Cross-sectional and prospective cohort study of serum 25-hydroxyvitamin D level and obesity in adults: the HUNT study. Large Doses of Vitamin D Fail to Increase 25-Hydroxyvitamin D Levels or to Alter Cardiovascular Risk Factors in Obese Adolescents: A Pilot Study. A 12-week double-blind randomized clinical trial of vitamin D3 supplementation on body fat mass in healthy overweight and obese women Effects of weight loss on serum vitamin D in postmenopausal women. Rising serum 25-hydroxy-vitamin D levels after weight loss in obese women correlate with improvement in insulin resistance. Associations between 25-hydroxyvitamin D and weight gain in elderly women. Vitamin D receptor Cdx-2-dependent response of central obesity to vitamin D intake in the subjects with type 2 diabetes: a randomised clinical trial. Cross-sectional and longitudinal relation between serum 25-hydroxyvitamin D and body mass index: the Tromsø study Vitamin D3 supplementation during weight loss: a double-blind randomized controlled trial. Vitamin D status modification by two slightly hypocaloric diets in young overweight/obese women. No improvement in cardiovascular risk factors in overweight and obese subjects after supplementation with vitamin D3 for 1 year. Effect of adiposity on vitamin D status and the 25-hydroxycholecalciferol response to supplementation in healthy young and older Irish adults. Preliminary data about the influence of vitamin D status on the loss of body fat in young overweight/obese women following two types of hypocaloric diet. Serum 25-Hydroxyvitamin D and the Incidence of Acute Viral Respiratory Tract Infections in Healthy Adults The Effect of High-Dose Vitamin D Supplementation on Calciotropic Hormones and Bone Mineral Density in Obese Subjects with Low Levels of Circulating 25-Hydroxyvitamin D: Results from a Randomized Controlled Study Response to Vitamin D3 Supplementation in Obese and Non-Obese Caucasian Adolescents Effect of Vitamin D Supplementation on Obesity‐Induced Insulin Resistance: A Double‐Blind, Randomized, Placebo‐Controlled Trial
Experimental studies suggest that vitamin D modulates the activity of adipocytes . The authors examined baseline serum 25-hydroxyvitamin D ( 25(OH)D )  level in relation to prevalent and cumulative incident obesity in Norway . A cohort of 25,616 adults aged 19 - 55 years participated in both the second and third surveys of the Nord-Trøndelag Health Study ( HUNT 2 ( 1995 - 1997 ) and HUNT 3 ( 2006 - 2008 ) ) .  Serum 25(OH)D levels measured at baseline and  anthropometric measurements  taken at both baseline and follow-up were available for a r and om sample of 2,460 subjects . Overall , 40 % of the 2,460 subjects had a serum 25(OH)D level less than 50.0 nmol/L , and 37 % had a level of 50.0 - 74.9 nmol/L. The prevalence and cumulative incidence of obesity , defined as body mass index ( weight (kg)/height (m)(2 ) ) ≥30 , were 12 % and 15 % , respectively . Lower serum 25(OH)D level was associated with a higher prevalence of obesity . In the 2,165 subjects with baseline BMI less than 30 , a serum 25(OH)D level less than 50.0 nmol/L was associated with a significantly increased odds ratio for incident obesity during follow-up ( adjusted odds ratio = 1.73 , 95 % confidence interval : 1.24 , 2.41 ) . When prevalent and incident obesity were classified according to waist circumference ( ≥88 cm for women , ≥102 cm for men ) , similar results were obtained . In addition to prevalent obesity , a serum 25(OH)D level less than 50.0 nmol/L was significantly associated with new-onset obesity in adults PURPOSE Vitamin D deficiency and cardiometabolic risk factors are common in obese adolescents . Observational studies demonstrate an inverse relationship among serum 25-hydroxyvitamin D ( 25OHD ) and obesity , insulin resistance , and inflammatory cytokines . This pilot study explores if vitamin D supplementation could reduce serum concentrations of inflammatory cytokines ( interleukin [ IL ] 6 , IL-10 , tumor necrosis factor α ) , adiponectin , lipids , hemoglobin A1C , and high-sensitivity C-reactive protein ( hs-CRP ) . A secondary aim was to determine the associations between baseline serum 25OHD