Why BMI is flawed -- and how to redefine obesity

[sl8]

https://www.nature.com/articles/d41586-023-03143-x

NEWS FEATURE
11 October 2023

Why BMI is flawed — and how to redefine obesity

The main diagnostic test for obesity — the body mass index — accounts for only height and weight, leaving out a slew of factors that influence body fat and health.

McKenzie Prillaman

[...]

BMI, which is calculated by dividing weight by height squared, has been used for several decades as an international standard to determine healthy weights. It serves as a proxy for body fat, and higher numbers can indicate increased risk for metabolic disease and death.

But BMI does not measure body fat, and it also ignores factors that affect how healthy someone is at a given weight, including age, sex and race. Not everyone with a high BMI has poor health or a raised risk of death1–3.

That’s why there is a small but growing movement to go beyond BMI when diagnosing and treating obesity, which the World Health Organization (WHO) recognizes as a chronic disease. In June, the American Medical Association (AMA) called for more weight-related metrics to be used in conjunction with BMI owing to its imperfections and questionable history.

But, with global rates of obesity having tripled over the past 50 years, and a wave of cutting-edge weight-loss drugs now hitting the market, a high BMI still reigns as the main criterion for obesity treatment. Specialists worry that the surging demand for the drugs will exacerbate reliance on BMI as a solo diagnostic tool.

[...]

[Doodley]

1. Why complicate something that is uncomplicated and an accurate measure in most cases?

[Alpeduez21]

4. Your waist circumference should not exceed your height

Last edited Wed Oct 11, 2023, 08:39 AM - Edit history (1)

simple and more accurate.

Correction ‘1/2’ your height

[mitch96]

13. +1 agree. All the bmi tells me is I'm too short :)..nt

[hlthe2b]

2. There was a slide show created for a national conference I attended a few years back showing

the countless numbers of the most elite (and muscular) athletes, which BMI as a measure incorrectly records as obese or even "morbidly obese" given the failure to account for lean muscle mass. While the point could have been made in a few slides, it went on for some time in a ludicrous bit of mockery. A change in metric is long overdue.

[Doodley]

3. They know they don't need to lose weight, so it really doesn't matter. For the people in which

it does matter, can you think of a more effective measure?

[Alpeduez21]

5. But the medical staff and insurance companies will look at the

and act in accordance with the number listed regardless of other mitigating factors.

[hlthe2b]

11. Yes, they DO

[Doodley]

15. I think medical professionals are smarter than that.

[NickB79]

21. Not in my case

I'm a BMI of 27-28, technically overweight, but it's because I have muscle.

So when I failed my BMI for my work's annual health screening assessment, it then asked for waist circumference. That passed, so no insurance issues.

If you're failing both BMI and waist circumference, that's a bad situation.

[hlthe2b]

8. Read the article. Similar problems are developing for monitoring those on Ozempic/Wygovy

Not to mention the fact that the overly simplistic measure doesn't work for a significant percentage of the population renders it sufficiently unreliable to require us to look at alternatives or at least additional measurements. Even simple waist circumference (v hip measurement) affords more consistent and useful data.

[Doodley]

16. BMI basically tells you if somebody is overweight or underweight, taking into account height.

Yes, it won't be accurate in all cases, and doctors are smart enough to know if their patient is an athlete and has more muscle weight than most people.

[hlthe2b]

18. Read the science on it.

It is the weakest measure that has ever been used to address obesity in the individual. As was explained on this thread previously, it was created as a population-based (cohort) assessment where it has some utility.

Even waist to hip measurements are more valid.

[Doodley]

19. So weighing somebody (and obviously taking height into account) isn't a good way of seeing if

somebody is a healthy weight?

[mitch96]

14. Yup, if you go by BMI Brady and Gronk are over weight...HA!! nt

[NickB79]

20. And people in that elite group are a fraction of a percent of the population

We will likely never have an easy to use system that accurately assesses every person in a population. There will always be outliers.

The BMI scale has some discrepancies in the overweight category, where muscular individuals can hit as overweight. I know; I'm in that group. So, waist circumference can be used instead, and is in fact already a better method overall.

But once you pass a BMI of 30, into obese range, no amount of adjustments to the measurement methods change that. If there are people hoping a new method of measurement will suddenly tell them their weight isn't actually a problem after all, they'll be sadly disappointed with this new system.

[Alpeduez21]

6. I call it the Bullshit Medical Indicator.

My doctor has stopped using it in discussions with me. The problem with it is it was created as a means of statistical analysis of populations. It was never intended to be a medical diagnosis. A mathematician came up with it and, well, here we are.

[hlthe2b]

9. Yes. It was created for population assessment and has some utility there.

[Doodley]

17. But I assume your doctor wants to know the weight of his patients. That is a basic when

delivering healthcare. Now, knowing the weight of patients only becomes useful when factoring in height. I don't see anything wrong in that.

[njhoneybadger]

7. This has been a right wing talking point for years.

[hlthe2b]

10. I beg to differ. It is position of the medical community at large to replace or at least supplement

with additional measures including waist:hip circumference where lean body mass % is not practical/measurable.

I am not a RW meme, but I am a medical professional, so STOP IT!

[Joinfortmill]

12. Makes a lot of sense to me.