Sex differences in the association of physical activity levels and vitamin D with obesity, sarcopenia, and sarcopenic obesity: a cross-sectional study

BACKGROUND: The relationship between vitamin D and sarcopenia was inconsistent between men and women. Physical activity (PA) may interact with vitamin D on sarcopenia. However, the sex-specific relationships of vitamin D, PA and sarcopenia have yet elucidated. We aimed to examine the sex differences in the relation between vitamin D status, PA levels, obesity and sarcopenia in community-dwelling middle-aged and older adults, as well as whether vitamin D status is a modifier in the relationship between PA and sarcopenia. METHODS: The current study was a cross-sectional study based on the baseline survey of the West China Health and Aging Trend (WCHAT) study. A total of 3713 participants aged ≥ 50y were included in our study. Sarcopenia was defined according to the Asian Working Group for Sarcopenia (AWGS) 2019 consensus. Obesity was defined by body mass index (BMI) (≥ 28 kg/m2) and body fat mass percentage (≥ 60th percentile in each sex group). 25-hydroxyvitamin D was measured by chemiluminescent microparticle immunoassay and PA was evaluated by a validated China Leisure Time Physical Activity Questionnaire (CLTPAQ). Multinomial logistic regression was performed to examine the relationship between PA, vitamin D and sarcopenia and obesity. RESULTS: Low PA was significantly associated with higher odds of sarcopenia in women only (OR = 1.70,95%CI:1.18,2.46, p < 0.01). Vitamin D deficiency was only associated with sarcopenia in men (OR = 1.85,95%CI: 1.27,2.69, p < 0.01). Low PA was significantly associated with obesity, sarcopenia, and sarcopenic obesity only in participants with serum 25(OH)D < 20 ng/ml. CONCLUSIONS: The role of vitamin D and PA in obesity and sarcopenia was different between men and women, and the relationship between PA and sarcopenia was modified by serum vitamin D status. These findings highlighted the need to supplement vitamin D in individuals with physical inactivity and provide different interventions strategies to sarcopenia in men and women. TRIAL REGISTRATION: Clinical trial number: ChiCTR1800018895. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12877-022-03577-4.