concentrations and body mass index ( BMI ) , hs-CRP , inflammatory cytokines , and lipids . METHODS Overweight and obese adolescents enrolled in this 24-week , r and omized , double-blind study were given 150,000 IU ergocalciferol or placebo at baseline and 12 weeks . Outcome measurements included serum 25OHD , inflammatory cytokines , adiponectin , hs-CRP , lipids , hemoglobin A1C , and BMI at baseline , 12 , and 24 weeks . RESULTS Of 40 participants , 31 ( 78 % ) completed the study . Mean ± st and ard error 25OHD levels were similar in vitamin D and placebo groups at baseline ( 19.6 ± 5.3 vs. 25.8 ± 10.8 ng/mL ) and 24 weeks ( 20.1 ± 3.4 vs. 24.6 ± 8.4 ng/mL ) . Inflammatory and cardiovascular markers were not significantly different between groups at 24 weeks . Serum 25OHD at baseline was associated with BMI ( r = -.44 [ 95 % confidence interval , -.66 to -.15 ] ) but not with other outcome measures . CONCLUSIONS Supplementation with vitamin D at 150,000 IU every 3 months failed to increase serum 25OHD or alter inflammatory markers and lipids in overweight and obese youth . Further studies are needed to establish the dose of vitamin D required to increase 25OHD and determine potential effects on metabolic risk factors in obese teens Background Vitamin D concentrations are linked to body composition indices , particularly body fat mass . Relationships between hypovitaminosis D and obesity , described by both BMI and waist circumference , have been mentioned . We have investigated the effect of a 12-week vitamin D3 supplementation on anthropometric indices in healthy overweight and obese women . Methods In a double-blind , r and omized , placebo-controlled , parallel-group trial , seventy-seven participants ( age 38±8.1 years , BMI 29.8±4.1 kg/m2 ) were r and omly allocated into two groups : vitamin D ( 25 μg per day as cholecalciferol ) and placebo ( 25 μg per day as lactose ) for 12 weeks . Body weight , height , waist , hip , fat mass , 25(OH ) D , iPTH , and dietary intakes were measured before and after the intervention . Results Serum 25(OH)D significantly increased in the vitamin D group compared to the placebo group ( 38.2±32.7 nmol/L vs. 4.6±14.8 nmol/L ; P<0.001 ) and serum iPTH concentrations were decreased by vitamin D3 supplementation ( -0.26±0.57 pmol/L vs. 0.27±0.56 pmol/L ; P<0.001 ) . Supplementation with vitamin D3 caused a statistically significant decrease in body fat mass in the vitamin D group compared to the placebo group ( -2.7±2.1 kg vs. -0.47±2.1 kg ; P<0.001 ) . However , body weight and waist circumference did not change significantly in both groups . A significant reverse correlation between changes in serum 25(OH ) D concentrations and body fat mass was observed ( r = -0.319 , P = 0.005 ) . Conclusion Among healthy overweight and obese women , increasing 25(OH ) D concentrations by vitamin D3 supplementation led to body fat mass reduction . This trial is registered at clinical trials.gov as NCT01344161 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 OBJECTIVE The objective of the study was to examine changes of 25-hydroxy-vitamin D ( 25OHD ) and PTH blood levels 4 and 20 wk after low-calorie diet-induced weight loss . METHODS Forty-four obese women [ aged 40.6 + /- 11.4 yr , body mass index ( BMI ) 36.7 + /- 4.9 kg/m(2 ) ] and 25 controls ( BMI 22.9 + /- 1.5 kg/m(2 ) ) were examined .  Anthropometric and cardiometabolic parameters and 25OHD and PTH levels  were determined at baseline and 4 and 20 wk after a low-calorie diet . RESULTS At baseline , 25OHD levels were lower in obese compared with control subjects ( 17 + /- 6.0 vs. 23.8 + /- 8.7 ng/ml , P < 0.001 ) , whereas no differences were found in PTH levels . In all women , a negative correlation was found between 25OHD levels and body weight ( BW ) ( r -0.32 , P < 0.001 ) , BMI ( r -0.37 , P < 0.001 ) , waist circumference ( r -0.26 , P < 0.05 ) , and percent fat mass ( r -0.38 , P = 0.001 ) as determined by bioelectrical impedance analysis . The 4-wk low-calorie diet ( n = 37 ) reduced BW and led to significant improvements in the homeostasis model assessment ( HOMA ) index and lipid levels . The 20-wk low-calorie diet ( n = 