What is BMI?
Body Mass Index (BMI) is a numerical value calculated from your height and weight. The formula is: BMI = weight(kg) / height(m)². It was developed by Belgian mathematician Adolphe Quetelet in the 1830s as a population-level statistical tool — not as an individual diagnostic measure.
BMI Ranges and Categories
Below 18.5: Underweight. 18.5–24.9: Normal/Healthy weight. 25.0–29.9: Overweight. 30.0–34.9: Obese Class I. 35.0–39.9: Obese Class II. 40+: Obese Class III (Severe). The WHO uses these thresholds globally, though some countries (Japan, China) use lower cutoffs for Asian populations.
Limitations of BMI
BMI does not measure body fat percentage — it cannot distinguish between muscle mass and fat mass. A muscular athlete with low body fat may have an "overweight" BMI. It also does not account for fat distribution (visceral vs subcutaneous), age-related muscle loss, or ethnic differences in metabolic risk. Always consider BMI alongside waist circumference, blood work, and clinical assessment.
Better Health Indicators
Waist-to-Height Ratio (keep waist < half your height) is considered a better predictor of cardiovascular risk. DEXA scans measure actual body composition. VO₂ max reflects cardiovascular fitness. Use BMI as one data point, not a definitive measure of health.