Why a 'normal' BMI can still hide diabetes risk in Indians

A South Asian adult with a BMI of about 24 carries roughly the same type 2 diabetes risk as a white European with a BMI of 30. Here is why, and the two numbers worth checking instead.

Most of us learnt one number for a healthy weight: keep your BMI under 25. For Indians, that line is drawn in the wrong place.

A study of nearly 1.5 million adults in England found that a South Asian person with a BMI of 23.9 had the same risk of developing type 2 diabetes as a white person with a BMI of 30 ¹. Put simply, someone who looks "a little soft around the middle" by Indian standards can carry the diabetes risk that doctors in Europe would only flag in clear obesity.

The size of the problem at home

India's national metabolic health survey, the ICMR-INDIAB study, tested 113,043 adults between 2008 and 2020. It found diabetes in 11.4% of adults and prediabetes in another 15.3% ². In absolute numbers that is about 101 million people with diabetes and 136 million on the way ³.

The same survey found abdominal obesity in 39.5% of adults, well above the 28.6% with generalised obesity by BMI ². That gap is the clue. Many Indians store fat around the organs while their overall weight stays unremarkable.

Two doctors, same BMI, very different bodies

In 2004 the diabetes researchers Chittaranjan Yajnik and John Yudkin published a short piece in The Lancet with a striking picture: two physicians, one Indian and one British, both with a BMI of 22.3. The British doctor had 9.1% body fat. The Indian doctor had 21.2% ⁴⁵.

They called it the Y-Y paradox, after their initials. Same height-to-weight ratio, more than double the fat.

The pattern shows up remarkably early. The Pune Maternal Nutrition Study compared newborns in India with babies born in the UK and found that Indian babies were smaller and lighter, yet held on to their fat. They were "thin-fat" from birth ⁶.

The scale tells you how heavy you are. It does not tell you what you are made of.

Why fat location matters more than weight

Fat stored deep in the belly and in the liver behaves differently from fat under the skin of the hips and thighs. It is more closely tied to insulin resistance, which is the first step towards type 2 diabetes. With less muscle to soak up blood sugar and more fat in the wrong places, the body struggles with glucose at a lower weight.

This is why health bodies have redrawn the lines for Asian populations:

• In 2004 a World Health Organization expert group found that many Asian populations show raised risk from a BMI of 22 to 25, and suggested 23 and 27.5 as extra points for public health action ⁷.
• In 2025 Indian experts went further. Their revised definition treats a BMI above 23 as the starting point of obesity for Asian Indians, and adds waist size and waist-to-height ratio to the assessment ⁸.

The two numbers worth checking

1. Your waist. Measure at the level of your belly button, standing relaxed, after breathing out. The Indian cut-offs for abdominal obesity are 90 cm or more for men and 80 cm or more for women ⁸.

2. Your waist-to-height ratio. Divide your waist by your height, in the same units. Above 0.5 is a warning sign ⁸. An easy way to remember it: keep your waist under half your height.

Neither needs a lab, a scale or an app. A tailor's tape and a calculator are enough.

What actually helps

The good news is that the fat that matters most is also the fat that responds well to training and food changes.

• Build and keep muscle. Muscle is the body's biggest store for blood sugar. Two or three strength sessions a week, done properly, give your glucose somewhere to go.
• Walk after your biggest meal. Even ten minutes after dinner measurably lowers the blood sugar spike. We look at the evidence in this piece on post-meal walks.
• Shift a little of your plate. The national survey also found that Indian diets are very high in carbohydrate and low in protein, and that swapping some carbohydrate for dairy, egg or other protein was linked with lower diabetes risk ⁹.
• Get tested, even if you feel fine. Prediabetes rarely causes symptoms. If your waist is above the cut-off, a fasting glucose or HbA1c test is a simple, inexpensive check.

A BMI of 24 is not a reason to panic. It is a reason to pick up a measuring tape.

General information for healthy adults, not medical advice. Speak to a doctor before changing your training or diet if you have a health condition, are pregnant or take regular medication.