BMI
Body Mass Index
Body mass index, or BMI, compares your weight with your height. It is a screening measure, not a direct measurement of body fat, fitness or overall health.
What does a high or low BMI mean?
BMI can help identify when a closer assessment of weight and health may be useful. It cannot distinguish muscle from fat or show where fat is stored. Age, ancestry, waist size and other health measures change how it should be interpreted.
Adult screening categories, not an individual verdict
- Underweight category
- Below 18.5 kg/m²
- Healthy-weight category
- 18.5 to below 25 kg/m²
- Overweight category
- 25 to below 30 kg/m²
- Obesity category
- 30 kg/m² or more
These standard CDC categories apply to adults aged 20 and older. Children use age-specific charts, and pregnancy needs separate assessment. Health risks can occur at lower BMI in some populations, including people of Asian ancestry.
Sources: CDC
What can change this result?
What can raise it
- Weight gain over time, including when food intake exceeds energy needs.
- Gaining muscle, which BMI cannot distinguish from body fat.
- Fluid retention can increase weight without an increase in body fat.
What can bring it down
- Losing weight through sustainable changes in food intake and activity, if appropriate.
- Losing muscle can also lower BMI.
- Eating too little or losing weight because of illness.
Lower is not always better. Interpret BMI with your weight trend, waist measurement, strength and health; unexplained weight changes deserve attention.
What should I do next?
- Check that your height and weight were entered correctly.
- Consider waist size, blood pressure, blood tests, strength and nutrition alongside BMI.
- Discuss unexplained weight changes or concerns about eating with a clinician.
How this test works
BMI is weight in kilograms divided by height in meters squared. The same value can describe people with different body composition, so it is best used as a starting point for assessment.