Why South Asians Have More Fat Deposits
South Asians have inherently higher body fat percentages and preferential visceral fat accumulation at any given BMI compared to other ethnic groups due to genetic predisposition, altered body composition with lower muscle mass, and metabolic differences that manifest even in lean individuals. 1, 2
Body Composition Differences
South Asians demonstrate a distinct "high body fat-normal BMI-low muscle mass" phenotype that fundamentally differs from other populations 3:
- For the same BMI, South Asians have 2-3 kg/m² more body fat than Caucasians, meaning a "normal weight" South Asian carries significantly more adipose tissue than their Caucasian counterpart 2, 4
- Despite lower BMI values, South Asians have less total lean abdominal muscle mass compared to all other racial/ethnic groups 1, 2
- South Asian Canadians showed higher body fat percentage and waist-to-hip ratios compared to white Canadians at similar BMIs 1
Fat Distribution Pattern
The distribution of fat in South Asians is particularly problematic from a metabolic standpoint 1:
- South Asians accumulate more visceral and deep subcutaneous fat compared to superficial subcutaneous fat 1
- Mean total abdominal adipose tissue is higher in South Asian men compared to non-Hispanic white men 1
- Excessive ectopic fat deposition occurs in the liver (non-alcoholic fatty liver disease), pancreas, and skeletal muscle 5, 6, 3
- This preferential visceral adipose tissue accumulation occurs even at lower BMI levels 2, 6
Metabolic Alterations
South Asians exhibit metabolic dysfunction that predisposes to fat accumulation 1:
- Higher fasting insulin levels and greater insulin resistance despite similar or lower BMI values compared to non-Hispanic whites 1, 2
- Insulin resistance is evident at the cellular and physiological levels even in lean South Asian individuals 2, 5
- Lower adiponectin levels (independently of insulin resistance) in South Asian women compared to non-Hispanic white women 1
- Higher plasma leptin levels in South Asian young adults compared to those of European descent 1
- Lower IGFBP-1 (insulin-like growth factor-binding protein) levels 1
Underlying Mechanisms
The reasons for increased fat deposits are multifactorial 5, 7, 8:
- Genetic predisposition with ancestral variations in feast-and-famine cycles that created inherited tendencies toward fat storage 7, 8
- Gene-environment interactions where genetic predispositions are amplified by modern lifestyle factors 7, 8
- Adverse perinatal environment and childhood "catch up" obesity contributing to metabolic programming 8
- Rapid nutrition and lifestyle transitions with high intakes of refined carbohydrates and saturated fats combined with inadequate physical activity 5, 6, 8
Clinical Implications
These body composition differences necessitate different diagnostic thresholds 1, 2, 4:
- The World Health Organization and American Diabetes Association recommend BMI ≥23 kg/m² for overweight and ≥25 kg/m² for obesity in South Asians (not the standard 25 and 30 kg/m²) 1, 2, 4
- Waist circumference thresholds are ≥90 cm for South Asian men and ≥80 cm for South Asian women 2, 4
- Metabolic complications develop at BMI levels considered "normal" by Western standards 2, 3
Important Caveats
- Migrants from South Asia have higher BMIs compared to South Asians who remained in their native country, suggesting environmental factors amplify genetic predisposition 1
- BMI is a weak risk factor for CVD mortality in South Asians, making waist-to-hip ratio and waist circumference more clinically relevant measures 1
- These metabolic alterations are evident in young South Asian adults, highlighting the need for early intervention starting in childhood 1, 8