Obesity Society review finds only 16 of 315 supplement trials showed weight loss
A review of 315 trials found only 16 in which a supplement beat placebo, with weight differences no larger than 4.93 kilograms, which is useful context for anyone weighing marketing claims.
Adults looking for a supplement to lose weight have little rigorous research to lean on, according to a systematic review published in Obesity, the journal of The Obesity Society. Of 315 randomized controlled trials of dietary supplements and alternative therapies, just 16 showed a significant weight difference from placebo, and those differences ranged from 0.3 to 4.93 kilograms [2].
The researchers limited their review to peer-reviewed trials in people 18 and older. They rated 52 of the 315 studies as low risk of bias and adequate to support a conclusion about efficacy. Within that group, 16 showed significant between-group weight differences. The authors described those 16 studies as methodologically distinct [2].
John Batsis, MD, is the corresponding author. He is an associate professor in the Division of Geriatric Medicine at the University of North Carolina School of Medicine, in the Department of Nutrition at the UNC Gillings School of Global Public Health, and a faculty fellow at the Carolina Population Center [2]. In the paper, he and his colleagues wrote that most of the trials they examined found no weight loss among users of the products [2].
The search covered Medline (PubMed), the Cochrane Library, Web of Science, CINAHL and Embase (Ovid), and the team followed PRISMA reporting standards for systematic reviews [2].
The category is broad. Hundreds of weight-loss supplements are on the market, including green tea extract, chitosan, guar gum and conjugated linoleic acid, and an estimated 34% of Americans who are trying to lose weight have used one, according to the paper [2]. Americans spend billions of dollars on them, the authors wrote, while the published evidence for real benefit remains thin [2].
Batsis said rigorous evaluation of these products is needed so that clinicians can "provide input and advice with a higher degree of certainty to our patients" [2]. He added that the work should be collaborative, with supplement makers and academic researchers designing high-quality trials together [2].
A perspective from The Obesity Society's Clinical Committee, led by Srividya Kidambi, MD, MS, of the Division of Endocrinology and Molecular Medicine at the Medical College of Wisconsin in Milwaukee, accompanied the review. Its authors advised clinicians to consider the weak evidence behind non-FDA-approved supplements and therapies and to point patients toward weight-management approaches that have been tested [2]. They also called on regulators to "critically examine the dietary supplement industry," including its role in "promoting misleading claims and marketing products that have the potential to harm patients" [2].
Why it matters for patients
The largest weight difference in the positive group of studies was 4.93 kilograms, about 11 pounds, while the smallest was 0.3 kilograms, roughly two-thirds of a pound [2]. The published materials do not name which supplements or therapies produced those results, and the review does not break out findings product by product [2].
Dietary supplements are not FDA-approved drugs, and the review covered only non-FDA-approved supplements and alternative therapies. It did not assess prescription weight-loss medicines, and no comparison between supplements and prescription treatment appears in the published materials [2].
The paper's authors also noted why patients often turn to these products: some people do not get enough benefit from FDA-approved obesity therapies, and others cannot reach a clinician who treats obesity [2].
The review lists financial relationships involving several authors, including equity in a remote-monitoring startup, funding from a food company to investigate topics from the manuscript, and consulting or speaking fees from Novo Nordisk, AstraZeneca, Unjury and Medifast [2]. The Obesity Society provided no funding for the work [2].
What happens next
The review, titled "A Systematic Review of Dietary Supplements and Alternative Therapies for Weight Loss," appeared in the July 2021 print issue of Obesity, with the Clinical Committee perspective published alongside it [2]. Whether the collaborative trials Batsis described are being planned has not been reported [2].
Sources
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