Background This systematic review and meta‐analysis aimed to investigate the effect of cinnamon on body weight, body mass index (BMI), waist circumference (WC), waist–hip ratio (WHR), and body fat mass including the maximum number of studies. Methods Medline, ISI Web of Science, Scopus, Google Scholar, and Cochrane library were searched with no limitation from inception up to August 2019 for relevant randomized controlled clinical trials (RCTs). The RCTs' risk of bias was assessed using the Cochrane collaboration's tool. Random‐effects model was used for meta‐analysis. Results Twenty‐one RCTs with 1,480 participants were included. The meta‐analysis showed that cinnamon supplementation significantly reduces BMI [weighted mean difference (WMD) = −0.40 kg/m2, 95% confidence interval (CI): −0.57, −0.22 kg/m2, p < .001, I2 = 78.9%], body weight (WMD = −0.92 kg; 95% CI: −1.51, −0.33 kg; p = .002; I2 = 84.2%), and WHR (WMD = −0.02, 95% CI: −0.038, −0.018; p < 0.001; I2 = 0%). Cinnamon supplementation did not significantly affect the WC (WMD = −1.76 cm, 95% CI: −3.57, −0.045 cm; p = .056; I2 = 90.8%) and body fat mass (WMD = −0.87%, 95% CI: −1.87, 0.025%; p = .057; I2 = 78.6%). Conclusion Cinnamon supplementation significantly reduces body weight, BMI, and WHR. Future high‐quality long‐term RCTs are recommended to confirm these results.

Introduction: Hypertension is a chronic condition that might lead to renal and cardiovascular diseases. The previous trials examining the effect of cinnamon supplementation on blood pressure have led to conflicting results. The present systematic review aimed to summarize the effect of cinnamon supplementation on blood pressure using a meta-analysis of published randomized controlled clinical trials. Methods: To identify the eligible articles, MEDLINE, SCOPUS, ISI Web of Science, and Google Scholar were searched from inception until September 2019 for relevant articles. The risk of bias assessment was performed using the Cochrane collaboration tool. A Random-effects model was applied to calculate the summary effects. Results: Totally, 11 trials with 686 participants were included in this systematic review and meta-analysis. The dose of cinnamon supplement consumption varied from 500 to 10000 mg/d. The meta-analysis revealed that cinnamon supplementation significantly decreases systolic blood pressure (SBP) [WMD (weighted mean difference)= -5.72 mmHg, 95% confidence interval (CI): -8.63 to -2.80; P<0.001, I2= 81.1)] and diastolic blood pressure (DBP) (WMD= -4.06 mmHg, 95% CI: -6.68 to -1.44; P= 0.002, I2 = 88.6). Subgroup analysis suggested no significant reduction of DBP in subjects with diabetes (WMD= -2.015 mmHg, 95% CI: -4.55 to 0.52; P= 0.12, I2 = 72.3) and prediabetes or metabolic syndrome (WMD= -4.8 mmHg, 95% CI: -10.06 to 0.44; P= 0.073, I2= 92.5). Conclusions: Cinnamon supplementation could be beneficial in lowering SBP and DBP in adults. Further studies with different doses are recommended to confirm the present findings.