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.
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.
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.
Why do we assume that fat is bad for you, but muscle is always good for you. The blood necessary to maintain excessive muscle is still excessive to normal humans, and may put strain on the heart. Only our skin grows with our muscles, other organs do not grow in tandem.
I've always thought that while BMI is crude, it still is reasonable for measuring metabolic syndrome, considering that many of the things associated with heart problems involve the needing a powerful heart, when adding any mass whatsoever will necessarily increase the work the heart must do.
Do you have anecdotes or other evidence of someone experiencing heart issues because they were too muscular?
It seems to me that in the usual case where a person develops muscle mass by working out, this isn't a problem because whatever "blood necessary to maintain excessive muscle" is negligible in the face of the body adapting to improve the cardiovascular system in order to serve muscular oxygen needs during workout. Of course, heart problems due to an unhealthy person ramping up exercise too quickly is a concern, but this is separate from your concern.
One also observes that athletes in general have lower heart rates than the average person; whatever additional burden their muscles impose, their cardiovascular system is way more adapted to handle that due to exercise.
My argument is that we should not assume that extra mass from muscle does not impose similar health problems from fat. If we are going to say that, it should be demonstrated. A fit person doesn't need to weight 30+lbs more than standard overweight section of the BMI. If they do, they will be a very non-standard human.
Here are some things I found in a brief glance at google scholar. There appears to be a condition called Athlete's heart, but I dunno:
The first link describes heart problems perhaps arising from intense exercise, which is a different thing that heart problems arising from muscle mass.
The second describes the same thing:
> Several middle-aged and older men trying to improve their physical fitness by weightlifting have presented for repair of severe mitral regurgitation, some of whom stated that they remembered feeling a pop in the chest while weightlifting, which was the start of their dyspnea.
> Arterial BP increases most during weightlifting that is accompanied by mechanical compression of blood vessels (such as when bent forward at the waist or squatting) and when accompanied by a Valsalva maneuver.
Neither of these papers link them to muscle mass but to the stress of high-intensity exercise itself, which I have already addressed.
I agree that we should not assume things, but in the lack of cursory evidence, I would still stand by my argument that in the normal case where muscle mass is formed from working out, such workout stresses and modifies the cardiovascular system to such an extent the result is a body that is more than capable of handling whatever stress that muscle at rest imposes on the heart.
Once again I reiterate my cursory evidence to my argument, that athletes' cardiovascular system are generally so much more efficient and less taxed than the general population that their hearts beat at 3/4 the average heart rate.
It seems like athlete's heart syndrome is a benign condition.
Actually, it appears BMI is more accurate for women than for men. I'm guessing because men have more variability in their muscle mass.
Overall, I think BMI looks like a pretty useful metric considering how easy it is to measure. That would explain why it sticks around despite being frequently criticized.
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.
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.
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.
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.
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.
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.
"...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.
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.
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)
>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.
>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.