Efficacy of vitamin D alone or in combination with weight-reduction programs in weight loss among adults with above-normal BMI: a systematic review and meta-analysis
Authors: Guevara J R B , Velilia A R , Tiu S A K , Ti A C , Tinio K A F , Torres A Y B , Tumpalan J J D , Tungal P F , Tupaz I Y , Villamor J F A , Vinzon M C M , Virtucio L M S , Vocal I C S , Vollinger C M T , Yanez P L C ,   Group under Dr. Maria Teresa Tolosa
Published: October 2021

Abstract

Introduction
The impact of Vitamin D supplementation on weight loss has been demonstrated in several randomized controlled trials (RCT), but there is still lack of consensus regarding its efficacy. This study aims to assess the efficacy and safety of Vitamin D in weight reduction in terms of changes in weight loss, BMI, neck circumference, mid-upper arm circumference, waist circumference, waist-thigh ratio, waist-to-hip ratio, and percent body fat, as well as reported adverse effects.

Methodology
MEDLINE (PubMed), Google Scholar, WHO database, Herdin, Cochrane Database and EMBASE were searched for literature published from 2005–2020. A systematic search was conducted for RCTs on the efficacy of Vitamin D (alone or in combination with Calcium, or with a weight-loss program, or with both) in weight loss among participants 18–75 years old with above-normal BMI, and with a study duration of 4–12 weeks. Sixteen RCTs were included in this systematic review and meta-analysis. Screening and selection were based on the eligibility criteria, while appraisal included checking for the risk of bias, assessing the validity of the results of the study, and its methodological quality. Outcomes of eligible studies were obtained directly from the studies, if available, or summarized and calculated from the available data. For continuous data, mean differences were compared.

Results
When compared with placebo, Vitamin D supplementation showed a significant reduction in weight loss (mean difference [MD] = −0.92; 95% confidence interval [95% CI], −1.52 to −0.31; P=0.003), BMI (MD = −0.52; 95% CI: −0.73 to −0.31; P=0.02), waist circumference (MD = −1.35; 95% CI: −2.21 to −0.33 P=0.0006) and percent body fat (MD = −0.82; 95% CI; −1.40 to −0.25; P=0.005) but no significant effect on reduction of waist-to-hip ratio (MD = −0.01, 95% CI; −0.01 to 0.00; P=0.17). None of the studies reported outcomes for neck circumference, mid-upper arm circumference, and waist-thigh ratio. Heterogeneity was addressed using random effects model in analysis. Out of the 16 studies included, only two reported adverse events, which include constipation after intake of Vitamin D and calcium supplements and other multiple non-serious adverse events.

Conclusion and recommendations
Vitamin D as an adjunct showed a significant effect on weight loss, BMI reduction, decrease in waist circumference and percent body fat among adults after a short-term intake of oral Vitamin D, thus Vitamin D supplementation may be recommended as an adjunct treatment for weight loss among adults, but the study results should be used with caution as significant heterogeneity was observed. Further conduction of local RCTs and meta-analysis is recommended for further elucidation of data in order to determine its efficacy among Filipinos.

Funding Acknowledgement
Type of funding sources: None. Effect of Vit D on waist circumference