Weak Evidence for Weight Loss in the 'Wild West' of Supplements

"Purported" weight-loss products — 12 dietary supplements and 2 alternative therapies — lack high-quality evidence to back up claims of efficacy, a systematic review by the Obesity Society reports.

Most of the more than 300 published randomized controlled trials in the review were small and short, and only 0.5% found a statistically significant weight loss of up to 5 kg, John A. Batsis, MD, from the University of North Carolina at Chapel Hill, and colleagues reported in the journal Obesity.

"Despite the poor quality of these studies with high degrees of bias, most still failed to show efficacy of the product they were testing," Srividya Kidambi, MD, from the Medical College of Wisconsin, Milwaukee, and colleagues from the Obesity Society's Clinical Committee pointed out in an accompanying commentary.

"Yet these are the studies that are often used to support manufacturers' claims of 'clinically proven' in their marketing," they noted.

Most consumers, they continued, are unaware that these nondrug weight-loss products are not regulated by the Food and Drug Administration, but rather, if their ingredients are "generally regarded as safe," they are treated as dietary supplements and require little or no testing to show either efficacy or safety.

"Our patients need to become aware that dietary supplements for weight loss are nothing more than a pipe dream, and as clinicians we would do well to talk with our patients and help steer them toward science-based treatments rather than the 'Wild West' of dietary supplements that are marketed for weight loss," Scott Kahan, MD, MPH, coauthor of the review and commentary, told this news organization.

The dietary supplement industry has a strong lobby against legislation for more rigorous requirements for claims, noted Kahan, of the National Center for Weight and Wellness as well as George Washington University, Washington.

However, "there has to be some level of protection for consumers" who are faced with ads by "healthy skinny people saying this [product] can change your life."

Clinical providers need to guide patients to "evidence-based interventions to support weight loss such as behavioral weight-loss interventions, [FDA-approved] medications, or bariatric surgery," said Batsis, who also coauthored the commentary.

There is a "critical need" for more rigorous trials, and a partnership between researchers, funders, and industry, he added.

According to Kidambi and colleagues, "the use of these products will continue as long as they are allowed to be marketed with the aforementioned limited federal oversight and there is a lack of access to evidence-based obesity treatments."

The commentary authors "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."

They also urged public and private health insurance plans to "provide adequate resources for obesity management."

And clinicians should "consider the lack of evidence for non-FDA–approved dietary supplements and therapies and guide their patients toward tested weight-management approaches."

Subpar Evidence, Booming Industry

"Annual sales of dietary supplements for weight loss are booming with an industry valued at $30 billion worldwide, despite subpar evidence" of efficacy, the commentary authors wrote by way of background.

After the Dietary Supplement Health and Education Act of 1994, the National Institutes of Health's Office of Dietary Supplements was established "to strengthen the knowledge and understanding of dietary supplements by evaluating scientific information, stimulating and supporting research, and educating the public," they explained.

However, dietary supplements and alternative therapies are endorsed by influencers and celebrities and marketed as a panacea for obesity and weight gain.

Literature Review Finds Scant Evidence

Consumers may believe that the "clinically proven" claims of efficacy of these "natural" weight-loss treatments have been thoroughly evaluated for safety and efficacy by the FDA, and clinicians lack information to counsel patients about this.

Therefore, although the Office of Dietary Supplements' work has importantly advanced the science, the review authors wrote, members of the Obesity Society believed it was important to evaluate and perform a qualitative synthesis of the evidence for efficacy of non-FDA–regulated weight-loss supplements and alternative therapies to better inform clinicians and consumers.

From more than 20,000 citations of 53 dietary supplements and alternative therapies promoted for weight loss, the researchers identified 314 randomized controlled trials of 14 products that each had at least 5 randomized controlled trials.

The two types of alternative therapies in the review were mind-body interventions – which included behavioral therapies (for example, mindfulness and stress management), hypnosis, meditation, or massage – and acupuncture.

Several popular and widely used products (for example, human chorionic gonadotropin, raspberry ketones, nicotinamide adenine dinucleotide, vitamin infusions) did not meet the predefined number of published randomized controlled trials to be eligible for inclusion in the review.

The greatest number of trials were for acupuncture (45 trials), green tea (38), conjugated linoleic acid (31), ephedra with or without caffeine (31), mind-body therapies (22), and calcium and vitamin D (22). There were fewer trials of garcinia and/or hydroxycitrate (15), chitosan (9), phaseolus (7), pyruvate (7), chocolate/cocoa (6), chromium (6), guar gum (5), and phenylpropylamine (5).

Of the 314 studies, only 52 studies (16.5%) demonstrated that the products were efficacious and low risk, and only 16 studies (0.5%) reported a statistically significant between-group weight loss (0.3-4.93 kg).

For more information, in addition to their review and commentary, the authors refer clinicians to a dietary supplement label database.

The study was supported in part by grants from the National Institute on Aging. Batsis reported equity in SynchroHealth. Kidambi reported being the medical director for TOPS Center for Metabolic Health at the Medical College of Wisconsin, which is supported by TOPS. Kahan reported serving as a consultant for Novo Nordisk, Vivus, Gelesis, and Pfizer.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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