What BMI does and does not tell you
BMI was designed for population statistics, not individual diagnosis. It cannot distinguish muscle from fat, does not locate where fat is stored, and shifts in accuracy across ethnicities and ages. It remains useful as a first screen because it is cheap, repeatable, and correlates with risk at the group level.
- • Waist-to-height ratio below 0.5 is a stronger metabolic-risk signal than BMI alone.
- • Muscular athletes commonly measure BMI 26–30 with body fat under 12%.
- • Some health bodies use a lower overweight threshold (23.0) for South Asian populations.
Using BMI as a tracking number
The most valuable use of BMI is trend, not absolute value. A steady half-point drop over months alongside stable strength usually means fat loss; a rapid drop with strength loss often means muscle loss and warrants a conversation with a clinician or dietitian.
Related guides
Long-form playbooks on the same topic, written by the RevenueLab editorial team.
FAQ
What is a healthy BMI?
The WHO healthy band for adults is 18.5 to 24.9. Below 18.5 is classified underweight and 25.0 and above is overweight, with obesity starting at 30.0.
Is BMI accurate for athletes?
No. BMI counts all mass equally, so a lean, muscular athlete often lands in the overweight band. Body fat percentage or waist-to-height ratio gives a far better read.
Does BMI differ for men and women?
The formula and cutoffs are identical, but at the same BMI women typically carry more body fat than men. That is one reason BMI should be paired with a body-composition estimate.
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