26 ) result ed in reduction of BW and BMI by 10 % , HOMA index ( 4.7 + /- 3.8 vs. 3.10 + /- 1.7 , P < 0.01 ) , and lipids levels ( except high density lipoprotein cholesterol ) and increase in 25OHD ( 15.4 + /- 6.0 vs. 18.3 + /- 5.1 ng/ml , P < 0.05 ) , compared with baseline . PTH levels were unchanged . The increase of 25OHD levels was associated with the reduction of insulin levels and HOMA index ( r -0.43 , P < 0.05 ) . CONCLUSIONS Blood 25OHD levels were low in obese women and correlated inversely with severity measures of obesity . Weight loss of 10 % after low-calorie diet increased 25OHD levels , and this increase was mainly associated with improvement of insulin resistance BACKGROUND 25-Hydroxyvitamin D [ 25(OH)D ] levels are lower in obese individuals . Determining whether low vitamin D status can predispose weight gain requires a longitudinal study . METHODS From a community-based multicenter U.S. prospect i ve cohort of 9704 ( Study of Osteoporotic Fractures [ SOF ] ) , 4659 women aged ≥65 with baseline 25(OH)D measurement were followed for 4.5 years . They were weighed at baseline and follow-up visits , and a subset ( n=1054 ) had 25(OH)D levels remeasured at follow-up . RESULTS Women with 25(OH)D levels ≥30 ng/mL had lower baseline weight ( 141.6 pounds ) compared to women with 25(OH)D levels < 30 ng/mL ( 148.6 pounds ) ( p<0.001 ) . Overall , 25(OH)D status was not associated with weight change over 4.5 years , although there was a significant interaction between 25(OH)D status and weight change category ( loss , gain , stable ) ( p<0.0001 ) . In women who gained ≥5 % weight , those with baseline 25(OH)D levels ≥30 ng/mL gained 16.4 pounds ( 12.2 % of baseline weight ) over 4.5 years compared to 18.5 pounds ( 13.9 % of baseline weight ) in women with levels < 30 ng/mL ( p=0.04 ) . In women who lost ≥5 % weight or remained stable ( < 5 % weight change ) , there was no association between 25(OH)D status at baseline and weight change . Among women who gained weight and had 25(OH)D measured at both visits , having sustained or developing 25(OH)D levels ≥30 ng/mL was associated with less weight gain between visits ( 14.81 vs. 16.34 pounds , p=0.04 ) . CONCLUSIONS Higher 25(OH)D levels are associated with lower weight gains , suggesting low vitamin D status may predispose to fat accumulation This study aim ed to investigate the effects of daily intake of vitamin D-fortified yogurt drink ( doogh ) on central obesity indicators in subjects with type 2 diabetes ( T2D ) and the possible modulation of this effect by vitamin D receptor ( VDR ) Cdx-2 genotypes . A total of sixty T2D subjects were r and omly allocated to two groups to receive either plain doogh ( PD ; n 29 , containing 170 mg Ca and no vitamin D/250 ml ) or vitamin D3-fortified doogh ( FD ; n 31 , containing 170 mg Ca and 12·5 μg/250 ml ) twice a day for 12 weeks . 25-hydroxyvitamin D ( 25(OH)D ) , glycaemic as well as adiposity indicators were evaluated before and after the intervention . VDR-Cdx-2 genotypes in extended number of T2D subjects in the FD group ( n 60 ) were determined as AA , GA and GG . After 12 weeks , in FD compared with PD , serum 25(OH)D increased ( + 35·4 v. -4·8 nmol/l ; P<0·001 ) and mean changes of waist circumference ( WC ; -1·3 v. + 1·6 cm ; P=0·02 ) , body fat mass ( FM ; -1·9 v. + 0·60 % ; P=0·008 ) , truncal fat ( TF ; -1·1 v. 0·13 % ; P=0·003 ) and visceral adipose tissue ( -0·80 v. + 0·37 AU ; P<0·001 ) decreased significantly . Circulating 25(OH)D was raised only in the AA group ( 34·8 nmo/l in AA group v. -6·4 nmol/l in AG and -1·6 nmol/l in GG groups ; P<0·001 ) , which was accompanied by a significant decrease in changes of WC ( P=0·004 ) , FM% ( P=0·01 ) and TF% ( P<0·001 ) in the AA genotype . Daily intake of vitamin D-FD for 12 weeks improved the central obesity indices in T2D subjects , and the improvement was more pronounced in the carriers of the AA genotype of VDR-Cdx-2 Purpose The serum 25-hydroxyvitamin D ( 25(OH)D ) levels are lower in obese than lean subjects . The present study examines the cross-sectional and longitudinal relations between body mass index ( BMI ) and serum 25(OH)D , and the serum 25(OH)D