Body Mass Index (BMI) is a widely used screening tool that estimates healthy weight ranges based on the relationship between height and weight. Developed in the 1830s by Belgian mathematician Adolphe Quetelet, BMI is now used globally by healthcare providers to categorize weight status from underweight to obese. While BMI is a useful population-level screening tool, it has significant individual limitations — it doesn't distinguish muscle from fat, and the same BMI can have different health implications across different body types and ethnicities.