Review of more than 300 clinical trials with products purported to facilitate weight loss found wide variability in risk of bias and data sufficiency suggesting caution among patients and physicians.
Strong evidence for the efficacy of dietary supplements to promote weight loss is extremely limited, according to results of a recent review of more than 315 clinical trials of supplements and alternative therapies that do not have FDA approval for weight reduction. The study appeared online June 23, 2021, in the journal Obesity.
The findings are important for patients with overweight or obesity and for clinicians, the investigators write, because the products are widely available, supported by unregulated marketing efforts, and currently used by an estimated 34% of Americans attempting weight loss.
Moreover, study authors, a number of them members of The Obesity Society, warn that “These products may indirectly undermine the value of guideline-driven obesity treatments.”
The systematic literature review of randomized controlled trials was led by John Batsis, MD, associate professor in the Division of Geriatric Medicine at the UNC School of Medicine and in the Department of Nutrition at the UNC Gillings School of Global Public Health.
The database search (Medline, Cochrane Library, Web of Science, CINAHL, and Embase) returned 20 054 citations; researchers reviewed 1743 full-text articles and just over 300 of those (315) were randomized controlled trials (RCT). In total those trials evaluated the efficacy of 14 “purported” dietary supplements, therapies, or a combination of these. Eligible trials were published in English and included patients with overweight or obesity who were aged ≥18 years.
Investigators elected, a priori, to present only dietary supplements or alternative therapies consisting of ≥5 RCTs.
Researchers found that risk of bias and sufficiency of data varied widely across the 315 RCTs included. Overall, 52 (16.5%) studies were classified as having a low risk of bias and sufficient to support efficacy of the product studied. Of these, 16 (31%) demonstrated significant pre/post weight changes compared to placebo. Weight loss also ranged significantly across those studies, from 0.3-4.93 kg. Among trials showing significant weight loss were 1 on chitosan, 1 on chromium, 5 on ephedra or caffeine, 2 on garcinia, 2 on green tea, and 1 on conjugated linoleum acid.
The high risk of bias and overall substandard nature of the studies is of concern, study authors point out, because many patients who struggle to lose weight or maintain weight loss have either had limited success with current FDA-approved therapies or do not have access to health care professionals who provide obesity treatment. These circumstances, they write, may prompt “a search for easily available nonprescription dietary supplements or alternative therapies” that will “satisfy consumers' and clinicians' desire for effective, low-risk, and low-cost options for achieving weight loss.”
"Our findings are important for clinicians, researchers, and industry alike as they suggest the need for rigorous evaluation of products for weight loss," said lead investigator Batsis in a statement from The Obesity Society. "Only then can we produce data that allows clinicians to provide input and advice with a higher degree of certainty to our patients."
In a perspective statement from The Obesity Society, authors underlined the need for clinicians and providers to be aware of the lack of evidence surrounding many of these supplements, despite unregulated claims related to efficacy.
“Our recommendation to clinicians is to consider the lack of evidence for 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. Finally, we call on regulatory authorities to critically examine the dietary supplement industry, including their role in promoting misleading claims and marketing products that have potential harm to patients,” wrote investigators.
Reference: Batsis JA, Apolzan JW, Bagley, PJ, et al. A systematic review of dietary supplements and alternative therapies for weight loss. Obesity. 2021;29:1102-1113.