Background Previous research has identified ethnic differences in abdominal obesity but has not fully explored the pathways that explain these ethnic differences, which may relate to individual and contextual characteristics. This research identifies ethnic differences in waist circumference for eight ethnic groups in England, before and after accounting for a range of individual-level and area-level factors. Three key pathways to obesity are explored: migration, culture, and socio-economic characteristics.

Methods Data come from four years of the Health Survey for England (1998, 1999, 2003 and 2004) and linked area-level data from the 2001 Census. The total sample size is 27,946. Multi-level modelling methods are used to account for individual-level and area-level factors. The main outcome measure is objectively measured waist circumference. Area-level variables are Index of Multiple Deprivation and Co-ethnic density.

Results The results show that migration to the UK has a strong association with ethnic differences in waist circumference – in particular, waist circumference increases with length of time since migration to the UK. Cultural characteristics and socio-economic characteristics are also associated with ethnic differences in waist circumference, but not to the same extent as migration. The strong association between migration and waist circumference is partly attenuated by cultural characteristics and partly by socio-economic inequality. However, there is still a large association between migrant status and waist circumference that remains unexplained. Area deprivation has an association with ethnic differences in obesity.

Conclusion This research makes an important contribution to the study of ethnic differences in waist circumference in England. It is the first UK study to explore the associations of migration, cultural and socio-economic pathways with ethnic differences in waist circumference for a wide range of ethnic groups, using both individual and contextual data. The resultsillustrate the multi-dimensional nature of ethnic inequalities in obesity and the complex interplay between migration, culture and socio-economic inequality. Policy makers should focus on obesity prevention among child and adult migrants, particularly focussing on length of time since migration, the removal of barriers to educational attainment and employment among migrant populations and the effect of the areas that migrants live, particularly in relation to area deprivation. Obesity is an important factor in many health-related outcomes so the regular tracking of ethnic inequalities in obesity and a clear understanding of the pathways behind these differences is fundamental for improving the health of ethnic minority people.