Body Mass Index
A quick, evidence-based estimate of weight-related health risk — curated by clinicians.
What is BMI?
Body Mass Index is the metric currently used to characterize anthropometric weight relative to height. It estimates body fat and categorizes weight status, and it is a powerful health risk signal — high BMI correlates with , systemic inflammation, metabolic dysfunction and mortality.
Limitations
BMI does not differentiate between body lean mass and body fat mass. For populations with or for , a BMI value alone can be misleading. Use BMI as a starting point, not a verdict.
FAQ
No. The clinical interpretation of BMI must be adapted to specific populations. Ethnicity, age, sex and body composition all shift how BMI maps to actual health risk.
Adult thresholds do not apply. The CDC and WHO classify pediatric weight status using age- and sex-specific BMI percentiles plotted on standardized growth charts.
| Percentile | Category |
|---|---|
| < 5th | Underweight |
| 5th–84th | Normal weight |
| 85th–94th | Overweight |
| ≥ 95th | Obesity |
BMI provides a useful initial estimate of weight-related health risk in adults, but the relationship between BMI and mortality differs across age groups.
Low BMI in older adults is strongly linked to , , and increased mortality. Functional status and muscle mass should be prioritized — not BMI alone.
No. In athletes and individuals with high lean body mass, BMI may overestimate adiposity because increased muscle mass raises total body weight.
Recommended assessments:
- Body composition analysis
- Waist circumference
- Performance and metabolic markers
Only pre-pregnancy or in very early pregnancy. During pregnancy, BMI becomes unreliable because weight changes reflect fetal growth and physiological adaptations rather than the individual's adiposity.
- Wellens RI, Roche AF, Khamis HJ, Jackson AS, Pollock ML, Siervogel RM. Relationships between the body mass index and body composition. Obes Res. 1996;4(1):35–44.
- Bramante CT, Palzer EF, Rudser KD, Ryder JR. BMI metrics and their association with adiposity, cardiometabolic risk factors, and biomarkers in children and adolescents. Int J Obes.
- Curr Obes Rep. 2015 September;4(3):379–388. doi:10.1007/s13679-015-0161-z.
- Wellens RI, Roche AF, Khamis HJ, Jackson AS, Pollock ML, Siervogel RM. Relationships Between the Body Mass Index and Body Composition. Obes Res. 1996;4:35–44.
- Nuttall FQ. Body Mass Index. Obesity, BMI, and Health: A Critical Review. Nutrition Today.
- Zahid S, Peng AW, Razavi AC, Yao Z, Blumenthal RS, Blaha MJ. Center Stage: Putting Obesity Staging Systems Into the Spotlight. Prev Chronic Dis. 2025;22:250222.
- Milanese C, Itani L, Cavedon V, Saadeddine D, Raggi S, Berri E, El Ghoch M. Revising BMI Cut-Off Points for Overweight and Obesity in Male Athletes. Nutrients. 2025;17:908.
BMI is a screening tool, not a diagnostic test. Talk to your clinician for a personalized assessment.