Educational Inequalities and Obesity: Association and Attenuation After Lifestyle Adjustment in a Cross-Sectional Working-Age Population

Background: Obesity is a major public health concern and shows a clear social gradient, with higher prevalence among individuals with lower socioeconomic position. Educational level is a key indicator of socioeconomic status, but the extent to which lifestyle factors explain its association with obesity remains unclear. Objective: To examine the association between educational level and obesity in a working-age population and to evaluate how adjustment for lifestyle factors influences the magnitude of the association between educational level and obesity. Methods: A cross-sectional study was conducted among 3108 working-age adults undergoing occupational health assessments in Spain. Educational level was categorised into three groups (higher, intermediate, and primary or none). Obesity was defined as a body mass index ≥30 kg/m2. Lifestyle variables included smoking status, physical activity assessed using the International Physical Activity Questionnaire (IPAQ-SF), and adherence to the Mediterranean diet evaluated with the MEDAS-14 score. Sequential logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (95% CI), with progressive adjustment for demographic, behavioural, and clinical factors. Results: The overall prevalence of obesity was 16.6%, with a clear gradient across educational levels (11.5% in higher education vs. 19.8% in primary or no education). In crude analyses, individuals with the lowest educational level had higher odds of obesity (OR 1.89; 95% CI 1.46–2.45). Adjustment for age and sex attenuated the association (OR 1.72; 95% CI 1.32–2.24), with further reduction after inclusion of lifestyle factors (OR 1.63; 95% CI 1.24–2.13). In the fully adjusted model, the association remained statistically significant (OR 1.61; 95% CI 1.18–2.21), indicating that adjustment for lifestyle factors attenuated the association between educational level and obesity, although the association remained statistically significant. Conclusions: Lower educational level is associated with a higher risk of obesity. Adjustment for lifestyle factors attenuated this association, although a statistically significant relationship remained. These findings support the role of education as a fundamental determinant of health and highlight the need for strategies addressing broader social and structural determinants of obesity.