Associations of Sociodemographic Factors, Lifestyle Habits, and Insomnia Severity with Obesity Indices in Spanish Workers: Sex-Specific Differences

<b>Background:</b> Obesity and insomnia are prevalent public health issues with shared behavioral and physiological pathways. However, their interplay remains understudied in occupational cohorts. Obesity and insomnia are prevalent public health issues with shared behavioral and physiological pathways. However, their interplay remains understudied in occupational cohorts. This study aimed to evaluate the associations of sociodemographic factors, lifestyle habits, and insomnia severity with multiple obesity indices in a large population of Spanish workers. <b>Methods:</b> We conducted a cross-sectional analysis of 84,898 workers (2021-2024). Data were obtained from annual occupational health assessments conducted across multiple Spanish regions between 2020 and 2024. Insomnia severity was assessed using the Insomnia Severity Index (ISI), dietary quality using the 14-item Mediterranean Diet Adherence Screener (MEDAS-14), and physical activity using the International Physical Activity Questionnaire-Short Form (IPAQ-SF). Adiposity was measured using Body Mass Index (BMI), waist-to-height ratio (WtHR), the Clínica Universidad de Navarra-Body Adiposity Estimator (CUN-BAE), and the Metabolic Score for Visceral Fat (METS-VF). Multivariable logistic regression models were used to examine associations adjusted for age, sex, education, and occupational social class. <b>Results:</b> Higher ISI scores were significantly and independently associated with elevated adiposity across all indices, with the strongest association observed for METS-VF (odds ratio = 1.19, 95% CI 1.14-1.25, <i>p</i> < 0.001). Women showed higher mean CUN-BAE and METS-VF values than men (CUN-BAE: 37.4 ± 6.2 vs. 25.6 ± 6.4; <i>p</i> < 0.001; METS-VF: 5.7 ± 0.7 vs. 6.4 ± 0.6; <i>p</i> < 0.001), despite lower BMI (25.3 ± 4.8 vs. 26.8 ± 4.3; <i>p</i> < 0.001). Lower physical activity (OR = 5.70; 95% CI 4.91-6.50), poor adherence to the Mediterranean diet (OR = 3.29; 95% CI 2.88-3.70), smoking (OR = 1.29; 95% CI 1.22-1.36), and lower occupational class (Class III: OR = 1.77; 95% CI 1.56-1.97) were also significantly associated with higher obesity markers. Associations were more pronounced among women and participants with severe insomnia symptoms. <b>Conclusions:</b> Insomnia severity, sociodemographic disadvantage, and unhealthy behaviors (low physical activity, poor diet, smoking) were all independent correlates of general and visceral adiposity. The findings underscore the need for comprehensive workplace health programs that integrate sleep quality assessment, dietary improvement, and physical activity promotion to prevent obesity and its metabolic consequences.