Weight Talk: Fitness, Health and Society

It's just fine. BMI is a proxy measure for overall health and risk of future health problems. Like any global proxy it is not a perfect fit for every situation, but it's a reasonably accurate quick'n dirty screen to go looking for other issues. So it's not a diagnosis in and of itself but it's a pointer to other issues. The sit/stand test would another example of this kind of measure. It's not measuring anything specific, but it's highly correlated with health outcomes. BMI has the advantage of being incredibly easy to measure, and it can be done from historical records where height and weight are available.

So there are problems with it, notably that yes muscle weighs more than fat. So yes, many bodybuilders appear as borderline obese. What this means is that there should be followup as it's a screener. A lot of people think this affects them, but if you aren't lifting 2/3/4, it probably doesn't. Those heavily muscled individuals are so far out on the bell curve they don't affect those of us in the middle 99%.

There are other problems with it, including that it doesn't scale well with height, so it gets wonky if you're taller than 6'5" or so.

Alternatives such as waist-to-hip ratio and waist circumference are better measures for individual diagnosis, but tend to not be favored in the research literature because there are not large population databases available, and historical comparisons are generally not possible.

The idea makes sense I'm theory, but doesn't work in reality. I consider it a psuedo science that stuck around because it was just kind of accepted as true. The numbers just don't scale right for height or muscle.

I have an average height friend who had a doctor tell him he was obese. My friend has virtually no fat on him. Although he's muscular, it's not like he's a body builder or someone you'd look twice at for being out of the norm. Muscle is just dense.

I'm tall. When I was very poor and couldn't afford enough food, I weighed right in the middle of the 'healthy' zone. On multiple occasions a romantic interest saw me with a shirt off and tell me I should eat more. I remember the look well. My ribs were very prominent. BMI tells me I could weigh 30 pounds less and still be healthy! People would voice very serious concern if I got anywhere near that.

I do not trust BMI.

The problems with BMI as it exists aren't horrible. There's flaws in how it was originally built, and unusual bodies can make it useless. But as long as the people using it to screen patients are aware of that, it's a usable first step.

The bad problem with it is twofold. First is the practitioners that don't use it properly as a screening tool rather than an indicator of disease/disorder. Second is random assholes out in the world with no training trying to act like they know enough to use it for anything at all.

The second one is whatever, because people gonna people.

The first one though? It's disturbing. When you're sitting there with a high BMI, and you could pick the md/np/pa up one handed, and they start talking about obesity, that's a very, very bad sign for the provider. And it happens. It happens way more than is reasonable because the people that are providing care are either being taught wrong, or aren't paying attention during college.

BMI as a first step screening tool is very valuable. It gives a simple, easy to use metric to assess risks. But it has to be the first step out of many, even for patients that do have a body that's legitimately overweight or obese. When BMI turns into the sole determinant of how a care provider addresses the patient, the whole thing breaks down. When BMI isn't useful for a patient, and the provider still tries to apply care that isn't appropriate because of the BMI, the system itself is flawed more than BMI itself.

Being real, most people aren't going to be so tall or built that BMI is useless. Most aren't even going to hit the sizes where it starts to be less useful. It is a niche issue. And, in all reality, if you're that tall/big and your doctor is ignoring that he or she could stand on your back and you could still crank out pushups like nothing, the BMI isn't the biggest concern. What else are they ignoring that could cause serious issues rather than just pushing harmless but ineffective dietary advice?

Which, you don't even have to be a serious lifter for that kind of issue. There are obese patients that receive bad care because they're obese, and that's where a doctor starts, but refuses to abandon it or otherwise address an issue that's causing a problem. Like, my buddy going in with digestive symptoms, being told to lose weight, and a year later it turns out it was an autoimmune issue.

Yeah, obesity can cause weird stuff with digestion. But having to wait a year for appropriate testing after switching doctors, that's still bullshit. It's a thing, it happens, and it happens a lot more than it should among disabled patients.

Mind you, it isn't only thing doctors get hung up on like that. You come in disabled, and chances are that a provider is going to keep assuming the original disability is the cause of the new symptoms. Which is fine enough until they give up rather than pivoting to alternate possibilities. But that's only relevant in that it illuminates the underlying problem: that not all doctors/nurse practitioners/physician assistants are graduated with the same skill and knowledge. The patient still has to be their own advocate because providers are still human and humans screw up sometimes, even when they're the best in their field

To expand on this, the original statistical basis for "normal" BMI is deeply flawed:

Along with BMI’s fundamental limitation - its inability to accurately measure body fatness - other limitations existed within Keys’ study. The ages of the cohorts of men were not uniform. The “Bantu” cohort consisted of men aged 31-60 years, the “University of Minnesota students” cohort consisted of men aged 18-24 years, the “Minnesota executives” cohort consisted of men aged 49-59 years, and all other cohorts consisted of men aged 40-59 years. No women were included in the studies and these studies were not properly representative of different ethnicities, races, and backgrounds. Of the 7,426 men included, just 1.56% of them were of South African descent, from the “Bantu” cohort; 13.9% were of Asian descent from the “Japanese farmers” and “Japanese fishermen” cohorts; 43.7% of men were of European descent from “East Finland,” “West Finland,” “Crevalcore, Italy,” and “Montegiorgio, Italy”; 40.78% of the participants were men from the United States from the “Rome Railroad,” “University of Minnesota students,” “Minnesota executives,” “U.S. Ry. sedentary,” and “U.S. Ry., switchmen” cohorts [2]. While there was some representation of different ethnic groups in the 1972 Keys' study, this representation was somewhat random and was greatly outweighed by that of Caucasian men of European descent.

The History and Faults of the Body Mass Index and Where to Look Next: A Literature Review

The statistical averages derived from the foundational study of BMI really only have any meaning if you are a male with European ancestry - no other group was properly represented.