What Is BMI?
Body Mass Index (BMI) is a simple formula that converts a person's weight relative to height into a single numerical value. Developed by Adolphe Quetelet in the 19th century, it is now one of the most common screening metrics worldwide.
BMI is not a diagnosis by itself. Health professionals use it as a first screening filter because it is fast, low-cost, and broadly useful across populations.
Example: for a person weighing 70 kg and measuring 1.75 m, the calculation is:
70 / (1.75 × 1.75) = 22.9, which falls in the normal range.
Weight Categories
The World Health Organization (WHO) uses the following categories for adults:
For children and adolescents, age- and sex-adjusted percentile charts should be used; adult thresholds are not valid for this group.
When Is BMI Meaningful?
BMI is strong as a rapid triage metric in large population screening. Across big datasets, it correlates with cardiovascular risk, type 2 diabetes, and hypertension.
For individual assessment, BMI alone is not enough. Clinicians usually combine it with waist circumference, blood work, and clinical evaluation.
Keep this in mind: BMI is an alert system, not a diagnosis. Even when thresholds are exceeded, results should be reviewed with a healthcare professional.