OBJECTIVE This review examines the risk of obesity in migrant groups-specifically migrants from countries with lower prevalence of obesity to countries with higher prevalence of obesity. We examine obesity prevalence within migrant groups compared with native populations and the evidence on factors that might shape obesity risk in these migrant groups. RESULTS Migrants may arrive in new countries with a health advantage including generally a healthier body weight. Genetic and epi-genetic factors, as well as body size preference, socio-economic factors, and stress exposure, may play a role in increasing unhealthy weight gain in migrant populations. This unhealthy weight gain leads to similar or greater obesity risk in migrant populations compared with native populations 10-15 years after migration. Meeting the challenge of prevention and treatment of obesity in diverse populations will require greater attention to minority groups in research in the future.