Structural equation model of determinants of adolescent body mass index

Adolescence is a critical developmental stage in which Body Mass Index (BMI) is a key indicator of nutritional and health status. In Nigeria, limited research has examined the behavioral, psychosocial, dietary, lifestyle, and socioeconomic factors influencing adolescent BMI within an integrated framework. This study applied Partial Least Squares Structural Equation Modeling (PLS-SEM) using secondary data from the 2018 Nigeria Demographic and Health Survey (NDHS) to investigate both direct and indirect determinants of adolescent BMI. Findings revealed that lifestyle factors were the only construct exerting a significant direct effect on BMI (β = 0.164, p < 0.001), underscoring the critical role of modifiable daily behaviors. Socioeconomic status (SES), while not directly associated with BMI, demonstrated significant indirect effects through its influence on behavioral patterns (β = −0.273, p = 0.006) and lifestyle (β = −0.289, p = 0.011). Other constructs, including dietary, psychosocial, physical activity, and health factors, did not yield significant direct effects. Despite these associations, the model's explanatory power was only moderate (R² = 49%), suggesting that unmeasured determinants, such as genetic, biological, and environmental influences, may account for more of the observed variation. The study concludes that adolescent BMI is multidimensional, with lifestyle factors playing a central role, while SES influences outcomes indirectly. It recommended refining measurement tools, expanding research frameworks to include biological and environmental markers, adopting longitudinal study designs, and strengthening methodological capacity in SEM to improve public health research and intervention strategies.