Immigrants to a new county are often healthier than those born in the host country, a phenomenon known as the immigrant health advantage. Yet, this advantage often erodes with time. For example, immigrants to the United States are less obese than their U.S. born counterparts, but the rates of obesity converge after 15 years. This erosion is often attributed to acculturation, referring to the immigrants adopting the behaviors of the host society. Yet, studies of acculturation are confounded by secular trends, an important one being the nutrition transition. This transition refers to the increasing availability of processed and fatty foods, and decline of nutritious foods in rapidly developing countries, and a corresponding rise in obesity. The nutrition transition raises the counterfactual of whether rates of obesity would rise over time among migrants if they had not left their home countries. In this presentation, we describe the design and rationale of the Health of Philippine Emigrants Study (HoPES). The baseline sample was collected in 2017 with follow-up through 2020. HoPES has several unique features that makes it well-suited to study the counterfactual. First, HoPES involves 2 cohorts: one cohort (n=832) migrates from the Philippines to the U.S. and another cohort (n=805) remains in the Philippines for the duration of the study. Second, the baseline data for both cohorts is obtained in the Philippines. Importantly, this provides us with novel pre-migration data for the immigrant cohort. Collectively, these features allow HoPES to approximate a natural experiment from which to directly study the effects of migration.