5 ms·

It is bizarre that you would read an article which says, “using body-mass index (BMI) to measure obesity is likely the most problematic factor,” and then immedi

It is bizarre that you would read an article which says, “using body-mass index (BMI) to measure obesity is likely the most problematic factor,” and then immediately prescribe a fixed BMI for everyone without qualification.

Jtsummers 4y ago
Indeed, especially the 22 BMI target. For me (5'10") that would mean 155lbs, I'd have to shed (going by my scale which estimates body fat percentage) around 28 lbs of fat (I'm at 15% fat right now, so 28 lbs would get me to 0% which is unhealthy) and 7lbs of other weight to hit that target. Could I lose some weight? Sure. But I won't. Back on the exercise habit after a few months off and I'm getting slimmer but my weight is staying the same, as I would expect it to based on my previous experience (I pack on muscle easily). BMI is a useful heuristic (BMI over 30 and not a powerlifter? Probably unhealthy, let's look at other characteristics and see how unhealthy and how to address it) but a terrible target until you know your own body.
- 11235813213455 4y ago
  > until you know your own body that part is tricky, takes a lot of time, experiments But also I think the body shape makes a big diff, I have very thin limbs, long legs, my best BMI is between 17 and 18, without limiting myself in food quantity (I alwways eat as much as I can, tho I naturally like to eat 1 or 2 meals a day max)
- otherme123 4y ago
  I'm 185 cm (6'1") and 73 kg (161 lbs), for a BMI of 21.3. I still have more than 0% fat, but I'm certainly slim. I don't have to fight at all to keep my weight as it is, and I'm healthy. You say 30 BMI, but in my experience unless you are lifting a lot of weights 25 is the upper limit. Ten years ago I hit 25 BMI, and despite feeling "normal" there were already the first signs of being fat: thights always red, sweaty all day and way less resistance than today. I lost 15 kg (33 lbs) not by doing crazy exercise, but by cutting 100% of shitty food and eating beyond necesity.
  - Jtsummers 4y ago
    I think you're agreeing with me but I'm not sure. I said you have to know your body, which you seem to. For your body 25 BMI is an upper limit, for my body 25 BMI is a lower limit unless I'm losing muscle mass or going to unhealthy body fat percentage levels. Which is why I also said BMI is a poor target. 22 BMI, for me, would be an awful target. I'd be gaunt and have to lose a lot of muscle mass, not just fat (which I don't have a lot of to lose). Even bringing body fat percentage from 15% to 10%, which is still healthy, would only get me down to about 180lbs. That would leave me 25lbs over the target for a 22 BMI. That's my body, not yours, not anyone else's. I've learned what is healthy for me and have set goals and expectations around that. I wouldn't expect yours, or anyone else's, to be the same. You've realized that 25 BMI is too high for you, great. Now you know, but that doesn't apply to everyone. And the original poster in this thread claiming everyone should be at 22 BMI is clearly also speaking about a particular experience which is not applicable to everyone, but writing as if it is.
  - gadders 4y ago
    My BMI is 31 but my body fat % is 18%. I've been lifting weights seriously for 12 years, since I turned 40, but I would never be mistaken for a bodybuilder.
