Cardiorespiratory fitness, adiposity, and serum 25-dihydroxyvitamin D levels in women: the Cooper Center Longitudinal Study.

PURPOSE: We examined the cross-sectional associations among cardiorespiratory fitness (CRF), different measures of adiposity, and serum vitamin D levels in women.
METHODS: Between 2007 and 2010, 1320 women completed a health examination. Measures included body mass index (BMI), waist circumference (WC), waist/hip ratio, percent body fat, CRF based on a maximal treadmill exercise test, and measurement of serum vitamin D. Participants were classified by CRF as unfit (lowest 20%) and fit (remaining 80%) based on age, as well as by clinical cutoff points for adiposity measures, and by categories of serum vitamin D. We examined trends of CRF and adiposity exposures across serum vitamin D categories. We calculated odds ratios (OR) of serum vitamin D insufficiency or deficiency across levels of adiposity exposures before and after adjustment for CRF.
RESULTS: We observed a significant positive trend for CRF across incremental serum vitamin D categories (p<0.001). When compared to ORs for normal weight women, ORs for serum vitamin D insufficiency or deficiency were significantly higher for overweight women within each adiposity exposure (p<0.05). When grouped into categories of fit and unfit (upper 80% and lower 20% of CRF distribution, respectively), serum vitamin D was significantly lower in unfit than in fit women within each stratum of WC and waist/hip ratio and within the normal weight BMI stratum.
CONCLUSIONS: Serum vitamin D levels are positively associated with CRF and negatively associated with different measures of adiposity in women. Higher CRF attenuates the relationship between adiposity level and serum vitamin D. Future prospective studies are warranted.