Background: The aim of the study was to develop a research instrument to study the levels of health literacy for obesity prevention (HLFOP), as well as health behavior for obesity prevention (HBFOP). In addition, we investigated the causal relationship model between health literacy and health behavior for obesity prevention among primary school students in Bangkok, Thailand. Methods: A cross-sectional study among 600 participants who were primary school students (aged 9-13 years) was conducted. The participants were selected from schools in all parts of Bangkok using multi-stage random sampling technique. The research instrument to assess HLFOP and HBFOP, constructed by the researchers, were utilized for data collection. Data were analyzed using descriptive statistics, exploratory and confirmatory factor analyses, and structural equation model through linear structural relationship. Results: We found that HBFOP was directly influenced by heath literacy in the category of Critical Literacy with an effect size of 0.65 (p < 0.01), and was indirectly influenced in the category of Basic Literacy and Interactive Literacy through Critical Literacy with effect sizes of 0.46 and 0.58 (p Conclusions: HLFOP was influential on HBFOP in primary school students in the Bangkok Metropolis. The categories that were particularly influential were: 1) Basic Literacy: accessing health information skills; 2) Interactive Literacy: communication skills; and 3) Critical Literacy: media literacy and self-management skills.
