The data in the article could be used for a graphical display about obesity. The data might also stimulate questions such as: if one in five children is now overweight, and this is three times what it was 20 years ago, what proportion were overweight then? This is also a chance to discuss the meaning of percentage and its relationship to fractions and proportions.

KS3

Can pupils express the body mass index (BMI) calculation as an equation?

KS3-4

Consider a graph with height on the horizontal axis and weight on the vertical axis; what would a line of constant BMI look like on this graph? Can you produce a graph so that if someone plots their height and weight, they can see at a glance whether they are a healthy weight? This is a good graphical calculatorgraph plotter exercise. It should lead to profitable discussion of appropriate starting points and scales for the axes.