DefinitionBMI is your weight in kilograms divided by your height in meters squared, a quick screen for whether weight may affect health.
What it means
In US units, BMI equals weight in pounds times 703, divided by height in inches squared. Adult categories:
- Under 18.5: underweight
- 18.5 to 24.9: healthy weight
- 25 to 29.9: overweight
- 30 or higher: obesity
BMI does not measure body fat directly. Muscular people can score high, and older adults can score normal while carrying more fat than it suggests. It works best as a starting point.
BMI matters a lot for GLP-1 eligibility. Wegovy and Zepbound labels cover adults with a BMI of 30 or more, or 27 or more with at least one weight-related condition.
For teens, BMI is read against age and sex growth charts as a percentile, not with the adult cutoffs. Wegovy is approved for some patients 12 and older based on those percentiles.
Why it matters
BMI is the number insurers and FDA labels use to decide who qualifies for weight-management drugs.