According to the World Health Organization (WHO), non-communicable chronic diseases (NCDs) such as cardiovascular disease, cancer, chronic respiratory disease and diabetes cause 60% of all deaths globally [1]. By 2030, the global cost of NCDs will reach $47 trillion [2]. Moreover, 80% of this mortality occurs in low- and middle-income countries [1]. Numerous studies have shown that South Asian populations (e.g. India, Pakistan, Bangladesh, Sri Lanka, and Nepal) contribute the highest proportion of the global burden of cardiovascular diseases [3,4]. In addition, risk factors for NCDs such as central obesity, hypertension and insulin resistance develop at a lower age in South Asians than other ethnic groups [5,6]. Moreover, South Asian immigrants overseas have a three to five-fold increase in the risk for myocardial infarction and cardiovascular death compared with other ethnic groups [7,8].

Obesity is a major contributor to cardiovascular disease and hence, it is a leading risk factor for adult mortality in both developed and developing countries [9]. People from Asia have a higher risk of type 2 diabetes and cardiovascular disease at lower levels of body mass index (BMI) [10]. Thus, in South Asians migrants, substantially lower obesity levels show an equivalent amount of dyslipidemia and dysglycemia when compared to BMI-matched White Europeans [11]. Furthermore, immigrant populations relocating from low- and medium-income countries to a higher income country are at a greater risk of weight gain, particularly males [12]. The ‘Healthy Migrant Effect’ is a phenomenon observed in epidemiology where newly arrived migrants tend to be healthier than the host population due to a positive selection bias that a formal migration process and residency health checks require. Emerging evidence suggests that the ‘Healthy Migrant Effect’ may diminish with increased years of residency due to lifestyle and nutrition transition associated with acculturation i.e. the complex, gradual exchange of immigrants’ original attitudes and behaviours to the obesogenic behaviours in the host culture. A recent systematic review synthesised data from nine cross-sectional studies of Mexican, El Salvador, Puerto Rico, Thailand/Laos Hmong, Korean and Soviet Union immigrants residing in the United States. Findings showed a positive association between higher acculturation and body mass index in males [12].

In the past 40 years, the United Arab Emirates (UAE) has achieved significant economic and industrial growth. The rising affluence of the UAE population with its accompanying increased caloric intake, and decreased physical activity has rapidly increased the prevalence of obesity [13,14]. Consequently, the UAE ranks sixth in a recent indexing of the top 10 ‘heaviest’ countries in the world (ranking determined by number of adults per tonne of human biomass) [15]. The expatriate population accounts for approximately 89 percent of UAE population and approximately two-thirds of all the immigrants are South Asian [16]. The UAE population has increased substantially over the past four decades and this is primarily due to the high net inward migration of expatriate workers from South Asia (UAE population estimates: 287,000 in 1971, 4.1 million in 2005, 8.3 million in 2010). Abu Dhabi is the largest of the seven UAE emirates with an estimated population of 2.3 million, of which over half of the population are expatriate males aged 20-59 years. All expatriate workers seeking employment in the UAE are required by federal law to undergo a health and communicable disease screening test at a government visa screening centre before receiving a residency permit. In 2012, 181,231 male immigrants visited the visa screening centre (Disease Prevention and Screening Centre, Preventive Medicine Department, Health Authority Abu Dhabi) in the city of Al Ain (second largest city in Abu Dhabi Emirate) to obtain or renew a visa [17]. Majority of these workers are low-paid, semi- or unskilled, without long-term job security, living alone or in shared accommodation, and separated from their families, they often suffer from stress, anxiety and depression [18]. A dearth of information exists on the prevalence of overweight and obesity among South Asian immigrants in the UAE. The aim of this study was to assess the prevalence of obesity and explore the relationship between years of residency (surrogate measure for acculturation) and obesity among South Asian (from India, Pakistan and Bangladesh) male immigrants residing in the UAE.

