# Reasons why the BMI is useless **URL:** \ **Category:** In My Humble Opinion\ **Tags:** diet-weight-loss\ **Created:** [September 15, 2024, 5:28pm UTC](https://boards.straightdope.com/t/reasons-why-the-bmi-is-useless/1007307 "2024-09-15T17:28:05Z")\ **Posts on this page:** 6\ **Page:** 5
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [September 16, 2024, 8:42pm UTC](https://boards.straightdope.com/t/reasons-why-the-bmi-is-useless/1007307/81 "2024-09-16T20:42:31Z")
> [@DSeid](#): > > Yes. And statistically at significantly increased risk for a variety of conditions. Which at an individual level- is meaningless. > [@cormac262](#): > > . I believe that the calculation was based on actual measurements, but that the sample only included people within a certain height range. 17th century euro peasants were not known for their height. Yes, they had to add several rows for taller people. > [@Sage\_Rat](#): > > If it’s the healthiest weight then, by definition, it’s not emaciated It could be the healthiest weight for most of the population. That does not come over to being the healthiest weight for any given individual. > [@Sage\_Rat](#): > > Don’t eat anything with added sugars or that’s deep fried and you’re liable to see notable changes, IMHO the low carb high protein diets works _mostly_ due to the fact that they pretty much cut out all snack food other than beef jerky and celery sticks. One of my friends decided she was gluten intolerant (she _was_ diabetic) so she cut all the stuff out- and she felt better. Surprise surprise- cutting out cookies and donuts and cake does make pretty much anyone feel better- especially if you are diabetic. ---
**Author:** ![Zyada](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zyada/32/3028_2.png) [@Zyada](https://boards.straightdope.com/u/Zyada)\ **Post date:** [September 16, 2024, 11:54pm UTC](https://boards.straightdope.com/t/reasons-why-the-bmi-is-useless/1007307/82 "2024-09-16T23:54:35Z")
> [@DrDeth](#): > > 17th century euro peasants were not known for their height. Yes, they had to add several rows for taller people. Repeating: published in 1835, probably middle class Belgians ---
**Author:** ![Zyada](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zyada/32/3028_2.png) [@Zyada](https://boards.straightdope.com/u/Zyada)\ **Post date:** [September 16, 2024, 11:58pm UTC](https://boards.straightdope.com/t/reasons-why-the-bmi-is-useless/1007307/83 "2024-09-16T23:58:40Z")
> [@DrDeth](#): > > One of my friends decided she was gluten intolerant (she _was_ diabetic) so she cut all the stuff out- and she felt better. Surprise surprise- cutting out cookies and donuts and cake does make pretty much anyone feel better And if you’re cutting out the chips as well, that’s a lot of salt you cut out. One reason why most diets can advertise “lose 10 pounds the first week!” is because people drop water weight when they switch from to controlling what they eat. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [September 17, 2024, 12:02am UTC](https://boards.straightdope.com/t/reasons-why-the-bmi-is-useless/1007307/84 "2024-09-17T00:02:38Z")
> [@DrDeth](#): > > Which at an individual level- is meaningless. Certainly not me, both as an individual hoping for a long healthspan, or as a provider. I don’t get much excited over an election model changing by 6% probability, but a health forecast model changing by 25, 50% … that I think is worth noting! ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [September 17, 2024, 12:04am UTC](https://boards.straightdope.com/t/reasons-why-the-bmi-is-useless/1007307/85 "2024-09-17T00:04:42Z")
> [@cormac262](#): > > My point is that for me to lose **that much weight** (over 25% of my current weight) would require either “depleting” myself to the point of being emaciated or lopping off a limb. Obviously I can’t speak to your particular health situation, but 130 lbs for a 5’1" person is not emaciated. It’s arguably on the chubby side (depending on muscle mass). BMI is inaccurate for the short and tall–but it exaggerates _thinness_ on the low end (Shaq, etc. have the opposite problem). They should probably target a slightly _lower_ BMI than the normal charts. ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [September 17, 2024, 4:03am UTC](https://boards.straightdope.com/t/reasons-why-the-bmi-is-useless/1007307/86 "2024-09-17T04:03:29Z")
> [@DrDeth](#): > > It could be the healthiest weight for most of the population. That does not come over to being the healthiest weight for any given individual. In theory, yes. But, let’s say that I have yearly numbers for a reasonably large sample of people, going back decades. I can look at the oldest living survivors and see if any of them were heavier than they should have been and if any were lighter. Minus a theory for why one might be higher and another lower, that doesn’t really tell me anything. Given samples of millions, and sufficiently detailed information about what food they were eating, their usual macro breakdown, what supplements they were taking, how often they exercised, how clean the air was that they breathed, how much sun they got, etc. maybe you might be able to correct for all the confounding elements and narrow in on a few genes or physical attributes (e.g. thick bones). I don’t believe we’re anywhere near being able to do that. Someone might be able to move faster by tightly controlling the genetics and life style of animals like mice and rats, but I don’t believe anyone has done that. I can imagine some scenarios where we might theorize some difference (thick bones) but a) that’s an imagined thought not a scientific reality at this moment in time, and b) nothing I can think of from the various theories of aging feel like they would vary much from person to person with a primary emphasis on body weight. For example, stress tends to cause aging to occur faster. So we might hypothesize, for example, that Samoans with the obesity CREBRF gene variant would be under more stress at lower body weights. Except, hunger seems to mostly revolve around an extreme discomfort towards loss. The most likely explanation for the Samoan case is that, as an island people, they more strongly selected for more extreme reactions to hunger not so much a desire for fat. 19th century drawings of them, for example, do not depict overweight people: > **[Native Samoans - Scanned 1890 Engraving](https://www.istockphoto.com/vector/native-samoans-gm1143767742-307281189)** > > Native Samoans - Scanned 1890 Engraving In all of the planet, there’s no humans who were obese until modern production powers came into being. So we might believe that going up and down in weight is more onerous and stressful for Samoans than others, but we have no reason to think that they’re going to be stressed for their entire lives if they live at a pre-modernity body weight. What would have been the point of nature evolving them to be stressed out until they come to live in an artificial, industrial environment that evolution has no reason to expect nor ability to target? If everyone, through all of history was a slender reed with a thin layer of crazy dense muscle underneath, and that’s all nature really allowed until the last century or two, there’s no reason to think that we’d be adapted for any other body shape. The best that I can realistically imagine is that one might have some very specific illness that demands a certain level of adiposity to delay death. That’s not the situation of nearly anyone and, for the one of two for whom it might be, the bad BMI is probably still hurting you, just _less_ than the other thing. Anyone making the assumption that they’re that person - minus a doctor’s order - is best to go back to the drawing board. [Previous page](https://boards.straightdope.com/t/reasons-why-the-bmi-is-useless/1007307.md?page=4)