BMI assumes you are the normal semi-sedentary modern person.
More importantly, BMI assumes you are of average height. Human weight doesn’t actually scale by the square root of height, so BMI has a systemic bias for tall people (too high) and for short people (too low).
As far as I recall, BMI was designed as a tool to compare whole populations (where the height bias averages out) and people who created it explicitly said that it’s not a good metric to evaluate individuals.
While it’s true that BMI is a rough metric and gets rougher when you’re dealing with unusual proportions or body compositions, those effects are often exaggerated. An athletic male of 6 feet 6 inches (99.8th percentile) and 210 pounds, which is about what you’d find in your average pro basketball player, would score as normal weight.
Too rough for my taste. Once your average pro basketball player adds 10 lbs of pure muscle and become 6′6″ at 220 lbs, BMI will declare him to be overweight.
More importantly, BMI assumes you are of average height. Human weight doesn’t actually scale by the square root of height, so BMI has a systemic bias for tall people (too high) and for short people (too low).
As far as I recall, BMI was designed as a tool to compare whole populations (where the height bias averages out) and people who created it explicitly said that it’s not a good metric to evaluate individuals.
While it’s true that BMI is a rough metric and gets rougher when you’re dealing with unusual proportions or body compositions, those effects are often exaggerated. An athletic male of 6 feet 6 inches (99.8th percentile) and 210 pounds, which is about what you’d find in your average pro basketball player, would score as normal weight.
Too rough for my taste. Once your average pro basketball player adds 10 lbs of pure muscle and become 6′6″ at 220 lbs, BMI will declare him to be overweight.