Vitamin D status and weight loss: a systematic review and meta-analysis of randomized and nonrandomized controlled weight-loss trials.
Obesity is associated with lower concentrations of serum 25-hydroxyvitamin D; however, uncertainty exists as to the direction of causation. To date, meta-analyses of randomized controlled vitamin D-supplementation trials have shown no effect of raising circulating vitamin D on body weight, although several weight-loss-intervention trials have reported an increase in circulating vitamin D after weight reduction.



We undertook a systematic review and meta-analysis of randomized and nonrandomized controlled trials to determine whether weight loss compared with weight maintenance leads to an increase in serum 25-hydroxyvitamin D.



A systematic search for controlled weight-loss-intervention studies published up to 31 March 2016 was performed. Studies that included participants of any age with changes in adiposity and serum 25-hydroxyvitamin D as primary or secondary outcomes were considered eligible.



We identified 4 randomized controlled trials (n = 2554) and 11 nonrandomized controlled trials (n = 917) for inclusion in the meta-analysis. Random assignment to weight loss compared with weight maintenance resulted in a greater increase in serum 25-hydroxyvitamin D with a mean difference of 3.11 nmol/L (95% CI: 1.38, 4.84 nmol/L) between groups, whereas a mean difference of 4.85 nmol/L (95% CI: 2.59, 7.12 nmol/L) was observed in nonrandomized trials. No evidence for a dose-response effect of weight loss on the change in serum 25-hydroxyvitamin D was shown overall.



Our results indicate that vitamin D status may be marginally improved with weight loss in comparison with weight maintenance under similar conditions of supplemental vitamin D intake. Although additional studies in unsupplemented individuals are needed to confirm these findings, our results support the view that the association between obesity and lower serum 25-hydroxyvitamin D may be due to reversed causation with increased adiposity leading to suboptimal concentrations of circulating vitamin D. This trial was registered at www.crd.york.ac.uk/PROSPERO/ as CRD42015023836.
Department of Human Nutrition, University of Otago, Dunedin, New Zealand simonette.mallard@otago.ac.nz.
Simonette R
SR
Mallard
Department of Human Nutrition, University of Otago, Dunedin, New Zealand.
Anna S
AS
Howe
Department of Human Nutrition, University of Otago, Dunedin, New Zealand.
Lisa A
LA
Houghton
D050154:Adiposity; D000328:Adult; D000368:Aged; D000068959:Body Weight Maintenance / Q000502:physiology*; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000150:complications*; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000097:blood* / Q000627:therapeutic use; D014808:Vitamin D Deficiency / Q000097:blood / Q000209:etiology* / Q000517:prevention & control; D014815:Vitamins / Q000008:administration & dosage / Q000097:blood* / Q000627:therapeutic use; D015431:Weight Loss / Q000502:physiology*
D014815:Vitamins; D014807:Vitamin D; C104450:25-hydroxyvitamin D
meta-analysis; obesity; serum 25-hydroxyvitamin D; vitamin D; weight loss