The Associations of Vitamin D Status and Lifestyle Behaviors with General Obesity and Metabolically Unhealthy Obesity in Chinese Children and Adolescents.

Background: Vitamin D and lifestyle behaviors are closely related to children's health. However, current research on the combined influences of vitamin D and adherence to 24-Hour Movement Guidelines (24-HMG) on childhood obesity remains scarce. Our study aimed to examine individual and joint associations of vitamin D status and the number of recommendations for adhering to 24-HMG with obesity among Chinese children and adolescents.

Methods: In this cross-sectional study, a total of 4625 participants from Shenzhen, China, were recruited. Vitamin D status was classified into two categories: adequacy and inadequacy. The 24-HMG was obtained from a validated questionnaire, including moderate-to-vigorous physical activity, screen time, and sleep duration. General obesity and metabolically unhealthy obesity (MUO) were the outcomes of this study. The logistic regression model was performed to examine the associations between vitamin D status, the number of guidelines met, and obesity.

Results: Vitamin D inadequacy was associated with increased odds of general obesity and MUO, with adjusted odds ratios (95% CIs) of 1.551 (1.080-2.226) and 2.205 (1.319-3.686). Meeting 2-3 recommendations of 24-HMG was associated with decreased odds of general obesity, with adjusted odds ratios (95% CIs) of 0.777 (0.626-0.965). Compared with the vitamin D adequacy/meeting 2-3 guidelines group, the vitamin D inadequacy/meeting 0-1 guideline group was positively related to general obesity (adjusted odd ratio, 1.826 [95% CI: 1.167-2.857]) and MUO (2.160, 1.175-3.972). In addition, the population-attributable fractions of vitamin D inadequacy or/and meeting 0-1 guideline were 28.4% (95% CI: 2.5-54.4%) for general obesity and 42.3% (95% CI: 11.5-73.1%) for MUO.

Conclusions: Our findings displayed that the combined associations of vitamin D inadequacy and meeting 0-1 recommendations of 24-HMG were linked to high odds of general obesity and MUO, respectively. Understanding these relationships could provide a theoretical basis for effective preventive strategies and interventions for childhood obesity.