Comment by AStrangeMorrow
1 day ago
Yes, it is a pretty high level metric with good correlation a bunch of diseases, but really many of these is because it is ALSO correlated to percent of fat, which is often the more relevant metric. But as you said BMI is so much simpler to measure.
Many active gym people have pretty high BMIs but fairly low fat (because muscle is dense), and unsurprisingly have better outcomes than the average person (if you ignore the share that uses/overuses anabolic steroids and co)
> Many active gym people have pretty high BMIs but fairly low fat
I think this is greatly exhaggerated.
Yeah you can put on as much muscle as Arnold and have a FFMI of about 27 then maybe have a BMI of 34 if you have 20% body fat.
But a very gifted natty might cap out at maybe 24 with a BMI of 30 at 20% bodyfat. But let's be realistic. This is not "many active gym people". This is the guy winning the local strongman meet.
Yes a couple of years training for most people can add a couple of points to BMI but I think people exaggerate how much this is. Go look at a 20lb brisket at costco - you don't see people with that much extra muscle all that often.
I do agree to some extent, but really the overweight threshold for BMI is 25. And 30 for obese.
At 6 feet / 183 cm that it takes 184 lbs / 83 kg to be overweight. From what I could find, for regular gymgoers the typical weight for people around 6feet is 180-190lbs, which put many people around the overweight threshold. I am myself at 24.9, and while not skinny I am definitely in the skinnier half of the people at my local gym.
Going from your size to 27 means putting on 10kg of muscle. That's a beef brisket. Half the guys in the gym don't have that much more musle than you.
Yeah really well muscled guy being BMI 27 is probably ok but by 30 it's not natural muscles that are making the scales go up.
I very much disagree. Overweight starts at 25 BMI, and obese at 30. Most regular gym goers in my social circles maintain <20% body fat, and are classified as overweight based on BMI. In the US weightlifting is quite popular, and it’s not hard to gain enough muscle mass to classify as overweight. I’ve been “overweight” at 27 BMI going on >10 years now, with actual body fat fluctuating ~12-18%. I’ve had doctors tell me I need to lose weight because my BMI is too high, while I had visible abs. It’s a common theme among other casual weightlifters I know. I don’t think BMI is particularly useful for anyone that has done more than a year of basic barbell strength training cycle.
My completely made up rule is you get an extra point for every plate you bench (or squat etc). Its not a dramatic difference. If you bench 225 you’re not overwreight till 27 BMI, which iirc used to be the actual cutoff until they narrowed it.
Obese is hard. Overweight is easy if you walk, take the stairs, do the occasional pushup, and play something like hockey once week. Source: my entire life.
N=1
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> Many active gym people have pretty high BMIs but fairly low fat (because muscle is dense),
I’ve been in the overweight BMI category with low body fat by being active at the gym and focusing on diet. It takes some work to get there.
If I check the calculators for the obese BMI range, there was no way I could get there without either gaining a lot of fat on top of the muscle. The amount of muscle required to have an obese BMI with healthy amount of fat is absurd.
I believe evidence points towards absolute level of fat being more important than % for overall health.
E.g. 20% bodyfat at 250lbs is still a lot of fat.
Of course it's difficult to ever get very high on absolute fat if at 15% or below.
Not sure I follow the logic here, but happy to be proven wrong if I'm misunderstanding. It's not intuitive to me that a 300 lb. person at 20% body fat is generally at the same risk as a 200 lb. person at 30% body fat.
Fat is inherently unhealthy for you beyond some low baseline level.
Additional muscle is positive for health, but only up to some reasonable threshold. There is no health benefit to having very high levels of muscle, and in fact it may be negative for your health at extreme levels. E.g. many bodybuilders have trouble breathing, sleep apnea etc.
Both people in the example have 60lbs of fat. 1lb of muscle doesn't cancel out the negative health effect of 1lb of fat
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Do you have a citation for that? I've had thoughts in a similar direction (specifically around the upper/lower intervention points) but have had no luck finding data.
Its not just absolute amount of fat though you also have to account for intra abdominal fat being much worse metabolically than subcutaneous fat.
Does that have to do with sizes of the heart and few other organs apparently being largely constant regardless of height?