The last time the Standard BMI was officially updated through proper, official channels was in 1998 (1, 2, 3). At that time, the NIH changed the threshold for “overweight”, officially lowering it to a BMI of 25 and aligning it with World Health Organization guidelines. The only thing the Standard BMI does, via height and weight, is estimate body fat to assess health risks.
That is literally the only thing the BMI does, estimate body fat to assess health risks (4, 5, 1, 3). It does nothing else (no, it does not estimate health, only healthy weight). Yes, the accuracy of the BMI is debatable, for sure. However, the simple definition of the Standard BMI is not debatable — it is set in stone until changed via official protocol.
This is the current official Standard BMI scale:
18.49 or less – underweight, not a healthy weight due to too little regular white/yellow body fat (common adipose tissue)
18.5 to 24.99 – normal weight, healthy weight due to no excess regular white/yellow body fat (common adipose tissue)
25 to 29.99 – overweight, not a healthy weight due to too much/excess regular white/yellow body fat (common adipose tissue)
30+ – obese, not a healthy weight due to way too much/excess regular white/yellow body fat (common adipose tissue)
In 2016, the NIH released its first-ever (initial) definition for normal-weight obesity (skinny fat)(6):
“Normal-weight obesity syndrome is characterized by excess body fat in individuals with adequate body mass index (18.5-24.9 kg/m(2))”
Which directly contradicts the Standard BMI definition (1, 2, 3, 4, 5). No official change to the BMI happened – the BMI definition/scale did not change.
No, it does not. Waist-to-height ratio does not measure muscle in any capacity. You have no idea how much muscle you were born with or without (skinny fat). You have no idea how your muscle compares to the average, because there is no baseline average to compare it to. You have no idea if your body falls within "normal" phenotype range, because there is no standardized baseline phenotype to compare it to. The next time you see your doctor, ask them how much muscle you were born with, how it compares to the average, and how it compares to the average phenotype...let us all know what they say...
Yes, BMI is a limited, inaccurate proxy measure. But it is the only currently NIH-accepted method, and has not been officially changed by the NIH since 1998.
Lean body mass (LBM) – DEXA, InBody, etc. – is a composite of all non-fat body tissue. it is also not a direct measure of muscle tissue. Like BMI and waist-to-height ratio, LBM is an inaccurate proxy estimate at best.
As of September 13, 2026 –
I wish more people would realize that waist to height only really works for people with a tendency towards BMI-style obesity.
I have virtually no white/yellow fat. My scale says my body is 4.5% fat. I have lean muscle and do endurance training. But I can tell when my muscle is deteriorating because my joints become too loose, and when I get too much interior fat because it presses on my intestines and kidneys. Scale and waist to height both say I’m an Olympic level athlete level of fit… but I’m just slightly above average fit with unusual genetics. I still have to watch my cholesterol, still have to watch my heart, and I know that if I stop exercising for a few weeks, it will severely impact my health without being outwardly very visible.
Hopefully we can find some diagnostics for useful health baselines and tracking for all this. Right now, listening to my body is the most quantitative solution I’ve found.