Understanding BMI
BMI was designed as a population screening tool, not a personal diagnosis. It's fast and free, which is why doctors still use it as a first check. But it can misclassify people with above-average muscle mass, older adults, and some ethnic groups.
When BMI is useful
- Tracking weight change over time for the same person.
- Estimating population-level health risk.
- Setting a rough initial weight goal.
When to ignore BMI
- If you strength train regularly and carry significant muscle.
- If you're pregnant or recently postpartum.
- If you're over 65 and research suggests a slightly higher range may be protective.