What BMI measures
BMI compares weight with height to create a simple screening number. It can be useful for population-level trends, but it does not directly measure body fat, fitness, or health.
Where BMI falls short
BMI does not distinguish between muscle and fat, and it does not show where body fat is carried. That means athletes, older adults, and people with different body compositions can receive misleading categories.
How to use it sensibly
Treat BMI as a starting point, not a diagnosis. Waist measurement, blood pressure, blood tests, fitness, and medical history all provide important context.