That being said, as an American, it really did shock me how fit the majority of people were in Italy when I visited there for the first time last year.
This New England Journal of Medicine chart really does a good job of showing that America has gotten heavier over the years: https://www.nejm.org/na101/home/literatum/publisher/mms/jour...
Because being overweight/obese is normalized because it is seen everywhere, there are tens of millions of people who have no idea they are at an unhealthy weight ... they rightly think they look like everyone else. The BMI is a an easy metric to get people to evaluate if they need to do something about it.
The problem with it is that it’s so commonly responded to with ‘muscle means it isn’t right’.
I used to be fairly fit and fairly strong and a bit too much towards the ‘obese’ category. I remember semi-believing it was muscle pushing me up the scale that far.
I’m now right in the middle of the ‘healthy weight’ category and I’d like to go back and convince my younger self that it’s time to fix the food intake and that muscle isn’t what’s pushing the weight up.
No, but someone who works out the numbers and realizes that the BMI doesn't match them well, or their circumstances well, realizes it calls the study and what it represents into question. Using controversial metrics because they are easily available is counter-productive in the long run, because once people realize you were misrepresenting your credibility is lost. At best it's lazy.
Right now I'm obese. In high school according to the BMI I was almost half-way through overweight edging towards obese, and that was with very little fat, a very active lifestyle, and a visible six-pack. How do I consider studies that make claims about percentages of people that fit into those categories? As extremely ambiguous in what they are actually indicating.
Do Americans have a problem with weight? I think so. Does using false numbers to overestimate the problem help? I don't think so, especially when people realize the metrics leave a lot to be desired.
Think "Reefer madness" and all the bunk science out about Marijuana in the 80's and 90's. Did anyone trust the information coming out at that time? I would hazard most in their teens and twenties didn't, which is exactly who that information was intended to sway.
Trust is important. If people don't trust that what you're saying is accurate because it's easy to point out the shortcuts taken that muddy the results, I think eventually they are going to look at most results about that subject with a grain of salt. At that point they've been trained to do so.
The best ammo against a problem is clear and accurate information. Not fear-mongering and FUD, or even something adjacent that's just imprecise enough to be easily called into question. All that does is cause confusion and arguments over veracity.
How does BMI accuracy scale with age? How does it scale with different ethnic groups? How do these interact? How do you infer an accurate number without knowing these variables and accounting for them and the relative sized of those cohorts?
If the measurements to create the BMI were taken from a statistically valid cross section of the current makeup of Americans, then I would have no problem. But how was the BMI generated? When? With what type of participants?
This article itself notes that Asians experience relatively more problems at a lower BMI. Without knowing what the BMI is tuned to, how an we interpret how it applies to a cross section of Americans for a singular study?
As a measurement of similar studies seeing a change over time, I agree it's less problematic (but could still be affected by trends in physiology over time, possibly from immigration).
I don’t understand why everyone is so quite to dismiss BMI based on edge cases, especially when the finding is backed up by your other evidence.
I've found Body fat % to be a more useful number, it's easy to understand what you'd look like with 10% less body fat - and you won't see many/any athletes with 30%+ body fat. When I first started tracking this I was shocked by the initial number (35%) and managed to work it down to 17% over time, my total weight didn't change by more than 5%.
https://www.businessinsider.com/sumo-wrestlers-obesity-diet-....
For average people BMI is a reliable indicator.
[0]: https://en.wikipedia.org/wiki/Body_mass_index#/media/File:Co...
A lot of non-cardio gym time and protein eating.
As anecdata - I'm on the opposite end of the physical activity spectrum to Tom Brady, I'm also 6'4" and the heaviest I've been is about ~210 lbs. I was definitely starting to feel "a bit too big" at that, and would confidently say I'd feel overweight at 225 lbs, so the scale doesn't feel massively miscalibrated to me.
If a metric had 95% accuracy would that qualify as reliable? I would certainly say so. Especially if the 5% outliers are not random but in fact an extremely obvious edge case?
I do not know how “reliable” BMI is. But elite athletes represent an exceedingly small percent of the population.
My intuition is that BMI is a pretty darn good first approximation. And instances where it’s not good there is supporting evidence.
BMI is a good metric for POPULATION level studies, infact it was designed explicit for that purpose
So me calculating my individual BMI then making health judgments solely on that number is stupid.
However A person calculating the BMI of all persons in a Population then using those numbers to judge to overall condition of the population is valid