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.
Yes, BMI is a limited, inaccurate proxy measure.
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, LBM is an inaccurate proxy estimate at best.
As of September 13, 2026 –