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wedrifid comments on Dunbar's Function - Less Wrong

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

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Comment author: wedrifid 07 June 2012 11:39:09AM 4 points [-]

BMI. Those things are fun. If I spend enough time in the gym I can get myself up to "Obese".

Comment author: [deleted] 07 June 2012 12:50:21PM 1 point [-]

Yeah, I weigh about the same as I did two years and a half ago, but I looked and felt much fatter back then. (OTOH none of the other people I mentioned in the grandparent exercise regularly, and anyway I only used the BMI because it was the quickest quantitative measure I could think of.)

Comment author: [deleted] 07 June 2012 02:27:50PM 0 points [-]

Oh, I should clarify that my arguments were not meant to chastise you for using BMI. I don't have any problem with it in the way you use it; it looks like it falls under argument two but it's clear that you're using it as a rough signal of degrees of morbid obesity.

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.