There are numerous trials reported the effect of ALA on obesity measurements; while no summarized dose-response meta-analysis is available to address the effects of dose and duration of ALA supplementation on obesity measurements. We aimed to summarize the results of studies evaluating the effects of ALA supplementation on obesity measurements in a systematic review and dose-response meta-analysis.
In a systematic search from Scopus, PubMed, Embase, Proquest electronic databases up to January 2020 relevant studies were retrieved. Randomized, placebo-controlled trials investigating the effect of ALA supplementation on obesity measurements including weight, body mass index (BMI), waist circumference (WC), waist to hip ratio (WHR) and fat mass (FM) were included. Two class and dose-response meta-analysis were performed to data analysis.
Totally, eighteen, twenty one and eight studies were included for the meta-analysis of ALA-weight, ALA-BMI, ALA-WC respectively. In the two-class meta-analysis, ALA treatment significantly reduced weight (WMD: -2.29 kg, 95% CI: -2.98, 1.60, P <0.01) and BMI (WMD: -0.49 kg/m2 , 95% CI:-0.83,-0.15, P=0.005) but no effect on WC (WMD: -2.57 cm, 95% CI: -8.91, 3.76; P=0.426). While the dose-response meta-analysis revealed that the duration of ALA treatment is a significant factor affecting WC reduction (P non-linearity =0.047). While no evidence of departure from linearity was observed for other variables; moreover, subgrouping also revealed that gender could be an important factor affecting the ALA impact on WC which was significant among women (WMD: -4.099; CI: -7.837, -0.361; P=0.032).
According to our finding, ALA treatment significantly reduced BMI, weight in a two-class meta-analysis without evidence of departure from linearity in terms of dose or duration. While the association of ALA treatment on WC is dependent to the duration of the study. Although further trials evaluating the other obesity measurements specially central obesity will be helpful to infer a more reliable result.