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.
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.