response to vitamin D supplementation  in relation to BMI . Methods The Tromsø study is a longitudinal population -based multi purpose study . The fourth survey was conducted in 1994 and the sixth in 2008 . The intervention study was a 1-year placebo-controlled r and omized intervention trial , where the results from the 93 subjects given 40,000 IU per week are presented . Results A total of 10,229 subjects were included in the 2008 cross-sectional study . There was a significant negative association between serum 25(OH)D levels and BMI which was also present during the winter months . Serum 25(OH)D levels varied through seasons , but not BMI . In the longitudinal study from 1994 to 2008 which included 2,656 subjects , change in BMI was a significant negative predictor of change in 25(OH)D. In the intervention study , there was a significant and negative correlation between BMI and serum 25(OH)D both at baseline and at the end of the study . The increase in serum 25(OH)D after 1 year was significantly and inversely related to baseline BMI . Conclusions We have confirmed the strong association between serum 25(OH)D and BMI . The very obese need higher vitamin D doses than lean subjects to achieve the same serum 25(OH)D levels BACKGROUND Vitamin D deficiency is associated with obesity ; whether repletion supports weight loss and changes obesity-related biomarkers is unknown . OBJECTIVE We compared 12 mo of vitamin D3 supplementation with placebo  on weight , body composition , insulin , and C-reactive protein ( CRP ) in postmenopausal women in a weight-loss intervention . DESIGN A total of 218 overweight/obese women ( 50 - 75 y of age ) with serum 25-hydroxyvitamin D [ 25(OH)D ] ≥10 ng/mL but < 32 ng/mL were r and omly assigned to weight loss + 2000 IU oral vitamin D3/d or weight loss + daily placebo . The weight-loss intervention included a reduced-calorie diet ( 10 % weight loss goal ) and 225 min/wk of moderate-to-vigorous aerobic activity . Mean 12-mo changes in weight , body composition , serum insulin , CRP , and 25(OH)D were compared between groups ( intent-to-treat ) by using generalized estimating equations . RESULTS A total of 86 % of participants completed the 12-mo measurements . The mean ( 95 % CI ) change in 25(OH)D was 13.6 ( 11.6 , 15.4 ) ng/mL in the vitamin D3 arm compared with -1.3 ( -2.6 , -0.3 ) ng/mL in the placebo arm ( P < 0.0001 ) . Changes in weight [ -7.1 ( -8.7 , -5.7 ) compared with -7.4 ( -8.1 , -5.4 ) kg ] , body mass index ( in kg/m(2 ) : both -2.8 ) , waist circumference [ -4.9 ( -6.7 , -2.9 ) compared with -4.5 ( -5.6 , -2.6 ) cm ] , percentage body fat [ -4.1 ( -4.9 , -2.9 ) compared with -3.5 ( -4.5 , -2.5 ) ] , trunk fat [ -4.1 ( -4.7 , -3.0 ) compared with -3.7 ( -4.3 , -2.9 ) kg ] , insulin [ -2.5 ( -3.4 , -1.7 ) compared with -2.4 ( -3.3 , -1.4 ) μU/mL ] , and CRP [ -0.9 ( -1.2 , -0.6 ) compared with -0.79 ( -0.9 , -0.4 ) mg/L ] [ corrected ] were similar between groups ( all P > 0.05 ) . Compared with women who achieved 25(OH)D < 32 ng/mL , women r and omly assigned to vitamin D who became replete ( ie , 25(OH)D ≥32 ng/mL ) lost more weight [ -8.8 ( -11.1 , -6.9 ) compared with -5.6 ( -7.2 , -5.0 ) kg ; P = 0.05 ] , waist circumference [ -6.6 ( -9.3 , -4.3 ) compared with -2.5 ( -4.6 , -2.0 ) cm ; P = 0.02 ] , and percentage body fat [ -4.7 ( -6.1 , -3.5 ) compared with -2.6 ( -3.9 , -2.2 ) ; P = 0.04 ] . Among women with complete pill counts ( 97 % adherence ) , the mean decrease in CRP was 1.18 mg/mL ( 46 % ) in the vitamin D arm compared with 0.46 mg/mL ( 25 % ) in the placebo arm ( P = 0.03 ) . CONCLUSIONS Vitamin D3 supplementation  during weight loss did not increase weight loss or associated factors compared with placebo ; however , women who became replete experienced greater improvements . This trial was registered at clinical trials.gov as NCT01240213 Obesity has been linked with poorer vitamin D status . The aim of this work was to analyze the changes in vitamin D status and body weight of 61 young , overweight/obese women following two different weight control programs . The study subjects were r and omly assigned to one of two slightly hypocaloric diets : diet V , in which the consumption of greens and vegetables was increased , or diet C , in which the consumption of cereals ( some of which were enriched with vitamin D ) was increased .  