Background: Virtually all strategies for managing population increases in obesity prevalence include recommendations for increasing moderate-to-vigorous physical activity (MVPA), despite lack of consensus in the scientific community. Modeling the Epidemiologic Transition Study (METS), a prospective cohort study, previously found no association between objectively measured MVPA or sedentary behavior and weight change in adults from 5 countries after two years of follow-up. We are now able to assess these associations among Seychellois women after an additional 3 years of follow-up (men’s data being entered). Methods: At baseline, METS recruited 500 adults, 25-45 years old, in each country and conducted annual follow-up examinations. Measurements included anthropometrics and PA using accelerometry. In Seychelles, 270 women were enrolled at baseline and 220 examined at year 5 (81.5% retention); 194 women with complete data were included in analyses. Univariate and multivariate analyses were used to determine associations between MVPA (minutes/day) and sedentary behavior (minutes/day), and weight change over 5 years. Results: Mean (± SD) weight was 71.9 ± 17.2 kg at baseline; mean total weight change was 5.4 ± 6.6 kg (range, -26.4 to +27.0 kg). Univariate analyses found no significant association between either MVPA or sedentary time and 5-year weight change (all p>0.05). Multivariate analysis, controlling for age and baseline weight, did not alter the outcomes. Conclusions: These prospective data do not support the recommendation that volume of MVPA or sedentary behavior will moderate weight over time. Understanding the etiology of excess weight gain and obesity is critical for developing evidence-based public health policies.