Association of socioeconomic status with BMI differs by sex and position on BMI distribution among participants in the Cebu Longitudinal Health and Nutrition Survey (CLHNS)

To assess the association of variables representing the nutrition transition with BMI among young adults in a dynamic urbanising area in the Philippines; to test whether the roles of these variables were constant across the BMI distribution; and whether these patterns differed by sex. Data from the Cebu Longitudinal Health and Nutrition Survey rounds in 2002 (n = 1940), 2005 (n = 1802), 2009 (n = 1621), and 2018 (n = 1267) were used to assess BMI among young adults (ages 21–35 years). Main exposures included socioeconomic status (SES) represented by a lagged household asset index and urbanicity, and current education level. Models were stratified by sex and adjusted for employment status and parity in females. Quantile regression was used to examine the relationship between these variables and BMI. Household asset index was highly correlated with male BMI, its coefficient increasing from 2005 to 2018 and differing between quantiles; its association with female BMI was only positive among parous women whose BMI was at 0.50 and 0.75 quantiles in 2005. We found no associations between urbanicity and BMI in males, but negative and positive associations at 0.25 and 0.75 quantiles in females in 2018, respectively. College education was negatively associated with BMI in females, with larger effect sizes at 0.75 quantile, but positively in males at 0.25 and 0.50 quantiles in 2018. Associations of SES-related variables with BMI vary along BMI distribution and differ among male and female young adults in Cebu, Philippines. Males exhibit a pattern more characteristic of lower- or middle-income country (LMIC) settings than females, whose trends are more akin to those observed in high-income countries (HICs). Results will inform a more detailed inquiry into more proximal factors determining BMI.