Dietary , anthropometric , and biochemical data were collected at the start of the study and at 2 weeks . At the beginning of the study , when taking into account only those women with a vitamin D intake below that recommended , obese women had a significantly lower mean serum 25(OH)D concentration than those who were lighter . Dietary intervention led to a greater reduction in energy intake among group C subjects ; their weight was also that which was most reduced . In addition , the vitamin D intake and serum 25(OH)D values were increased only in group C women . Excess body weight was associated with deterioration in vitamin D status , especially when the intake of this vitamin was lower than that recommended . Subjects with higher serum vitamin D at the beginning of the study lost more weight than those subjects with lower initial values . Diet C was associated with a greater weight loss than diet V , and led to a greater increase in vitamin D intake and serum 25(OH)D levels . This might be of interest in the improvement of health in people trying to lose weight BACKGROUND AND AIM Cross-sectional studies indicate vitamin D to be of importance for glucose tolerance , blood pressure and serum lipids , but whether supplementation with vitamin D would improve cardio-vascular risk factors is not known . DESIGN AND SETTING The study was a 1 year , double blind placebo-controlled intervention trial performed at the University Hospital of North Norway from November 2005 to October 2007 . Subjects . A total of 438 overweight or obese subjects , 21 - 70 years old , were included and 330 completed the study . INTERVENTIONS The subjects were r and omized to vitamin D ( cholecalciferol , vitamin D(3 ) ) 40 000 IU per week ( DD group ) , vitamin D 20 000 IU per week ( DP group ) , or placebo ( PP group ) . All subjects were given 500 mg calcium daily . MAIN OUTCOME MEASURES Fasting serum lipids and blood pressure were measured and an oral glucose tolerance test performed at start and end of the study . RESULTS At baseline the mean serum 25(OH)D levels were 58 nmol L(-1 ) ( all subjects ) and increased to 140 and 101 nmol L(-1 ) in the DD and DP groups , respectively . No significant differences were found between the three groups regarding change in measures of glucose metabolism or serum lipids . In the DP group , there was a slight but significant increase in systolic blood pressure compared with the placebo group . CONCLUSIONS Our results do not support a positive effect of vitamin D on glucose tolerance , blood pressure or serum lipids . Further studies in subjects with low serum 25(OH)D levels combined with impaired glucose tolerance , hypertension or dyslipidaemia are needed There is increasing epidemiological evidence linking sub-optimal vitamin D status with overweight and obesity . Although increasing BMI and adiposity have also been negatively associated with the change in vitamin D status following supplementation , results have been equivocal . The aim of this r and omised , placebo-controlled study was to investigate the associations between anthropometric measures of adiposity and the wintertime serum 25-hydroxycholecalciferol ( 25(OH)D ) response to 15 μg cholecalciferol per d in healthy young and older Irish adults . A total of 110 young adults ( 20 - 40 years ) and 102 older adults ( ≥ 64 years ) completed the 22-week intervention with > 85 % compliance . The change in 25(OH)D from baseline was calculated . Anthropometric measures of adiposity taken at baseline included height , weight and waist circumference ( WC ) , along with skinfold thickness measurements to estimate fat mass ( FM ) . FM was subsequently expressed as FM ( kg ) , FM ( % ) , FM index ( FMI ( FM kg/height m2 ) ) and as a percentage ratio to fat-free mass ( FFM ) . In older adults , vitamin D status was inversely associated with BMI ( kg/m2 ) , WC ( cm ) , FM ( kg and % ) , FMI ( kg/m2 ) and FM : FFM ( % ) at baseline ( r - 0·33 , - 0·36 , - 0·33 , - 0·30 , - 0·33 and - 