  - peapicker 4y ago
    "...in my experience unless you are lifting a lot of weights 25 is the upper limit.." I get you... I'm 6'0" (183cm) and 212 lbs (96kg) (BMI=29). I'm at 17% body fat and am working toward 10%, but also have been lifting weights heavily. I just got down to size 32 jeans (82cm waist) but have a 48.5" chest (123cm) and 15.5" (40cm) biceps. I still wish to lose 15-20lb more, but then I'd be at 195lb and about 8% body fat -- with a BMI of ~27. (Assuming I don't add more muscle at the same time.) It is a lot better than a 15 months ago when I made my life change - I was 240lb (109kg) and 38% body fat, and pushing a 38" (96cm) waist, truly obese. And I felt like shite. I am surprised how much I have come to love weightlifting, rowing, and eating a diet better balanced towards low-caloric density foods (lots of veggies) and lean protein. And I am more surprised at how quickly my body changed, considering I'm now just over 50.
checker659 4y ago
> would read an article Or, did they?
Symmetry 4y ago
Yes. BMI is your weight divided by height squared. Which is really weird when you consider that humans are 3D objects! So you should naturally expect that a taller person will have a higher BMI than a shorter person even with the exact same proportions. In practice humans who are taller tend to be skinnier so we'd ideally use something close to the 2.5th power but that math would have been impractical for the 19th century clerks who were the first consumers of BMI information.
- meew0 4y ago
  Humans are 3D objects, but fat is not distributed equally throughout the body. Most fat is subcutaneous fat, i.e. located right below the skin. Its abundance can therefore be approximated by body surface area, which is proportional to height squared.
  - naniwaduni 4y ago
    This might be a nice explanation of it didn't fail to agree empirically with reality, where in fact there is a significant cubic component which gives rise to the "something close to the 2.5th power" that GP suggests.
- sorenjan 4y ago
  A few years ago I read a paper where they checked the correlation between CT measured body fat percentage and a lot of easily measured and calculated figures, in the same style of BMI (w/h²). I haven't been able to find it again, but if I remember correctly BMI was actually pretty good, although worse for women than for men, and the best measurement included waist circumference.
  - edflsafoiewq 4y ago
    Waist-to-height ratio is surprisingly good: your waist should not be more than half your height. Simple to measure too, since you only need a piece of string.
  - Buttons840 4y ago
123pie123 4y ago
BMI really wasn't thought of for individuals >The interest in an index that measures body fat came with observed increasing obesity in prosperous Western societies. Keys explicitly judged BMI as appropriate for population studies and inappropriate for individual evaluation. https://en.wikipedia.org/wiki/Body_mass_index https://en.wikipedia.org/wiki/Body_mass_index
Levitz 4y ago
The article does also say: >When a team of researchers adjusted BMI to take muscle mass into account back in 2018, then associated this corrected measure with mortality risk, they found that the “U” mostly transformed into a straight line.

