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mjk1093 comments on Dunbar's Function - Less Wrong

27 Post author: Eliezer_Yudkowsky 31 December 2008 02:26AM

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Comment author: mjk1093 22 April 2016 04:54:15PM 0 points [-]

BMI assumes you are the normal semi-sedentary modern person. It's not meant to be used on serious athletes or weightlifters. For 95% plus of the population, BMI is a pretty accurate metric.

Comment author: Lumifer 22 April 2016 07:21:27PM 3 points [-]

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.

Comment author: Nornagest 22 April 2016 09:19:08PM *  0 points [-]

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.

Comment author: Lumifer 23 April 2016 12:06:42AM 1 point [-]

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.