0·27 , respectively , all P values < 0·01 ) . BMI in older adults was also negatively associated with the change in 25(OH)D  following supplementation ( β - 1·27 , CI - 2·37 , - 0·16 , P = 0·026 ) ; however , no such associations were apparent in younger adults . Results suggest that adiposity may need to be taken into account when determining an adequate wintertime dietary vitamin D intake for healthy older adults residing at higher latitudes The loss of weight was analysed in a group of sixty overweight/obese women of childbearing age ( 20 - 35 years ) according to their initial vitamin D status . Subjects were r and omly assigned to one of two slightly hypocaloric diets : Diet V , in which the consumption of vegetables was increased , or Diet C , in which the relative consumption of cereals ( especially breakfast cereals ) was increased .  Dietetic , anthropometric and biochemical data were collected at the start of the study and again at 2 weeks after dividing the women into groups depending on their having an initial serum 25-hydroxyvitamin D ( 25(OH)D ) concentration of < 50 nmol/l ( LD ) or > or=50 nmol/l ( HD ) . Dietary intervention led to a reduction in energy intake , body weight and BMI in all groups . The HD women showed greater body fat losses during the study than the LD women ( 1.7 ( SD 1.8 ) kg compared to 0.5 ( SD 0.8 ) kg ) . A better vitamin D status therefore aided the loss of body fat over the experimental period ( OR 0.462 ; CI 0.271 , 0.785 ; P < 0.001 ) . However , when the dietary groups were analysed separately , this effect was only seen in the C subjects ( OR 0.300 ; CI 0.121 , 0.748 ; P < 0.001 ) . The present results suggest that women with a better vitamin D status respond more positively to  hypocaloric diets  and lose more body fat ; this was especially clear among the C subjects who had a greater vitamin D supply during the experimental period Background Declining serum concentrations of 25-hydroxyvitamin D seen in the fall and winter as distance increases from the equator may be a factor in the seasonal increased prevalence of influenza and other viral infections . This study was done to determine if serum 25-hydroxyvitamin D concentrations correlated with the incidence of acute viral respiratory tract infections . Methodology / Findings In this prospect i ve cohort study serial monthly concentrations of 25-hydroxyvitamin D were measured over the fall and winter 2009–2010 in 198 healthy adults , blinded to the nature of the substance being measured . The participants were evaluated for the development of any acute respiratory tract infections by investigators blinded to the 25-hydroxyvitamin D concentrations . The incidence of infection in participants with different concentrations of vitamin D was determined . One hundred ninety-five ( 98.5 % ) of the enrolled participants completed the study . Light skin pigmentation , lean body mass , and supplementation with vitamin D were found to correlate with higher concentrations of 25-hydroxyvitamin D. Concentrations of 38 ng/ml or more were associated with a significant ( p<0.0001 ) two-fold reduction in the risk of developing acute respiratory tract infections and with a marked reduction in the percentages of days ill . Conclusions / Significance Maintenance of a 25-hydroxyvitamin D serum concentration of 38 ng/ml or higher should significantly reduce the incidence of acute viral respiratory tract infections and the burden of illness caused thereby , at least during the fall and winter in temperate zones . The findings of the present study provide direction for and call for future interventional studies examining the efficacy of vitamin D supplementation in reducing the incidence and severity of specific viral infections , including influenza , in the general population and in sub population s with lower 25-hydroxyvitamin D concentrations , such as pregnant women , dark skinned individuals , and the obese Low levels of 25-hydroxyvitamin D ( 25OHD ) are associated with increased bone turnover and risk of fractures . Plasma 25OHD is inversely related to body mass index , and vitamin D deficiency is common in obesity . We aim ed to determine