BMI

Body Mass Index divides weight in kilograms by height in metres squared, producing a screening number used across medicine.

Why it matters

BMI thresholds shape real decisions: bariatric surgery criteria commonly start at 35–40, medication eligibility often references it, and anaesthetic risk assessments consider it. It is useful precisely because it is simple.

Its limits

BMI cannot see muscle mass, fat distribution, pregnancy or age. Athletes measure “overweight” while carrying little fat. Treat it as a conversation starter with a clinician, never a diagnosis.