Definition and Calculation
BMI (Body Mass Index) is calculated by dividing weight in kilograms by height in meters squared. Devised in 1832 by Belgian statistician Adolphe Quetelet, the formula is BMI = weight / (height x height). For someone 170 cm tall weighing 65 kg, the result is 65 / (1.70 x 1.70) = 22.5. It is widely used as a simple screening tool for population-level obesity.
WHO vs. Asian Classification Standards
The WHO international standard defines BMI 25+ as overweight and 30+ as obese. However, the Asia-Pacific region, including Japan, adopts stricter thresholds of 23+ for overweight and 25+ for obese, because body fat percentage tends to be higher at the same BMI compared to Western populations.
This difference in standards can cause confusion in international comparisons, as the same BMI value may be classified as "normal" in one region and "overweight" in another.
Limitations - The Muscle Mass Problem
Since BMI uses only weight and height, it cannot distinguish muscle from fat. Athletes and fitness enthusiasts may have high BMI due to muscle mass with low health risk. Conversely, "skinny fat" individuals with normal weight but high body fat percentage go undetected by BMI alone.
Use in MyRank
MyRank displays your BMI as a relative position among 8 billion people worldwide. Knowing where you stand in the global distribution can motivate health management. However, BMI is just one indicator and should be combined with body fat percentage, waist circumference, and blood test results for a comprehensive health assessment.