Regular use of black seed oil lowers weight and reduces waist circumference
Many people who use black seed oil vouch that it works wonders for weight management and battling obesity, but what does the scientific evidence actually say?
Early evidence for the effects of black seed oil on weight was found in animal trials investigating the safety of black seed oil and it extracts. In one trial rats given black seed oil were noted not to gain weight compared to controls fed the same amount of calories. 
A human trial investigating the effects of Nigella sativa seed oil on obese men confirmed beneficial effects for weight loss.  Black seed oil was compared to placebo and given to two masked groups of overweight men aged between 30 – 50 for three months. The study recruited and included 39 in each arm. Participants were examined weekly. The results showed that the group receiving black seed oil had a statistically significant weight loss and reduction in waist circumference compared to placebo.
Participants were also assessed on a number of subjective symptoms (see table below), interestingly in the group taking black seed oil all subjective complaints disappeared after the first week. In the control group symptoms remained until the end of the study.
Black seed oil resulted in marked symptom improvement in treatment arm from week 1 which persisted to the end of the study. The placebo arm symptoms remained unchanged.
A previous study which looked at the effects of powdered black seed on body-mass index, waist-hip ratio, blood pressure, fasting blood sugar, serum lipids also confirmed a favourable impact of powdered N. sativa (black seed) seed in capsule was noted on almost all variables. The results of this study were not statistically significant because of small sample size. 
It is important to remember that consumption of powered seeds of Nigella sativa gives a much smaller dose compared to the oil which is essentially highly concentrated seed extract.
Another study which specifically looked at the metabolic impact of Nigella sativa power on menopausal women found no statistically significant changes in body weight, however improvements in total cholesterol, triglycerides, low density lipoprotein cholesterol, high density lipoprotein cholesterol and blood glucose was found.
In conclusion the clinical evidence supports the known anecdotal and other animal model trial evidence that black seed oil has benefits for weight loss. There is evidence that black seed oil has beneficial effect to counteract the adverse consequences of obesity. Further large scale trials are needed to establish exactly how much weight loss is achieved at each dose of black seed oil.
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2. Datau EA, et al. Efficacy of Nigella sativa on serum free testosterone and metabolic disturbances in central obese male. Acta Med Indones. 2010 Jul; 42(3):130-4.
3. Qidwai W, et al. Effectiveness, safety, and tolerability of powdered Nigella sativa (kalonji) seed in capsules on serum lipid levels, blood sugar, blood pressure, and body weight in adults: results of a randomized, double-blind controlled trial. J Altern Complement Med. 2009 Jun;15(6):639-44.
4. Ibrahim RM, et al. Protective Effects of Nigella sativa on Metabolic Syndrome in Menopausal Women. Adv Pharm Bull. 2014;4(1):29-33.