A higher proportion of Bangladeshi subjects (23.2%) reported a family history of hypertension compared to Indians (14.8%) and Pakistanis (15.0%). A family history of diabetes was significantly more prevalent among Indians (15.9%) compared to Pakistanis (8.1%) and Bangladeshi (8.9%) participants. Indians had a higher mean BMI (31.5 kg/m²) compared to Pakistanis (26.6 kg/m²) and Bangladeshis (26.2 kg/m²). Bangladeshis had lower waist circumference (85.6 cm) and waist-to-hip ratio (0.92 cm) but reported a high rate of smoking (49.1%) as compared to their Indian (34.3%) and Pakistani (35.8%) counterparts. Overall, 9.0% of the sub-sample (n = 99) were diabetic (HbA1c ≥6.5%) and most of these reported having a physician diagnosis of diabetes. The prevalence of hypertension was 30.5% despite this being a young population of South Asian males. Nearly two-thirds (61.6%) of the sample reported that they had never had their blood pressure measured. Among the study population, 44.4% of participants with diabetes and 76.0% of those with hypertension were not aware of their status. Overall a small proportion of the study participants reported moderate 26.7% (95% CI 24.4 - 29.1) and vigorous, 18.2% (95% CI 16.1 - 20.2) physical activity. Self-reported vigorous and moderate physical activity was particularly low among drivers (13.6%, 14.2%), shopkeepers and business men (13.3%, 15.0%), and tailors (4.3%, 7.1%).

The overall crude prevalence of overweight and obesity in South Asian immigrants were 35.4% (95% CI 32.8%, 37.9%), and 9.4% (95% CI 9.2%, 9.5%), respectively. The crude prevalence of central obesity was 63.4% (95% CI 60.8%, 65.9%). The crude prevalence of overweight and obesity was highest among Pakistanis, 52.5% (95% CI 47.3%, 57.5%), followed by Indians, 47.4% (95% CI 42.7%, 52.2%) and Bangladeshis, 37.4% (95% CI 33.4%, 41.6%). The overall crude prevalence of central obesity varied by nationality, 66.7% (95% CI 62.8%, 71.1%) in Indians, 64.7% (95% CI 59.7%, 69.5%) in Pakistanis, and 59.9% (95% CI 55.7%, 64.0%) in Bangladeshis.

Figure 1 illustrates the prevalence of underweight, normal weight, overweight and obesity by the duration of residency in South Asian immigrants. The prevalence of underweight decreased from 8% among those who had been in UAE for up to five years, to 1% among those who had been in UAE for more than 10 years. Prevalence of overweight and obesity was significantly (p < 0.05) higher (62%) among those who had been in UAE for more than 10 years.

We did not find a significant (p < 0.05) association of hypertension and cigarette smoking with living in the UAE for 6 to 10 years or more than 10 years. Diabetes was significantly associated with 10 or more years of residency in UAE. We did not find a significant relation of other lifestyle variables such as physical activity with duration of residency in UAE.

The prevalence of overweight and obesity in our sample of South Asian immigrants living in the UAE was higher than published estimates from their home countries of India, Pakistan and Bangladesh. The mean BMI in our study was considerably higher compared to working men aged 20 to 59 years in India (31.5 kg/m² versus 23.1 kg/m²) [25] and Bangladesh (26.2 kg/m² versus 19.7 kg/m²) [26]. Prevalence of overweight and obesity in Pakistani immigrants was more than double compared to their counterparts in Pakistan (50.5% versus 22.0%) [27]. While the prevalence of overweight and obesity among South Asian immigrants living in UAE for more than 10 years (62.7%) was substantially higher than the prevalence amongst their own non-migrant countrymen, obesity was relatively close to age-standardised prevalence rate for the native Emirati population (67.7%) [28].