Jtsummers 4y ago

Indeed, especially the 22 BMI target. For me (5'10") that would mean 155lbs, I'd have to shed (going by my scale which estimates body fat percentage) around 28 lbs of fat (I'm at 15% fat right now, so 28 lbs would get me to 0% which is unhealthy) and 7lbs of other weight to hit that target. Could I lose some weight? Sure. But I won't. Back on the exercise habit after a few months off and I'm getting slimmer but my weight is staying the same, as I would expect it to based on my previous experience (I pack on muscle easily). BMI is a useful heuristic (BMI over 30 and not a powerlifter? Probably unhealthy, let's look at other characteristics and see how unhealthy and how to address it) but a terrible target until you know your own body.

11235813213455 4y ago
> until you know your own body that part is tricky, takes a lot of time, experiments But also I think the body shape makes a big diff, I have very thin limbs, long legs, my best BMI is between 17 and 18, without limiting myself in food quantity (I alwways eat as much as I can, tho I naturally like to eat 1 or 2 meals a day max)
otherme123 4y ago
I'm 185 cm (6'1") and 73 kg (161 lbs), for a BMI of 21.3. I still have more than 0% fat, but I'm certainly slim. I don't have to fight at all to keep my weight as it is, and I'm healthy. You say 30 BMI, but in my experience unless you are lifting a lot of weights 25 is the upper limit. Ten years ago I hit 25 BMI, and despite feeling "normal" there were already the first signs of being fat: thights always red, sweaty all day and way less resistance than today. I lost 15 kg (33 lbs) not by doing crazy exercise, but by cutting 100% of shitty food and eating beyond necesity.
- Jtsummers 4y ago
  I think you're agreeing with me but I'm not sure. I said you have to know your body, which you seem to. For your body 25 BMI is an upper limit, for my body 25 BMI is a lower limit unless I'm losing muscle mass or going to unhealthy body fat percentage levels. Which is why I also said BMI is a poor target. 22 BMI, for me, would be an awful target. I'd be gaunt and have to lose a lot of muscle mass, not just fat (which I don't have a lot of to lose). Even bringing body fat percentage from 15% to 10%, which is still healthy, would only get me down to about 180lbs. That would leave me 25lbs over the target for a 22 BMI. That's my body, not yours, not anyone else's. I've learned what is healthy for me and have set goals and expectations around that. I wouldn't expect yours, or anyone else's, to be the same. You've realized that 25 BMI is too high for you, great. Now you know, but that doesn't apply to everyone. And the original poster in this thread claiming everyone should be at 22 BMI is clearly also speaking about a particular experience which is not applicable to everyone, but writing as if it is.
- gadders 4y ago
  My BMI is 31 but my body fat % is 18%. I've been lifting weights seriously for 12 years, since I turned 40, but I would never be mistaken for a bodybuilder.
- peapicker 4y ago
  "...in my experience unless you are lifting a lot of weights 25 is the upper limit.." I get you... I'm 6'0" (183cm) and 212 lbs (96kg) (BMI=29). I'm at 17% body fat and am working toward 10%, but also have been lifting weights heavily. I just got down to size 32 jeans (82cm waist) but have a 48.5" chest (123cm) and 15.5" (40cm) biceps. I still wish to lose 15-20lb more, but then I'd be at 195lb and about 8% body fat -- with a BMI of ~27. (Assuming I don't add more muscle at the same time.) It is a lot better than a 15 months ago when I made my life change - I was 240lb (109kg) and 38% body fat, and pushing a 38" (96cm) waist, truly obese. And I felt like shite. I am surprised how much I have come to love weightlifting, rowing, and eating a diet better balanced towards low-caloric density foods (lots of veggies) and lean protein. And I am more surprised at how quickly my body changed, considering I'm now just over 50.

checker659 4y ago

> would read an article Or, did they?

Symmetry 4y ago

Yes. BMI is your weight divided by height squared. Which is really weird when you consider that humans are 3D objects! So you should naturally expect that a taller person will have a higher BMI than a shorter person even with the exact same proportions. In practice humans who are taller tend to be skinnier so we'd ideally use something close to the 2.5th power but that math would have been impractical for the 19th century clerks who were the first consumers of BMI information.

meew0 4y ago
Humans are 3D objects, but fat is not distributed equally throughout the body. Most fat is subcutaneous fat, i.e. located right below the skin. Its abundance can therefore be approximated by body surface area, which is proportional to height squared.
- naniwaduni 4y ago
  This might be a nice explanation of it didn't fail to agree empirically with reality, where in fact there is a significant cubic component which gives rise to the "something close to the 2.5th power" that GP suggests.
sorenjan 4y ago
A few years ago I read a paper where they checked the correlation between CT measured body fat percentage and a lot of easily measured and calculated figures, in the same style of BMI (w/h²). I haven't been able to find it again, but if I remember correctly BMI was actually pretty good, although worse for women than for men, and the best measurement included waist circumference.
- edflsafoiewq 4y ago
  Waist-to-height ratio is surprisingly good: your waist should not be more than half your height. Simple to measure too, since you only need a piece of string.
- Buttons840 4y ago

123pie123 4y ago

BMI really wasn't thought of for individuals >The interest in an index that measures body fat came with observed increasing obesity in prosperous Western societies. Keys explicitly judged BMI as appropriate for population studies and inappropriate for individual evaluation. https://en.wikipedia.org/wiki/Body_mass_index https://en.wikipedia.org/wiki/Body_mass_index

Levitz 4y ago

The article does also say: >When a team of researchers adjusted BMI to take muscle mass into account back in 2018, then associated this corrected measure with mortality risk, they found that the “U” mostly transformed into a straight line.