Collectively , these outcomes support a volumetric dilution of vitamin D. The slopes of the respective regression lines , however , indicate a smaller increase in 25OHD than would be expected from a direct mobilization of stores into the circulation .
Hence , sequestration of 25OHD and its conversion to inactive metabolites would also play a role .
The purpose of this review was to confirm a volumetric dilution of vitamin D in obesity .
It was based on the hypothesis that weight loss , particularly fat loss , would increase serum 25-hydroxyvitamin D ( 25OHD ) in the obese .
Effects of weight loss on serum vitamin D in postmenopausal women.
BACKGROUND Low concentrations of circulating vitamin D are common with obesity and may represent a potential mechanism explaining the elevated risk of certain cancers and cardiovascular outcomes observed in individuals who are overweight or obese . OBJECTIVE The objective of this study was to investigate the effects of 12 mo of weight loss through caloric restriction , exercise intervention , or both on serum 25-hydroxyvitamin D [ 25(OH)D ] concentrations . DESIGN Overweight and obese postmenopausal women ( n = 439 ) were r and omly assigned to 1 of 4 groups : 1 ) diet modification ( n = 118 ) , 2 ) exercise ( n = 117 ) , 3 ) diet + exercise ( n = 117 ) , or 4 ) control ( n = 87 ) . The diet intervention was a group-based reduced-calorie program with a 10 % weight-loss goal . The exercise intervention consisted of 45 min of moderate-to-vigorous intensity aerobic activity daily for 5 d/wk . Serum 25(OH)D concentrations were measured by using a competitive chemiluminescent immunoassay at baseline and 12 mo . RESULTS No significant change in serum 25(OH)D was found between the intervention and control groups . Women who lost < 5 % , 5 - 9.9 % , 10 - 14.9 % , or ≥15 % of baseline weight had mean increases in 25(OH)D of 2.1 , 2.7 , 3.3 , and 7.7 ng/mL , respectively ( P for trend = 0.002 ) . Baseline vitamin D status did not modify the effect of the interventions on weight loss or body-composition changes at the 12-mo follow-up . CONCLUSION A greater degree of weight loss , achieved through either a reduced-calorie diet or increased exercise , is associated with increased circulating 25(OH)D concentrations . This trial is registered at clinical trials.gov as NCT00470119
Collectively , these outcomes support a volumetric dilution of vitamin D. The slopes of the respective regression lines , however , indicate a smaller increase in 25OHD than would be expected from a direct mobilization of stores into the circulation .
Hence , sequestration of 25OHD and its conversion to inactive metabolites would also play a role .
The purpose of this review was to confirm a volumetric dilution of vitamin D in obesity .
It was based on the hypothesis that weight loss , particularly fat loss , would increase serum 25-hydroxyvitamin D ( 25OHD ) in the obese .