Researchers estimate that by 2015 almost 75 percent of American adults will be obese. But how do they determine whether a body is underweight, healthy, overweight, or obese?

In this lesson we’ll explore the body mass index, or BMI, which uses height and weight measurements to help determine whether a person is at a “healthy” weight. We’ll use this formula to find out the weight statuses of celebrities, from Taylor Swift to Arnold Schwarzenegger, and discuss whether BMI is all it’s cracked up to be.

### Students will

• Evaluate the BMI formula and classify scores for different values of height and weight
• Given a person with an “unhealthy” BMI, determine necessary weight loss or gain to reach “healthy” status
• Describe qualitatively how changes in height and weight interact to produce changes in BMI
• Compare BMI scores and apparent body composition for various pairs of people
• Discuss effectiveness of BMI as a means of classifying “healthy” weight

### Before you begin

Students should know there are twelve inches in a foot. In order to calculate the weight change necessary for a person to go from an unhealthy category to the “healthy” one, students will have to be able to solve equations in one variable of the form 18 = 2x / 32.

Note: Approximately 1 in 3 American children are overweight or obese, while many others struggle with eating disorders. Before beginning the lesson, you might remind students that this is a sensitive topic for many people, and that you expect their behavior to demonstrate understanding and empathy.