Seasonal effects on vitamin D status influence outcomes of lifestyle intervention in overweight and obese women with polycystic ovary syndrome

Objective: To investigate the effect of undertaking lifestyle interventions during periods of seasonal change on vitamin D status and health outcomes in overweight/obese women with polycystic ovary syndrome (PCOS). Design: Retrospective, unplanned secondary analysis of two cohorts during different seasons. Setting: Outpatient clinical research unit. Patient(s): Fifty overweight/obese women with PCOS. Intervention(s): Twenty-week lifestyle modification program (Clinical Trials registration no.: ACTRN12606000198527); one cohort started in winter and finished in summer, and one started in summer and finished in winter. Main Outcome Measure(s): 25-Hydroxyvitamin D (25OH-D), weight, waist circumference (WC), body composition, cardiovascular disease (CVD) risk factors, and menstrual cycle length. Result(s): Baseline 25OH-D levels were 27.6 +/- 9.0 nmol/L. The winter cohort had lower 25OH-D levels at baseline, which increased over 20 weeks, whereas the summer cohort started with higher levels which decreased. Changes in 25OH-D were inversely correlated with changes in WC and cholesterol when controlling for baseline values, such that increases in 25OH-D were associated with greater reductions in WC and cholesterol. Conclusion(s): Obesity and CVD risk profiles improved in vitamin D-deficient women with PCOS after a 20-week lifestyle intervention during which vitamin D status improved with seasonal change. (c) 2013 by American Society for Reproductive Medicine.