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 .
Premenopausal overweight women do not lose bone during moderate weight loss with adequate or higher calcium intake.
BACKGROUND Weight loss is associated with bone loss , but this has not been examined in overweight premenopausal women . OBJECTIVE The aim of this study was to assess whether overweight premenopausal women lose bone with moderate weight loss at recommended or higher than recommended calcium intakes . DESIGN Overweight premenopausal women [ n = 44 ; x ( + /-SD ) age : 38 + /- 6.4 y ; body mass index ( BMI ): 27.7 + /- 2.1 kg/m(2 ) ] were r and omly assigned to either a normal ( 1 g/d ) or high ( 1.8 g/d ) calcium intake during 6 mo of energy restriction [ weight loss ( WL ) groups ] or were recruited for weight maintenance at 1 g Ca/d intake .  Regional bone mineral density and content were measured by dual-energy X-ray absorptiometry , and markers of bone turnover were measured before and after weight loss . True fractional calcium absorption ( TFCA ) was measured at baseline and during caloric restriction by using a dual-stable calcium isotope method . RESULTS The WL groups lost 7.2 + /- 3.3 % of initial body weight . No significant decrease in BMD or rise in bone turnover was observed with weight loss at normal or high calcium intake . The group that consumed high calcium showed a strong relation ( r = 0.71 ) between increased femoral neck bone mineral density and increased serum 25-hydroxyvitamin D. No significant effect of weight loss on TFCA was observed , and the total calcium absorbed was adequate at 238 + /- 81 and 310 + /- 91 mg/d for the normal- and high-calcium WL groups , respectively . CONCLUSION Overweight premenopausal women do not lose bone during weight loss at the recommended calcium intake , which may be explained by sufficient amounts of absorbed calcium
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 .