It’s one of the most popular tools used in clinical practice and apparently schools are now sending letters home to parents if their child is tracking at a higher percentile (!) But is this a good tool?
For those unfamiliar with BMI, it is calculated by dividing your weight (kg) by the square of your height (m). The number given will then fall into a category - Underweight, Normal Weight, Overweight, Obese.
The limitations of this approach however are somewhat obvious, for example, we know muscle weighs more than fat, and therefore a sports person could be classified as overweight/obese according to this scale just due to their muscle/fat ratio. Also it doesn’t tell us the distributions of body fat, to assess whether it is therefore harmful to health.
The reason we started using this tool was to monitor trends in population over time, not actually as a measure of ‘health’ however it would appear that it is now being used to decide if people are he...