As I've mentioned in the past, my school district recently received a grant for programs to address the rate of childhood obesity in our schools. Therefore, I always take note of things like Explania's interactive, animated explanation of body mass index. The animation includes two interactive breaks during which viewers can calculate their body mass indexes and their ideal weights. The narrator uses metric units in the explanation, but the interactive elements can be used in metric or imperial units. Try it out as embedded below.
Calculate your Body Mass Index (BMI) - Explania
On a related note, you might also like Explania's explanation of cholesterol.
What is Cholesterol? - Explania