Health
BMI for Indians: What the Number Means and Misses
Meera and Arjun both come out at a BMI of 25.9. Same number, same category on every chart. And yet if you put them side by side, you'd probably worry about one of them and not the other.
Both are made up, but the arithmetic is real, and it shows the whole problem with BMI in one go. Here's the working.
Two people, one number
Meera is 162 cm and weighs 68 kg. Her waist measures 88 cm. Arjun is 178 cm, weighs 82 kg, has an 84 cm waist and lifts weights four days a week.
BMI is weight in kilograms divided by height in metres, squared.
- Meera: 1.62 × 1.62 = 2.6244. Then 68 ÷ 2.6244 = 25.9.
- Arjun: 1.78 × 1.78 = 3.1684. Then 82 ÷ 3.1684 = 25.9.
Now a second calculation: waist divided by height, both in centimetres.
- Meera: 88 ÷ 162 = 0.54.
- Arjun: 84 ÷ 178 = 0.47.
A commonly used rule of thumb is to keep your waist under half your height, a ratio below 0.5. Arjun is under it. Meera is over it, by about 7 cm (half her height is 81 cm). BMI said they were identical. The tape measure says they aren't.
That's not a reason to throw BMI away. It's a reason to treat it as a first question, not an answer.
What BMI actually is
It's a screening ratio. It was built for studying populations, where a crude measure that costs nothing is useful. Everyone has a scale and a height. Nobody needs a scanner.
It cannot see what your weight is made of. Muscle, fat, bone, water: all of it is just kilograms. It cannot see where fat sits. It doesn't know your age or sex. So it works like a smoke alarm. It's useful when it goes off, and it can go off for toast.
The other thing it can't do is predict you. Plenty of people with a high BMI have normal blood sugar and cholesterol, and some people with a normal BMI don't. Across a large group the average risk climbs with BMI. For one person, it's a nudge to check, not a forecast.
Why India uses 23 and 25, not 25 and 30
The WHO adult categories most charts print are:
| Category | WHO cutoff | 2009 Indian consensus |
|---|---|---|
| Underweight | below 18.5 | below 18.5 |
| Normal | 18.5 to 24.9 | 18.5 to 22.9 |
| Overweight | 25 to 29.9 | 23 to 24.9 |
| Obese | 30 and above | 25 and above |
The Indian column comes from a 2009 consensus statement for Asian Indians. The reasoning is that, at the same BMI, South Asian adults tend to carry more body fat, and more of it around the abdomen, than the populations the WHO cutoffs were mostly built on. So risk for type 2 diabetes and heart disease starts showing up at a lower BMI. The consensus moved the lines down to reflect that.
Look at what this does to Meera. At 162 cm, the WHO "normal" band tops out at 65.3 kg (24.9 × 2.6244). The Indian band tops out at 60.1 kg (22.9 × 2.6244). She weighs 68. Under WHO she's overweight. Under the Indian cutoffs she's in the obese range, and her waist-to-height ratio doesn't argue.
The two tables disagree by design. Neither is "the truth". Pick the one that fits who you are, and don't be alarmed that a calculator using the Indian cutoffs gives a worse-sounding label than the WHO chart on a gym wall. The BMI calculator on this site lets you see both.
Three kinds of people BMI gets wrong
Muscular people
This is Arjun. Muscle is denser than fat, so a trained person can land in "overweight" or even "obese" with a healthy waist. If you train seriously and your waist is well under half your height, a high BMI is probably noise.
Older adults
Two things happen with age. People get slightly shorter, and that pushes BMI up even if weight is unchanged. And muscle tends to shrink while fat holds steady or rises. So an older person can have a perfectly "normal" BMI and still be low on muscle, which BMI can't see. Doctors often read BMI differently after 60 or so, and a very low BMI in an older relative deserves attention too, not applause.
People with central obesity at a normal BMI
This is the one that worries me most, because the reassuring number hides it. Take a hypothetical man, 170 cm, 72 kg. His BMI is 72 ÷ 2.89 = 24.9. Normal by WHO, and only just overweight by the Indian cutoffs. But if his waist is 92 cm, his ratio is 92 ÷ 170 = 0.54, the same as Meera's. Fat stored around the middle is the kind most linked with metabolic problems, and a slim-looking arm and leg can sit alongside it.
How to take the waist measurement properly
Most people do this wrong, and measure where the trousers sit. That's usually below the real waist.
- Stand up straight, relaxed, and breathe out normally. Don't suck in.
- Find the point halfway between the lowest rib and the top of the hip bone.
- Wrap a soft tape level with the floor, snug but not squeezing the skin.
- Measure twice. If the two readings differ by more than a centimetre, do it a third time.
Then divide by your height in cm. Use the same units top and bottom, so don't mix inches with centimetres. If you only have inches, 1 inch is 2.54 cm.
Reading the two numbers together
I'd use a simple grid.
- BMI in the normal range, waist ratio under 0.5. Nothing here to chase.
- BMI high, waist ratio under 0.5, and you have a lot of muscle. Probably the BMI is misleading you. Mention it to a doctor at your next routine visit, that's all.
- BMI high, waist ratio above 0.5. Both numbers agree. This is worth a conversation with a doctor, along with a blood sugar and cholesterol check, which tell you far more than either ratio.
- BMI normal, waist ratio above 0.5. The case people skip. Same advice: talk to a doctor, and don't let the normal BMI close the topic.
Notice what's missing from that list. There's no diet, no target weight, no exercise plan. That's deliberate. What's right for a 24-year-old, a person with thyroid trouble and a woman after pregnancy are three different answers, and a website can't give them. A doctor who has your blood reports and history can.
What a calculator can't tell you
None of this diagnoses anything. A ratio of 25.9 is not a disease and 24.9 is not a clean bill of health. BMI is also less meaningful for children and teenagers, who are judged against age and sex growth charts instead, and during pregnancy.
If you want one useful thing to do today, find a tape measure and write down your waist and height. Check it again in six months. A trend in your own numbers, measured the same way, tells you more than any chart you compare yourself to.
This article is general information, not financial, medical or legal advice. See the disclaimer. Spotted a mistake? Email hello@hukhlatri.in and we will check and correct it.