The prevalence of central obesity (63.4%) in the study sample was higher compared to native Emirati men (58.6%) [28], which is similar to results from other studies reporting high rates of central obesity (classified using the waist-to-hip ratio) among South Asian immigrants [28,29]. Central obesity is an independent risk factor for cardiovascular disease in the Indian subcontinent male population [30]; this highlights the importance of measuring central obesity rather than body mass and height alone.

In our study population, the prevalence of overweight and obesity was significantly higher among those who had been living in the UAE for a longer period. Indeed, the prevalence of overweight and obesity increased from 34.8% with five years residency to 59.3% with 6 to 10 years residency and 62.3% with more than 10 years of residency. Previous studies indicate relatively lower rates of poor health among newly arrived South Asian immigrants in Europe and Canada compared to the general population [31]. However, it would appear that that this “immigrant health advantage” over the native population will decrease as the number of years lived in the host country rises [32,33]. Significant changes in diet amongst immigrants have been reported, with a substantial increase in overall energy and fat intake due to the accessibility and availability of energy-dense foods and snacks. Moreover, there is a switch from whole grains and pulses to more refined sources of carbohydrate along with increased consumption of soft drinks [32]. Our results are consistent with previous studies in which long-term immigrants reported higher rates of obesity, diabetes, hypertension and smoking compared to natives [34]. Study findings provide more evidence on the notion of a Healthy Migrant Effect seen in Western countries where upon arrival, immigrants are healthier than the native population, however, their health status declines as the duration of their stay increases [31,32,34]. The UAE has been previously defined as an obesogenic environment due to an accelerated nutrition transition moving away from traditional “healthy” foods and a high level of physical activity to an abundance of “unhealthy” energy-dense foods coupled with a sedentary life style [13]. The prolonged positive energy balance required to elicit high rates of obesity among South Asian immigrant males living in the UAE for five or more years may be due to dietary acculturation characterized by adopting affordable low quality food with high energy intake (primarily from refined sugar and saturated fat) with or without a concomitant reduction in daily energy expenditure (physical activity). It might be the reason for a positive association between diabetes and living in UAE for more than ten years.

Drivers, shopkeepers and tailors reported very low levels of moderate and vigorous physical activity. The prevalence of BMI-derived overweight and obesity, and central obesity estimates was very high among migrants working in sedentary occupations such as drivers, shop keepers and tailors, particularly those who had lived in the UAE for more than five years. These findings are in agreement with other studies that have reported low physical activity and high engagement in sedentary behaviour among South Asian immigrants [35].

There was a significant positive significant association between obesity and college or university level education. The direct association between income and education in developed countries may indicate healthier lifestyle choices in those with higher literacy, particularly those with higher health literacy [36]. Further research is needed to elucidate whether this discrepancy may be due to factors such as poorer health literacy level [37].

An alarming finding is that almost 76% of study participants with hypertension and 44% with diabetes were not aware of their conditions. Compared to white Caucasians, South Asians report overall lower disease awareness: language barriers, religious and sociocultural factors have been attributed to poor awareness and late diagnosis [37,38]. Therefore, the treatment and control of hypertension and diabetes is crucial for reducing cardiovascular death rates as the study population is already prone to developing coronary heart disease at a younger age (<40 years in men) [5,6,8]. Greater emphasis on improving primary health care and health education in this population may increase awareness and promote healthy lifestyles has the potential to improve cardiovascular health.

This is the first study to reveal a high prevalence of overweight, obesity, hypertension and diabetes among a relatively young South Asian male immigrant population living in the UAE. Study findings suggest a diminished ‘Healthy Migrant Effect’ with increased years of residency possibly due to greater acculturation (particularly greater than five years residency) and a transition in lifestyle behaviors. Preventive health measures are often ignored in this population. Culturally-tailored health education interventions targeting the maintenance of a healthy body size, coupled with regular assessments of glucose control and blood pressure are urgently required in this population. The design, development, and implementation of future health promotion campaigns, interventions, and strategies amongst South Asians must consider the sociocultural, religious, ethnic, and educational diversity of this population.