The measure for determining a person's weight category is called the Body Mass Index. Doctors and physical trainers use a standard BMI chart to label a person as underweight, normal weight, overweight, or obese. The BMI is a simple comparison of a person's metric height and weight. The purpose is to gain a basic measurement of body fat based on the two characteristics. A BMI under 18.5, "underweight," tells doctors that someone has very little body fat or muscle. The "normal weight" category represents a BMI of 18.5 to 24.9. Overweight persons have a BMI of 25 to 29.9. And "obesity" is the category for persons with a BMI of 30 or greater. Persons falling in the obese category are at higher risk of diseases that may occur with more body fat
. High BMI levels increase a person's risk for heart disease, problems related to high blood pressure, type 2 diabetes, respiratory problems, and even certain cancers. On the other hand, the BMI is very simple and is criticized for overestimating body fat in athletes. For example, a body builder or athlete is going to weight a lot more than a sales associate or a professor who is the same height. The BMI might label this athlete as obese even though he or she is perfectly healthy and probably in better shape than the other person. Conversely, BMI calculations may give the impression that an elderly person, who has lost a lot of muscle mass, has less body fat
Before implementing teaching strategies for introducing the Body Mass Index to elementary students, teachers must have a serious discussion about obesity to prevent any teasing, mocking, or embarrassment of students who may be unhappy with their body mass index. Students should keep their height and weight measurements to themselves to avoid unhealthy competition.