Obesity-related non-communicable diseases: South Asians vs White Caucasians

International Journal of Obesity (2011) 35, 167–187 & 2011 Macmillan Publishers Limited All rights reserved 0307-0565/11 www.nature.com/ijo REVIEW Obesity-related non-communicable diseases: South Asians vs White Caucasians A Misra1,2,3 and L Khurana1,2 1 National Diabetes, Obesity, and Cholesterol Disorders Foundation (N-DOC), New Delhi, India; 2Diabetes Foundation (India), New Delhi, India and 3Department of Diabetes and Metabolic Diseases, Fortis Hospital, Vasant Kunj, New Delhi, India South Asians are at higher risk than White Caucasians for the development of obesity and obesity-related non-communicable diseases (OR-NCDs), including insulin resistance, the metabolic syndrome, type 2 diabetes mellitus (T2DM) and coronary heart disease (CHD). Rapid nutrition and lifestyle transitions have contributed to acceleration of OR-NCDs in South Asians. Differences in determinants and associated factors for OR-NCDs between South Asians and White Caucasians include body phenotype (high body fat, high truncal, subcutaneous and intra-abdominal fat, and low muscle mass), biochemical parameters (hyperinsulinemia, hyperglycemia, dyslipidemia, hyperleptinemia, low levels of adiponectin and high levels of C-reactive protein), procoagulant state and endothelial dysfunction. Higher prevalence, earlier onset and increased complications of T2DM and CHD are often seen at lower levels of body mass index (BMI) and waist circumference (WC) in South Asians than White Caucasians. In view of these data, lower cut-offs for obesity and abdominal obesity have been advocated for Asian Indians (BMI; overweight 423 to 24.9 kg m2 and obesity X25 kg m2; and WC; men X 90 cm and women X80 cm, respectively). Imbalanced nutrition, physical inactivity, perinatal adverse events and genetic differences are also important contributory factors. Other differences between South Asians and White Caucasians include lower disease awareness and health-seeking behavior, delayed diagnosis due to atypical presentation and language barriers, and religious and sociocultural factors. All these factors result in poorer prevention, less aggressive therapy, poorer response to medical and surgical interventions, and higher morbidity and mortality in the former. Finally, differences in response to pharmacological agents may exist between South Asians and White Caucasians, although these have been inadequately studied. In view of these data, prevention and management strategies should be more aggressive for South Asians for more positive health outcomes. Finally, lower cut-offs of obesity and abdominal obesity for South Asians are expected to help physicians in better and more effective prevention of OR-NCDs. International Journal of Obesity (2011) 35, 167–187; doi:10.1038/ijo.2010.135; published online 20 July 2010 Keywords: diabetes; coronary heart disease; South Asians; White Caucasians Introduction South Asian countries are experiencing a rapid increase in obesity-related non-communicable diseases (OR-NCDs), including type 2 diabetes mellitus (T2DM), hypertension, dyslipidemia and coronary heart disease (CHD).1–4 Insulin resistance and clustering of proatherogenic, cardiovascular risk factors (the metabolic syndrome) are frequently seen in South Asians, even at a young age.5–7 Increasing trend of obesity, both in adults and children, is directly responsible for rapid increase in NCDs.7–12 Correspondence: Dr A Misra, Department of Diabetes and Metabolic Diseases, Fortis Flt. Lt. Rajan Dhall Hospital, Vasant Kunj, New Delhi 110070, India. E-mail: Received 17 January 2010; revised 1 June 2010; accepted 6 June 2010; published online 20 July 2010 It has increasingly become apparent that South Asians have a higher risk of NCDs compared with White Caucasians, which may be contributed by a number of factors, discussed subsequently.13–16 Early onset and heightened risk of OR-NCDs in South Asians as compared with White Caucasians have important implications for prevention and therapy. An understanding of the different mechanisms and factors responsible for increased susceptibility and different outcomes of OR-NCDs would give physicians and scientists a better insight in research and management of these chronic diseases in South Asians.8,11 This would also be in line with the global strategy of WHO (World Health Organization) to reduce the burden of NCDs through integrated prevention/ control of risk factors at individual, family, community and population levels.17 In this review, we attempt to analyze the evidence, possible mechanisms and determinants responsible for increased OR-NCDs in South Asians versus White Caucasians A Misra and L Khurana 168 tendency of OR-NCDs, as well as discuss management issues, in South Asians, as compared with White Caucasians, and also other ethnic groups. Definition of ‘White Caucasians’ and ‘South Asians’ Natives of first or subsequent generation immigrants originating from the Indian subcontinent (India, Pakistan, Bangladesh, Nepal and Sri Lanka) are referred to as ‘South Asians’. For this ethnic group, ‘Indo-Asians’ has also been used by various authors. ‘White Caucasians’ (henceforth referred as ‘Whites’ in the text) are defined as native Europeans/European immigrants, as well as indigenous White individuals in any other country. However, some studies have not referred ‘Caucasians’ as Whites (though probably implied), and the term ‘Caucasians’ has been used as such there. The term ‘Europeans’ has been retained wherever referred to in the original text. Methodology for literature search The literature search has been performed using the key words ‘obesity, insulin resistance, diabetes, hypertension, the metabolic syndrome, cardiovascular risk, coronary artery disease, Asian Indians, South Asians, Indo-Asians, Whites, Caucasians, White Caucasians and Europeans’ from medical search engine Pubmed (National Library of Medicine, Bethesda, MD, USA) from 1966 to December 2009. Manual search for other important references, and medical databases were also performed. Well-designed studies and those published in high impact journals were given preference for citation. Increasing OR-NCDs in South Asians: lifestyle-driven and multi-factorial origin Increasing OR-NCDs, including T2DM, hypertension, dyslipidemia and CHD, are seen in urban and even rural South Asian populations due to several reasons, such as increasing urbanization, rural-to-urban migration, mechanization and increased life expectancy (‘epidemiological transition’), ‘westernized lifestyle’ (high carbohydrate, high-fat, low-fiber diet with decreasing trends in physical activity; ‘nutrition and lifestyle transitions’).11,18–28 2010 and 79.4 million in 2030.29–33 Increasing trend in Asian Indians living in India is more apparent in urban populations (exponential trend R2 ¼ 0.744) than rural populations (R2 ¼ 00.289).34 Although the prevalence of diabetes was reported to be 12–14% in urban India, the rural population showed a relatively (...truncated)