Few high-quality studies published on dietary supplements, therapies for weight loss
Most studies on dietary supplements and alternative therapies for weight loss are considered low quality due to small sample size, short follow-up and poor design, according to findings from a systematic review and meta-analysis.
“Despite the large number of potential supplements available, this review does not support strong, high-quality evidence of the efficacy of any of these products as a result of the heterogeneity in study methods,” John A. Batsis, MD, a geriatrician at UNC Health and associate professor of medicine and nutrition at the University of North Carolina at Chapel Hill, told Healio. “Clinical providers should rely on evidence-based interventions to support weight loss, such as behavioral weight-loss interventions, medications or bariatric surgery. Providers now have evidence to provide to their patients that there are methodological challenges in suggesting efficacy of such supplements.”
Batsis and colleagues conducted a systematic review and meta-analysis of studies evaluating the efficacy of weight loss with dietary supplements and alternative therapies published in MEDLINE, Cochrane Library, Web of Science, CINAHL and Embase. Researchers included peer-reviewed randomized controlled trials focused on intentional weight loss in adults with overweight or obesity. The Cochrane Collaboration’s risk-of-bias tool was used to evaluate study quality.
The meta-analysis included 315 randomized controlled trials. At least five randomized controlled trials were available for 14 dietary supplements or alternative therapies: acupuncture, calcium and vitamin D, chitosan, chocolate/cocoa, chromium, ephedra or caffeine, garcinia or hydroxycitrate, green tea, guar gum, conjugated linoleic acid, mind-body interventions, Phaseolus, phenylpropylamine and pyruvate.
Of the 315 studies, 52 were classified as low risk and sufficient to support efficacy. The number of low-bias studies varied by therapy. Of 45 randomized controlled trials of acupuncture, only two were considered low bias. For calcium and vitamin D, five of 22 randomized controlled trials were labeled as low bias. Ten of 31 studies of ephedra or caffeine were low bias, 16 of 38 green tea trials were considered low bias, five of 31 studies of conjugated linoleic acid were considered low bias, and two of 22 mind-body interventions were labeled as low bias.
Of the 52 low-bias studies in the meta-analysis, 16 noted a significant difference in weight post-intervention compared with pre-intervention. There were significant differences in weight observed in five ephedra or caffeine studies, two garcinia and hydroxycitrate studies, two green tea studies, and one study each on chitosan, chromium and conjugated linoleic acid. The remaining dietary supplements or alternative therapies had no low-bias studies showing a significant intergroup weight difference post-intervention compared with pre-intervention.
Batsis said the findings reveal a large need for high-quality trials on dietary supplements and alternative therapies for weight loss.
“The importance of an academic-industry partnership is critically necessary to determine efficacy of each category and to ensure studies are free of the potential for commercial bias,” Batsis said. “Longer duration trials and larger sample sizes are also needed. Our evaluation highlights the importance of the efforts put forth by the Office of Dietary Supplements to advance the science of nutritional supplementation and a need for high-quality research. Having a partnership between researchers, funders and industry is critically needed. A well-designed clinical trial is challenging and requires key stakeholders and experts in this process. Such methods are used in other domains and diseases to assert effectiveness.”
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John A. Batsis, MD, can be reached at firstname.lastname@example.org.