What BMI Actually Tells You — and What It Does Not
BMI is a simple ratio of height to weight. It does not measure fat, and the range used for South Asians is lower than the international one — the least-mentioned fact about it.
BMI is probably the most used and most misunderstood number in health. It is a ratio — a starting signal, not a verdict.
How it is calculated
BMI = weight in kilograms ÷ height in metres squared. Someone weighing 70 kg at 1.70 m has a BMI of 70 ÷ (1.70 × 1.70) = 24.2.
Calculate your BMI→Why the range differs for Indians
This is the part that rarely gets said. The international range treats up to 25 as normal, but in South Asians the risk of diabetes and heart disease starts rising at a lower BMI. Separate, lower cut-offs are therefore used for Asian populations.
| Category | Asian range | International range |
|---|---|---|
| Underweight | Below 18.5 | Below 18.5 |
| Normal | 18.5 – 22.9 | 18.5 – 24.9 |
| Increased risk | 23 – 27.4 | 25 – 29.9 |
| High risk | 27.5 and above | 30 and above |
So a BMI of 24 reads as "normal" internationally but as worth attention in an Indian context.
Where BMI misleads
- Muscular people — athletes read high while carrying little fat
- Older adults — muscle declines with age, so BMI can look normal with more fat
- It says nothing about where fat sits — and fat around the middle matters more
- It does not apply in the same way to pregnancy or growing children
Read it with your waist
Which is why BMI alone is not enough. Waist measurement and waist-hip ratio show where the fat is — often more useful information in an Indian context than BMI itself.
Check your waist-hip ratio→Frequently asked questions
Does BMI measure body fat?+
No. It is only a height-to-weight ratio. Waist measurement and other methods estimate fat better.
What is a normal BMI for Indians?+
On the Asian cut-offs, 18.5 to 22.9 is treated as normal.
Do the same ranges apply to children?+
No. Children are assessed against growth charts for their age and sex.
My BMI is 23 — should I worry?+
In an Indian context that is the start of the increased-risk band. Not alarming, but worth checking your waist and habits.