Multidimensional Determinants of Obesity: The Role of Life Purpose, Sociodemographics, and Health Habits Across Four Adiposity Scales in a Large Occupational Cohort

<b>Background:</b> Obesity is multifactorial, shaped by biological, behavioral, and psychosocial factors. Traditional sociodemographic and lifestyle influences are well studied, but psychological well-being, particularly life purpose, remains less explored. This study investigates associations between demographics, health behaviors, and life purpose and obesity prevalence, assessed through four validated adiposity indices in Spanish workers. <b>Methods:</b> This cross-sectional study included 93,077 workers (mean age: 43.8 ± 9.6 years; 54.1% men). Obesity was defined according to four measures: body mass index (BMI), waist-to-height ratio (WtHR), Clínica Universidad de Navarra Body Adiposity Estimator (CUN-BAE), and Metabolic Score for Visceral Fat (METS-VF). Sociodemographic, lifestyle (Mediterranean diet, physical activity, smoking), and psychological (Purpose in Life Test, PIL-10) variables were assessed. Logistic regression was used to evaluate associations with obesity risk. <b>Results:</b> Low life purpose was significantly associated with increased odds of obesity across all indices, particularly for CUN-BAE (OR = 4.58; 95% CI: 3.99-6.28) and BMI (OR = 5.45; 95% CI: 4.71-6.30). Traditional risk factors such as physical inactivity, poor adherence to the Mediterranean diet, older age, a lower social class, and smoking also demonstrated strong associations with higher adiposity levels. METS-VF showed the greatest sensitivity to male sex and unhealthy behaviors. <b>Conclusions:</b> This study identifies life purpose as an independent psychosocial determinant of obesity. Using multiple adiposity measures strengthens the findings, emphasizing psychological well-being in prevention. Longitudinal research is needed to confirm causality and develop interventions enhancing life purpose to improve cardiometabolic health. Given the cross-sectional design, causal inferences cannot be drawn and the directionality of associations remains uncertain.