This paper reviews literature between 1974 and 2007 that addresses the impact of sociocultural factors on reported patterns of eating, physical activity (activity) and body size of Tongans and indigenous Fijians (Fijians) in their countries of origin. There have been changes in diet (more imported and fewer traditional foods), activity (reduced, especially in urban settings), residence (rural-urban shift) and body size (increased obesity and at a younger age). The prevalence of overweight/obesity in Tongans and Fijians has increased rapidly over the last two decades and remains among the highest in the world (>80% in Tonga; >40% in Fiji), with more females reported to be obese than males. The few studies that investigated sociocultural influences on patterns of eating, activity and/or body size in this population have examined the impact of hierarchical organisation, rank and status (sex, seniority), values (respect, care, co-operation) and/or role expectations. It is important to examine how sociocultural factors influence eating, activity and body size in order to i) establish factors that promote or protect against obesity, ii) inform culturally-appropriate interventions to promote healthy lifestyles and body size, and iii) halt the obesity epidemic, especially in cultural groups with a high prevalence of obesity. There is an urgent need for more systematic investigations of key sociocultural factors, whilst taking into account the complex interplay between sociocultural factors, behaviours and other influences (historical; socioeconomic; policy; external global influences; physical environment).