2 Public health need and practice
Between 2005 and 2008, 9.3% of all babies born in England were of South Asian origin (defined as 'Bangladeshi, Indian, Pakistani and any other Asian background' with the exception of Chinese people). A further 5.3% were of black family origin (defined as 'African, Caribbean and any other black background') (Office for National Statistics 2011a).
According to the 2011 census, 7.9 million people in the UK belonged to a black, Asian or other minority ethnic group, representing 14% of the total population (Office for National Statistics 2012). People of Indian family origin were the largest minority ethnic group, followed by people of Pakistani family origin, those of mixed ethnic family origin and people of black African, black Caribbean and Chinese family origin (Office for National Statistics 2011b).
In England and Wales, London was the most ethnically diverse area, with the highest proportion of minority ethnic groups and the lowest proportion of white population, at 59.8% (Office for National Statistics 2012).
According to the World Health Organization criteria, adults of white European origin with a BMI of 30 kg/m2 or more are described as obese. Those with a BMI from 25–29.9 kg/m2 are considered overweight.
A 'raised' waist circumference is defined as above 102 cm (40 inches) for men and above 88 cm (35 inches) for women. However, the International Diabetes Federation has suggested lower cut-off points (of 94 cm (37 inches) in men and 80 cm (31.5 inches) in women) for measuring metabolic syndrome (Alberti et al. 2005, 2007).
The BMI cut-off points identified above correspond to the risk of a range of chronic diseases and mortality among Europeans (World Health Organization 1998). However, these thresholds do not account for the wide variation in body fat distribution – and may not correspond to the same degree of associated health risk – for different ethnic groups (World Health Organization 2000).
A recent report stressed: 'there is no straightforward relationship between obesity and ethnicity, with a complex interplay of factors affecting health in minority ethnic communities in the UK'. It added that the validity of using current definitions of obesity for non-white minority ethnic groups is debatable (National Obesity Observatory 2011).
In response to a World Health Organization report (2004), the NHS Health Checks programme uses a BMI of 27.5 kg/m2 as the trigger for preventive action among people of South Asian origin. Obesity: the prevention, identification, assessment and management of overweight and obesity in adults and children (NICE clinical guideline 43) did not consider there to be sufficient evidence to set separate cut-off points for the BMI or waist circumference of this group. However, waist circumference cut-off points of ≥90 cm (35 inches) for men and ≥80cm (31.5 inches) for women for South Asian and Chinese populations have subsequently been proposed in the International Diabetes Federation (IDF) statement on type 2 diabetes prevention (Alberti et al. 2005, 2007).
The IDF proposal is in line with general World Health Organization (2004) guidance, which recognises the increased risk of type 2 diabetes and cardiovascular disease at a lower BMI among people from Asian populations, in comparison to people from white populations.
Excess body fat contributes to around 58% of cases of type 2 diabetes, 21% of heart disease and between 8% and 42% of certain cancers (breast, colon and endometrial) (DH 2003). However, the point at which the level of body fat becomes risky to health varies between ethnic groups.
In addition, the prevalence of some of these health conditions is far greater among black, Asian and other minority ethnic groups – despite the fact that rates of obesity among these groups are similar to (or lower than) the rate among the white population (World Health Organization 2004).
However, rates of myocardial infarctions are higher among South Asian groups at an earlier age – and death rates from cardiovascular disease are approximately 50% higher (Allender et al. 2007). In addition, the prevalence of diabetes is up to 6 times higher among South Asian groups, it tends to develop at a younger age and disease progression is faster (Khunti et al. 2009).
In the UK, people of black African and African-Caribbean origin are 3 times more likely to have type 2 diabetes than the white population (DH 2001). Type 2 diabetes is also more common among Chinese people (DH 2001). In addition, people from all of these groups are more at risk of stroke (National Obesity Observatory 2011).
Type 2 diabetes is also more prevalent among black Caribbean, Indian, Pakistani and Bangladeshi men aged 35–54 than the general UK population. With the exception of black African men, it is also more prevalent among those aged 55 and over from these groups (NHS Information Centre 2005).
Among women, type 2 diabetes is more common among Indian, Pakistani and Bangladeshi groups (aged 35 and over) and black Caribbeans (aged 55 and over) in the UK (NHS Information Centre 2005).
People from black, Asian and other minority ethnic groups also tend to progress from impaired glucose tolerance (IGT) to diabetes much more quickly than average (more than twice the rate of white populations) (Ramachandran et al. 2006).
Compared to white Europeans, people of South Asian origin living in England tend to have a higher percentage of body fat at a given BMI. They also tend to have more features of the metabolic syndrome at a given waist circumference (for example, higher triglycerides and lower high-density lipoproteins in women and higher serum glucose in men). (For details see Obesity: the prevention, identification, assessment and management of overweight and obesity in adults and children [NICE clinical guideline 43].)
It has been suggested that this increased risk may be due to South Asian people accumulating more fat in the abdomen and around the waist, compared to white European populations. Fat distributed in this region of the body is considered to be more metabolically active. It is also closely associated with insulin resistance, pre-diabetes and type 2 diabetes (Banerji et al. 1999; McKeigue et al. 1991, 1992, 1993).
 This relates to all South Asian and Chinese populations as described above plus other Asian populations for example Japanese, Korean, Indonesian, Filipino and Thai.