Effects of oral Nigella sativa oil on the expression levels and serum concentrations of adiponectin, PPAR-γ, and TNF-α in overweight and obese women: a study protocol for a crossover-designed, double-blind, placebo-controlled randomized clinical trial

BACKGROUND: Obesity is a major public health problem in recent decades. The accumulation of excessive fat promotes inflammatory status. Meanwhile, herbal products are marketed for their weight-loss properties, such as Nigella sativa (N. Sativa) which has been used for centuries to treat rheumatoid arthritis, diabetes, and asthma; recently, the anti-obesity characteristics of N. sativa have also been indicated. However, the exact mechanisms and cellular-related pathways are still unclear. Thus, we will aim to assess the effects of oral N. sativa on the gene expression of inflammatory and adipogenesis-related factors, including TNF-α, PPAR-γ, and adiponectin as well as assessing their serum concentrations among obese and overweight individuals. METHODS: Obese and overweight women aged 25–55 years with a body mass index (BMI) of 25–35 kg/m(2) will be recruited from the Obesity Clinic in Shahid Sadoughi University of Medical Sciences and will be assessed for eligibility against inclusion criteria. They will be randomly assigned into two groups to receive either two capsules of N. sativa or two capsules of placebo per day for eight weeks (each capsule contains 1000 mg of N. sativa or placebo). There will be a four-week wash-out period and then participants will receive the reverse supplements for another eight weeks. Biochemical assessments and gene expressions (using real-time polymerase chain reaction) will be conducted at the beginning and at the end of every intervention period. DISCUSSION: The present study will investigate the probable cellular pathways for the anti-obesity effects of N. sativa in overweight/obese women. TRIAL REGISTRATION: Iranian Registry of Clinical Trials, IRCT20180528039884N1. Registered on 2nd of July, 2018. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s13063-019-3568-0) contains supplementary material, which is available to authorized users.