We suggest that a simple, rapid screening tool-the waist-to-height ratio (WHTR)-could help to overcome debates about the use of different body mass index (BMI) boundary values for assessing health risks in different populations. There are six reasons for our proposal: WHTR is more sensitive than BMI as an early warning of health risks. WHTR is cheaper and easier to measure and calculate than BMI. A boundary value of WHTR = 0.5 indicates increased risk for men and women. A boundary value of WHTR = 0.5 indicates increased risk for people in different ethnic groups. WHTR boundary values can be converted into a consumer-friendly chart. WHTR may allow the same boundary values for children and adults. Communicating messages about health risk could be much simpler if the same anthropometric index and the same public health message can be used throughout childhood, into adult life, and throughout the world. This simple message is: Keep your waist circumference to less than half your height.