Review shows minimal evidence that dietary supplements lead to weight loss

June 23, 2021

Although Americans spend billions on them, published research shows a lack of strong evidence that dietary supplements and alternative therapies help adults lose weight, according to a new study published in Obesity, the flagship journal of The Obesity Society (TOS).

There are hundreds of weight-loss supplements like 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.

For the study, researchers completed a comprehensive review of 315 existing clinical trials of weight loss supplements and therapies, and most of the studies showed the supplements did not produce weight loss among users.

Dr. John Batsis

“Our findings are important for clinicians, researchers and industry alike, as they suggest the need for rigorous evaluation of products for weight loss,” said corresponding author John Batsis, MD, associate professor in the Department of Nutrition at the University of North Carolina Gillings School of Global Public Health and in the Division of Geriatric Medicine at the UNC School of Medicine. “Only then can we produce data that allows clinicians to provide input and advice with a higher degree of certainty to our patients.”

The evaluation should also be collaborative, with the supplement industry and academics working together to design high-quality clinical trials of weight loss supplements, Batsis added.

The paper’s authors explain that patients often struggle to lose or maintain weight, either because of a lack of efficacy of existing Federal Drug Administration (FDA)-approved therapies or a lack of access to health care professionals who provide treatments for obesity.

Even though the National Institutes of Health’s Office of Dietary Supplements has advanced the science of dietary supplements by evaluating information and stimulating and supporting research, members of TOS decided it was important to evaluate and perform a qualitative synthesis of non-FDA therapies to provide scientific evidence to guide its membership.

The research team conducted a systematic literature review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to evaluate the efficacy of dietary supplements and alternative therapies for weight loss in participants aged 18 and older. They performed searches of Medline (Pubmed), Cochrane Library, Web of Science, CINAHL and Embase (Ovid).

The researchers focused on 315 peer-reviewed, randomized-controlled trials and analyzed them for risk of bias, classifying 52 studies as having low risk of bias and being sufficient to support efficacy. Of these, just 16 studies demonstrated significant pre/post intergroup differences in weight compared with placebos. In the 16 methodologically distinct studies, weight loss ranged widely from 0.3 to 4.93 kilograms (0.7 to 10.9 pounds).

In a perspective written by members of TOS’s Clinical Committee — led by Srividya Kidambi, MD, with the Division of Endocrinology and Molecular Medicine at the Medical College of Wisconsin in Milwaukee, who also co-authored the paper — members recommend that clinicians consider the lack of evidence of non-FDA-approved dietary supplements and therapies and guide their patients toward tested weight-management approaches.

“Public and private entities should provide adequate resources for obesity management. We call on regulatory authorities to critically examine the dietary supplement industry, including their role in promoting misleading claims and marketing products that have the potential to harm patients,” the authors wrote.

The paper, titled “A Systematic Review of Dietary Supplements and Alternative Therapies for Weight Loss,” will be published in the July 2021 print issue. A perspective titled “Dietary Supplements and Alternative Therapies for Obesity: A Perspective from The Obesity Society’s Clinical Committee“ will accompany the paper.

Batsis’ research reported in this publication was supported in part by the National Institute on Aging of the National Institutes of Health (K23AG051681). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

The Obesity Society (TOS) is the leading organization of scientists and health professionals devoted to understanding and reversing the epidemic of obesity and its adverse health, economic and societal effects. Combining the perspective of researchers, clinicians, policymakers and patients, TOS promotes innovative research, education and evidence-based clinical care to improve the health and well-being of all people with obesity. For more information, visit www.obesity.org.

Contact the UNC Gillings School of Global Public Health communications team at sphcomm@unc.edu.