The Republic of Vanuatu, similar to other South Pacific island nations, is undergoing a rapid health transition as a consequence of modernization. The pace of modernization is uneven across Vanuatu's 63 inhabited islands, resulting in differential impacts on overall body composition and prevalence of obesity among islands, and between men and women. In this study, we investigated (1) how modernization impacts body composition between adult male and female Melanesians living on four islands of varying economic development in Vanuatu, and (2) how body composition differs between adult Melanesians and Polynesians living on rural islands in Vanuatu.