Vitamin D Status and Weight Loss: A Systematic Review and Meta-Analysis of Randomized and Nonrandomized Controlled Weight-Loss Trials

Am J Clin Nutr. 2016 Oct;104(4):1151-1159. doi: 10.3945/ajcn.116.136879. Epub 2016 Sep 7.

Abstract

Background: 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.

Objective: 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.

Design: 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.

Results: 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.

Conclusions: 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.

Keywords: meta-analysis; obesity; serum 25-hydroxyvitamin D; vitamin D; weight loss.

Publication types

  • Comparative Study
  • Meta-Analysis
  • Review
  • Systematic Review

MeSH terms

  • Adiposity
  • Adult
  • Aged
  • Body Weight Maintenance / physiology*
  • Dietary Supplements
  • Female
  • Humans
  • Male
  • Middle Aged
  • Obesity / blood
  • Obesity / complications*
  • Vitamin D / administration & dosage
  • Vitamin D / analogs & derivatives
  • Vitamin D / blood*
  • Vitamin D / therapeutic use
  • Vitamin D Deficiency / blood
  • Vitamin D Deficiency / etiology*
  • Vitamin D Deficiency / prevention & control
  • Vitamins / administration & dosage
  • Vitamins / blood*
  • Vitamins / therapeutic use
  • Weight Loss / physiology*

Substances

  • Vitamins
  • Vitamin D
  • 25-hydroxyvitamin D