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The purpose of this paper is to propose a model for analysing the influence of costs of quality.

A model is designed by using a causal loop diagram and is analysed through a system dynamics approach. The model simulation is prepared by Vensim software.

Prevention and appraisal costs are the two effective cost factors. The model represented in this paper reveals that prevention costs have the most effect on total cost of quality and especially external failure costs. Hence, in order to achieve the customer expected quality level, prevention and appraisal costs should be considered.

Calculating and measuring non‐conformance costs is very difficult in organizations and some errors and mistakes may happen.

A system dynamics approach can analyse and measure the amount of prevention cost effects on cost of quality in different organizations.

The proposed methodology demonstrates the use of an innovative approach in developing a cost of quality concept and constructing a practical framework for system dynamics in a real case.

Garlic supplementation may be inversely contributed to body weight and composition; however, previous results have been inconsistent. This study aims to evaluate the effect of garlic supplementation on body weight and composition using a systematic review and meta-analysis.

Online databases of PubMed, ISI Web of Science, Scopus and Google Scholar were searched up to January 2020. The random-effects model was used to calculate the effect sizes of the included studies. The risk of bias of included studies was assessed using the Cochrane collaboration’s tool. Besides, the NutriGrade scoring system was applied to judge the credibility of the evidence.

In total, 18 studies (with 1,250 participants) were included in the meta-analysis. The pooled analysis revealed that garlic supplementation has a significant increase in body weight [weighted mean difference (WMD) = 0.31 Kg, 95% CI: 0.09, 0.53 Kg, P = 0.005, n = 12 effect sizes]. Waist circumference (WC) does remarkably reduce [WMD = −1.28 cm, 95% CI: −2.08, −0.47 cm, P = 0.002, n = 4 effect size]. However, body mass index, body fat percent and fat-free mass do not dramatically change (P > 0.05). Notably, the pooled analyses on body weight and WC were sensitive to two included studies. NutriGrade’s score was rated low for this meta-analysis.

Although garlic supplementation could slightly increase weight and simultaneously might decrease WC, these associations were not strong enough to corroborate the findings. Also, other anthropometric indices do not significantly change. Further well-designed randomized clinical trial studies are needed to confirm the results.