A Unique Risk Profile
South Asians — including people of Indian, Pakistani, Bangladeshi, and Sri Lankan origin — have the highest rates of type 2 diabetes and premature coronary artery disease of any major ethnic group, and they develop these conditions at lower BMI thresholds than other populations. A South Asian with a BMI of 23 — considered "normal" by WHO standards — may have the same metabolic risk as a Caucasian with a BMI of 30.
The Thin-Fat Phenotype
The central driver of the paradox is the "thin-fat" phenotype: South Asians tend to have lower lean muscle mass and higher body fat percentage at any given BMI, and that fat is disproportionately visceral — deposited deep in the abdomen and inside organs like the liver. This combination of low muscle mass (the primary glucose sink) and high visceral fat (a metabolically toxic depot) creates a perfect storm for insulin resistance.
A BMI of 23 in a South Asian is metabolically equivalent to a BMI of 30 in a Caucasian. Standard "normal weight" ranges do not apply.
The Biology Behind the Paradox
Genetic predisposition — GWAS studies have identified multiple loci associated with higher diabetes risk in South Asian populations
Lower beta-cell reserve — pancreatic insulin-producing capacity is inherently lower, meaning the pancreas fails earlier under metabolic stress
Higher lipoprotein(a) [Lp(a)] — a genetically determined, highly atherogenic particle that is 2–3x higher in South Asians on average
Lower adiponectin — the "good" adipokine that protects against insulin resistance is naturally lower
Early-life programming — maternal undernutrition during pregnancy epigenetically programmes the fetus for metabolic thrift, creating a mismatch in calorie-abundant adult environments
Implications for Screening and Prevention
Use ethnic-specific BMI cut-offs — 23 for overweight and 25 for obesity in South Asians, not 25 and 30
Measure waist circumference routinely — above 90 cm in men and 80 cm in women signals elevated metabolic risk