Why obesity starts at a BMI of 25 in India

You went in because something felt wrong. Blood was taken. The result came back, somebody said it was normal, and that was the end of the conversation.

Normal is doing a great deal of work in that sentence, and almost nobody explains what it means.

What a reference range actually is

A reference range is not a statement about your health. It is a description of a group of people.

Somebody measured a few hundred or a few thousand people who were considered healthy, looked at where the middle 95% of them fell, and drew a line at each end. Your result is then compared against that group. Inside the lines, normal. Outside, flagged.

Which raises a question worth asking out loud. Who was in the group?

Where India has already answered that

For body weight, the answer is settled and it is written into Indian clinical practice.

Obesity in India is defined from a BMI of 25, where the WHO threshold is 30. The reason is that metabolic risk arrives at a lower weight in Indian bodies, so a threshold built elsewhere lets too much of it through.

Read that figure carefully, because it is easy to misread. Those are not two different groups of women. It is one group, 3,877 apparently healthy Indian women aged 18 to 40, counted twice (Ganie et al., 2023).

Under one standard, eight women in a hundred are in the obese range. Under the other, four in ten are.

Nothing about the women changed. The line moved.

Where the evidence stops cooperating

Thyroid is where you would expect the same story, and it is where things get more honest and less satisfying.

The Indian figure most often quoted comes from the ICMR PCOS task force, which put the normal TSH range for reproductive-age Indian women at 0.52 to 4.16 mIU/L (Ganie et al., 2023). Common Western ranges run to about 4.5. Set those two numbers beside each other and it looks like the BMI argument all over again.

Two things get in the way.

The sample is smaller than it looks. That study clinically evaluated 3,877 women, but the reference range itself rests on 848 of them, once lab work and exclusions are accounted for.

The paper declines to make the claim. Its own conclusion says the comparison showed "marginal differences in the normative ranges for the hormones analysed among different populations." The authors examined precisely this question and chose not to say the ranges differ meaningfully.

Why that still matters to you

The argument does not collapse there. It moves somewhere more useful.

In pregnancy, where the consequences of getting this wrong are most serious, the major thyroid bodies already accept the principle. The European Thyroid Association recommended in 2014 that reference ranges be defined for each antenatal centre from local population data, and the American Thyroid Association's 2017 guidance takes the same position.

So the idea that a range should fit the population it is applied to is not controversial. What is missing is the practice.

Most labs print one adult range on every report. The same two numbers for a woman of twenty-four and a woman of sixty-four. The report does not tell you who that range was built from, how old they were, or whether any of them were women.

The question to take with you

None of this means your result was wrong. None of it is a reason to argue with your lab, and none of it is a reason to decide you are ill when a doctor has said you are not.

It is a reason to ask one question that almost nobody asks.

What range was this measured against, and where did that range come from?

Most doctors will not mind being asked. Some will not know, which is worth knowing in itself, because it tells you how much weight the word normal was carrying when it was said to you.

If you have been told your results are normal and you still do not feel right, we have a set of questions for exactly that situation. If you are not sure who to take them to, we have written about which doctor handles what.

What these numbers can and cannot tell you

The BMI finding is solid and it is the strongest thing on this page. It comes from a large, recent study of Indian women, and the two thresholds it compares are both in official use.

The thyroid section is deliberately unresolved, because the evidence is. The Indian normative range rests on 848 women, and that study's own authors describe the differences between populations as marginal. Anyone telling you confidently that Indian thyroid ranges are different is going further than the evidence does.

Whether being Indian changes the TSH range is an open question, and it is one the quoted figure does not settle.