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 .
Influence of moderate energy restriction and seafood consumption on bone turnover in overweight young adults.
BACKGROUND Overweight and obesity are increasing in young adults . However , moderate energy restriction aim ed at lowering body weight may promote bone turnover and bone loss . Inclusion of fish or fish oils in a weight-loss diet may attenuate these adverse skeletal effects . OBJECTIVE We examined the effects of incorporating fish or fish oil into an energy-restricted diet on bone turnover markers in young overweight adults . DESIGN While following a strict hypoenergetic ( -30 % relative to estimated requirements ) diet for 8 wk , 276 overweight men and women [ body mass index ( in kg/m(2 ) ) : 27.5 - 32.5 ; age : 20 - 40 y ) were r and omly assigned to 1 of 4 dietary groups : sunflower-oil capsules ( 3 g/d ; control ) , cod ( 3 x 150 g/wk ) , salmon ( 3 x 150 g/wk ) , and fish-oil capsules ( 3 g/d ) . Body weight , bone biomarkers , and 25-hydroxyvitamin D were measured at baseline and endpoint . Data were analyzed with repeated- measures analysis of variance and general linear models . RESULTS The mean ( + /-SD ) weight loss was 5.14 + /- 3.0 kg ( 5.8 % + /- 3.2 % body weight ) during the 8 wk in the 4 dietary groups combined . Urinary N-telopeptides of type I collagen and serum C-terminal telopeptide of type I collagen increased ( P < 0.05 ) , whereas serum osteocalcin ( but not bone-specific alkaline phosphatase ) decreased ( P < 0.05 ) from baseline to endpoint . Increased fish or fish-oil consumption had no effect ( P > 0.1 ) on the changes in bone markers induced by weight loss . In contrast , increased salmon consumption increased serum 25-hydroxyvitamin D ( P < 0.01 ) . CONCLUSIONS A nutritionally adequate but energy-restricted diet , with different contents of n-3 fatty acids , which result ed in modest weight loss , unfavorably altered bone turnover markers  in young overweight adults . Such changes were not prevented by increased fish or fish-oil consumption
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 .