The effects of Nigella sativa L. on obesity: A systematic review and meta-analysis

Ethnopharmacological relevance: Nigella sativa L. (N.sativa) is a traditional herbal medicine that has been used for centuries to treat rheumatoid arthritis, diabetes, asthma, and other metabolic disorders. Recently, anti-obesity characteristics of N.sativa have been indicated.

Aim of the study: The effects of N. sativa as a complementary therapy in obesity management remains controversial. We aimed to perform a meta-analysis on the effects of supplementation with N. sativa on some anthropometric indices in adult subjects.

Materials and methods: We searched PubMed/Medline, Cochrane Library, ISI Web of Science, and Scopus databases until June 2017 to identify relevant placebo-controlled clinical trials. Data was reported as weighted mean differences and standard deviations to show the magnitude of effects for N. sativa on body weight, body mass index (BMI) and waist circumference (WC).

Results: Findings of 11 studies revealed that N. sativa supplement reduced body weight (-2.11 kg, 95% CI: -3.61, -0.61, I²:72.4%), BMI (-1.16 kg/m²; 95%CI: -1.81, -0.51; I²: 40.1%) and WC (-3.52 cm, 95%CI: -4.10, -2.92, I² =0%) significantly compared to placebo groups.

Conclusion: Supplementation with N. sativa exerts a moderate effect on reduction in body weight, BMI and WC. However, due to the high heterogeneity for body weight and limited high quality studies, the findings should be declared by caution. No serious side effects were also reported following N. sativa supplementation. Further studies are needed to clarify the effects of N. sativa on other anthropometric indices.