What Is BMI?
The formula
BMI = weight (kg) / height (m)2. Clinics use bands (underweight, “normal,” overweight, obese) because the number is cheap and tracks risk in populations. It does not know if the kilos are muscle or fat. A stocky lifter and an inactive person can share a BMI and not share a health profile.
Use it as a flag, not a verdict
If BMI is high and waist is large and bloodwork is ugly, take it seriously. If BMI is high and you squat well, waist is reasonable, and labs are fine, you need a tape and a plan, not a panic. Body composition and waist or calipers beat BMI alone.
Do not chase a BMI class with crash dieting
Starving into “normal” while losing muscle is a bad trade. Lift, eat protein, lose fat slowly. Related: why body-fat percentage beats the scale.
Reviewed September 2026. Not medical advice.
