What does BMI actually tell you?

BMI estimates weight relative to height at a population level. It doesn't distinguish muscle from fat or account for fat distribution, so it misclassifies muscular people and can underestimate risk in South Asians, for whom lower cutoffs (overweight ≥23) are often used. Waist circumference adds useful information.

For South Asians, most guidelines use lower cutoffs: overweight from BMI 23 and obesity from 25, because cardiometabolic risk rises at a lower BMI than in European populations.

Waist circumference is often more informative — above 90 cm in men and 80 cm in women is the common South Asian threshold for increased risk.