The Effect of Vitamin D Supplementation on the Treatment of Overweight and Obesity: A Systematic Review of Randomized Controlled Trials

Numerous studies indicate that obese individuals have lower levels of vitamin D than humans with normal weight. Moreover, some in vitro studies demonstrated the role of vitamin D in weight reduction. However, both, obesity and vitamin D deficiency are major problems afflicting public health. The main purpose of this systematic review was to investigate the effect of vitamin D supplementation in decreasing the excessive body weight in overweight and obese patients, as evidenced in randomized controlled trials (RCTs). PubMed and EBSCO host were searched for articles. RCTs including overweight and adult participants supplemented with
vitamin D were eligible for inclusion in the current study. The outcome measures related to the body weight changes were considered (body weight [BW], Body Mass Index [BMI], waist circumference [WC], body fat [BF], muscle mass [MM]). The search strategy and study selection processes were performed according to the “PRISMA” guidelines. Seven studies were deemed as eligible for inclusion in the current study. One study showed that vitamin D treatment had a statistically
significant reduction in BW and WC. Also, three studies showed that BF was significantly reduced in the treatment group compared to the control group. Additionally, one study showed that the MM significantly increased in the treatment group compared to the control group whereas one other study showed that FFM was
significantly increased in the treatment group compared to the control group. The findings of the current analysis are still controversial since it is still difficult to determine which effects are due to vitamin D itself and which are mediated via calcium or other factors. The overall an impression is that vitamin D alone may affect fat mass and body mass distribution when supplement in overweight and obese people.