinguish between excess fat, muscle, or bone mass (i.e. individuals with the same BMI may have different levels of fat); it also does not provide any indication of the distribution of fat.
When to use it/when not to use it:
Appropriate for use in nutrition surveys in situations of varying severity. Informative indicator when data on nutritional situation of adults (rather than on that of only children) is required. In field conditions need to consider possible problems in acquiring and transportation of required measurement equipment for survey purposes.
IPC Categories:
2nd level outcome indicator
M&E: IMPACT, OUTCOME, OUTPUT, PROCESS
Impact/Outcome