whether vitamin D supplementation affects bone turnover and bone mineral density ( BMD ) in obese subjects . Fifty-two healthy obese men and women aged 18–50 years with plasma 25OHD levels below 50 nmol/L were r and omized to 7,000 IU of cholecalciferol daily or placebo for 26 weeks . We measured plasma levels of 25OHD , parathyroid hormone ( PTH ) , and markers of bone turnover , as well as BMD at the hip , spine , forearm , and whole body . Compared with placebo , treatment with cholecalciferol  increased mean plasma 25OHD from 35 to 110 nmol/L ( p < 0.00001 ) and significantly decreased PTH ( p < 0.05 ) . BMD increased significantly at the forearm by 1.6 ± 0.7 % ( p = 0.03 ) . The bone resorption marker C-terminal telopetide of type 1 collagen ( CTX ) decreased borderline significantly in the cholecalciferol group compared with the placebo group ( p = 0.07 ) . Changes in plasma 25OHD correlated inversely with changes in plasma levels of bone-specific alkaline phosphatase ( r = −0.38 , p = 0.01 ) and CTX ( r = −0.33 , p = 0.03 ) . Changes in CTX correlated inversely with changes in spine BMD ( r = −0.45 , p = 0.04 ) . Increasing circulating 25OHD levels by cholecalciferol treatment is of importance to bone health in young obese subjects as increased levels of 25OHD are associated with a decrease in both PTH and bone turnover and with an increase in BMD at the forearm Background / Aims : Vitamin D deficiency is highly prevalent in obese children , and obese children tend to respond poorly to vitamin D supplementation . The objective of the study was to compare the response to vitamin D3 supplementation ( 2,000 IU once daily for 12 weeks ) between obese and non-obese Caucasian adolescents . Methods : The study design was open label non-r and omized . It was carried out at a single center . Eighteen obese adolescents ( aged 12–18 years ) and the same number of age- , gender- and season-matched non-obese adolescents received vitamin D3 ( 2,000 IU/day ) orally for 12 weeks . Total serum 25-hydroxyvitamin D [ 25(OH)D ] , parathyroid hormone , calcium and phosphorus were measured at baseline and at the end of the 12-week period . Results : The mean baseline 25(OH)D level was higher in the non-obese compared to the obese subjects ( mean 28.9 vs. 25.2 ng/ml ; p = 0.029 ) . The increment in 25(OH)D levels following  vitamin D supplementation was significantly lower in the obese adolescents ( mean change 5.8 vs. 9.8 ng/ml ; p = 0.019 ) . Conclusions : Higher doses of vitamin D are required to treat vitamin D deficiency in obese adolescents compared to their non-obese peers Objective The aim was to investigate whether vitamin D supplementation , combined with a hypocaloric diet , could have an independent effect on insulin sensitivity in subjects with both overweight and hypovitaminosis D. Changes from baseline in anthropometric parameters , body composition , glucose tolerance , and insulin secretion were considered as secondary outcomes . Methods Eighteen volunteers who were nondiabetic and vitamin D deficient and had BMI > 25 kg/m2 were r and omized ( 1:1 ) in a double‐blind manner to a hypocaloric diet + either oral cholecalciferol at 25,000 IU/wk or placebo for 3 months . Hyperinsulinemic‐euglycemic clamp to measure insulin sensitivity  was performed at baseline and after intervention . Results Body weight in both groups decreased significantly ( −7.5 % in the vitamin D group and −10 % in the placebo group ; P < 0.05 for both ) , with no between‐group differences . Serum 25‐hydroxyvitamin D levels in the vitamin D group increased considerably ( from 36.7 ± 13.2 nmol/L to 74.8 ± 18.7 nmol/L ; P < 0.001 ) . Insulin sensitivity in the vitamin D group improved ( from 4.6 ± 2.0 to 6.9 ± 3.3 mg·kg−1·min−1 ; P < 0.001 ) , whereas no changes were observed in the placebo group ( from 4.9 ± 1.1 to 5.1 ± 0.3 mg·kg−1·min−1 ; P = 0.84 ) . Conclusions Cholecalciferol supplementation , combined with a weight loss program , significantly improves insulin sensitivity in healthy subjects with obesity and might represent a personalized approach for insulin‐resistant subjects with obesity
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 .