A wide range of complementary therapies is currently being promoted for reducing body
weight. Many patients perceive these therapies as easier to comply with than other interventions e.g. change in dietary lifestyle and exercise. While mainstream drugs for body weight reduction must demonstrate efficacy before receiving a license, food supplements do not need to meet this requirement. Few food supplements have therefore been submitted to clinical trials, and many health-care professionals are uncertain about their therapeutic value.
We undertook a systematic overview of the scientific literature to identify, summarize and critically evaluate systematic reviews of food supplements for body weight reduction. We conducted electronic searches in five databases to look for systematic reviews of specific (or combination) supplements for body weight reduction. We also searched the internet for conference proceedings and hand searched the bibliography of identified articles.
We identified 25 potentially relevant articles, and nine were included. The reviews evaluated the evidence from nine popular slimming supplements including chromium picolinate, Ephedra, bitter orange, conjugated linoleic acid (CLA), calcium, guar gum, glucomannan, chitosan and green tea. While some the included trials in the reviews had serious flaws in their methodology, three reviews did not formally assess the risk of bias for included studies. Overall, the results and conclusions of most of the systematic reviews did not indicate that the use of these supplements was associated with clinically significant reductions in body weight. Systematic reviews that reported a “statistically significant effect” are limited by small effect sizes (e.g., chromium picolinate), and/ or a high risk of adverse events (e.g., Ephedra).
The existing systematic reviews of weight loss supplements fail to provide convincing evidence that any of these preparations generate clinically relevant weight loss without undue risks. Until high quality trials emerge, and their efficacy (and safety) demonstrated, it does not seem appropriate to recommend them as weight loss aids. The result of this research was part of a press release at the 11th International Congress on Obesity at Stockholm, Sweden in July, 2010.
- Food supplements for body weight reduction: a systematic review of systematic reviews. Onakpoya IJ, Wider B, Pittler ME, Ernst E. Obesity (Silver Spring). 2011 Feb;19(2):239-44.
- The efficacy of Irvingia gabonensis supplementation in the management of overweight and obesity: a systematic review of randomized controlled trials. Onakpoya I, Davies L, Posadzki P, Ernst E. J Diet Suppl. 2013 Mar;10(1):29-38.
- Dietary supplements for weight loss. Onakpoya I, Ernst E. Kanarek RB, Lieberman HR (Eds) Diet, Brain, Behavior: Practical Implications. 2012. CRC Press, Florida, pp 153-167
Daily Mail – Weight loss supplements do not work, say experts.
Science Daily – No evidence that popular slimming supplements facilitate weight loss, new research finds.
The Telegraph – Weight food supplements ‘do not work’.
International Association for the Study of Obesity – New research finds no evidence that popular slimming supplements facilitate weight loss.