The metabolic syndrome in South Asians: epidemiology, determinants, and prevention.

BACKGROUND: The prevalence of obesity and the metabolic syndrome is rapidly increasing in India and other south Asian countries, leading to increased morbidity and mortality due to type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD).

METHODS: The literature search has been carried out using the key words "insulin resistance, the metabolic syndrome, cardiovascular risk, diabetes, obesity, Asian Indians, and South Asians" in the medical search engine Pubmed (National Library of Medicine, Bethesda, MD) from 1966 to September 2009.

RESULTS: A high prevalence of the metabolic syndrome and associated cardiovascular risk factors has been observed not only in urban South Asian/Asian Indian adults and children but also in economically disadvantaged people residing in urban slums and rural areas. The main drivers are rapid nutrition, lifestyle, and socioeconomic transitions, consequent to increasing affluence, urbanization, mechanization, and rural-to-urban migration. Less investigated determinants of the metabolic syndrome include psychological stress in urban setting, genetic predisposition, adverse perinatal environment, and childhood "catch up" obesity. Data show atherogenic dyslipidemia, glucose intolerance, thrombotic tendency, subclinical inflammation, and endothelial dysfunction are higher in South Asians than Caucasians. Many of these manifestations are more severe and are seen at an early age (childhood) in South Asians than Caucasians. Metabolic syndrome and cardiovascular risk in South Asians is also heightened by their higher body fat, truncal subcutaneous fat, intra-abdominal fat, and ectopic fat deposition (liver fat, etc.). Further, cardiovascular risk cluster manifests at a lower level of adiposity and abdominal obesity. The cutoffs of body mass index and waist circumference for defining obesity and abdominal obesity, respectively, have been lowered and the definition of the metabolic syndrome has been revised for Asian Indians in a recent consensus statement, so that physicians could intervene early with lifestyle management. Data from a major intervention program conducted by us on urban adolescent schoolchildren in north India for prevention of obesity (the MARG project) has shown encouraging results, making it a model for any future intervention program in South Asians.

CONCLUSIONS: Cardiometabolic risk is high in South Asians, starting at an early age. Increasing awareness of cluster of risk factors and how to prevent them should be emphasized in population-wide prevention strategies in South Asian countries, primarily focusing on children.