BMI is a surprisingly relevant metric for many things as it's a comparison between volume (weight) and surface area (height ^2). And yes, short people do have an inherent advantage there which for example possibly relates to how small dogs tend to live longer.
Because muscle and bone are denser than fat, and exist in higher proportion in fitter people, two people could easily have identical BMIs even though one is a powerlifter with 5% body fat and the other is mostly made of Cheetos.
Yes, but powerlifters with 5% body fat are far more rarer than Cheetos-munging fat people.
So the possibility of such false positives is not that high, making still a good heuristic. Not to mention: if one is a thin, mostly-muscle powerlifter type, they already know they are not obese...
BMI is a horrible metric because it doesn't take body composition into account. I can't believe I was once almost considered obese with a body fat of less than 5%. 5'10" at 200-210.
My BMI is 26+ and I run ~8 miles/day. It can be pretty far off for larger built people...
I clearly remember asking my gym teacher in middle school why my BMI suggests I was fat even though I clearly wasn't. He then proceeded to tell the entire class "he's a good example of someone who's labeled as fat, but isn't." Somewhat embarrassing.
My employer had one of those physical checkups for a lowered rate on insurance. I'm 5'10", 215 pounds[1]. The doctor sighed and said that he was required to tell me that according to BMI, I was obese and should consider losing weight. We had a good laugh about it.
My body-fat percentage is definitely not 5%, though. My guess is that it's around 14-15%. Everyone drastically underestimates how low their body-fat percentage is, and I am not a bodybuilder. I lift heavy and like pasta.
Your heart does not care if it's supporting fat or muscle it must pump blood for both. Further skin and colorectal cancer are both surface area and don't care about fat vs. mussel.
Metabolically muscle is worse as it needs more oxygen and fuel. Which is one of the reasons body builders can often die young from a heart attack.
Taller people tend to have larger hearts and wider artery's which makes a difference. It's pressure = flow rate / diameter of pipe ^ 2. So, as you gain weight your arteries can get wider or the pressure can increase.
Gaining weight increases skin, which is why skin reduction surgery happens for people that lose lot's of weight. GIS for skin folds.
Weight / height ^2 is a proxy for both it's far from perfect, but it's also really easy to collect.
