Hi Charles, BMI (body mass index) was developed as a quick screening tool to determine body fat. Studies have shown a good correlation between BMI and direct measures of body fat, such as underwater weighing or skinfold thickness. BMI is intended to be used for screening and not diagnosing a health problem. If someone has a high BMI then other factors would be looked at to determine if weight was a health issue, such as frame size, muscularity, family history, skinfold measures, waist circumference, etc. All the best, Lisa Nelson, RD, LN Lose Weight - www.eNutritionServices.com