Association between prenatal, pre-pregnancy rainfall and adult obesity: Findings from the Community Behavior and Attitude Survey in Tuvalu (COMBAT)

Background: Tuvalu has one of the highest obesity prevalence, which faces a major public health challenge with limited resource. Early-life environmental factors, such as altered rainfall patterns, may increase obesity risk. This study examined the association between prenatal rainfall exposure and adult obesity to inform obesity prevention in climate-vulnerable populations. Methods: A nationwide survey was conducted between February and May 2022, which included 892 adults from Tuvalu. Rainfall data was obtained from ECMWF Reanalysis v5 based on participants’ birth year and birthplace. Rainfall exposure during the first year of birth, the year before birth, and two years before birth was analyzed, and rainfall exposure between three to five years before birth were analyzed as negative control periods. Obesity and severe obesity were defined based on body mass index (BMI) upon the survey, according to the World Health Organization criteria. Results: The results showed associations between higher rainfall during the year and two years before birth, increased BMI and greater odds of adulthood obesity. These associations were more pronounced among male participants. No significant associations were observed for rainfall three to five years before birth. Conclusions: Prenatal exposure to higher rainfall during prenatal and pre-pregnancy periods are associated with increased obesity risk in adulthood, reflecting prenatal environmental influences on developmental periods. These findings emphasize the importance of understanding climate-related health exposures and the need for targeted interventions in climate change-vulnerable populations. Further research can extend to other Pacific Island nations and identify mechanisms linking rainfall, birth weight, and obesity.