UNC-Led Review Details Lack of High-Quality Evidence to Support Supplements, Alternative Therapies for Weight Loss

John Batsis, MD

A review of data from more than 315 clinical trials of weight loss supplements has returned results suggests very little strong evidence exists to support use of dietary supplements and alternative therapies as weight loss interventions in adults.

A systematic conducted by investigators at the University of North Carolina (UNC), results of the study suggest risk of bias and sufficiency varied widely across the studies examined and less than 17% of trials were considered to be of low risk of bias and sufficient to support efficacy.

"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 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, in a statement. "Only then can we produce data that allows clinicians to provide input and advice with a higher degree of certainty to our patients."

As the obesity epidemic continues to plague the US and other developed nations, the popularity of weight loss supplements and different dietary approaches has skyrocketed. With an interest in exploring claims of efficacy made by many manufacturers in the dietary supplement industry, Batsis and a team of colleagues sought to evaluate the current available evidence base related to use of these supplements and dietary approaches.

To do so, Batsis and colleagues designed the study as a systematic review of work assessing dietary supplements and alternative therapies for weight loss from within the Medline, Cochrane Library, Web of Science, CINAHL, and Embase databases. For inclusion in the review, studies needed to be designed as randomized clinical trials, published in English, contain patients with overweight or obesity, and examine a patient population 18 years of age or older.

A total of 20,504 records were identified in the investigators' initial query. After exclusion of duplicates and those not meeting inclusion criteria, 1743 full-text manuscripts were identified for assessment and 315 were ultimately included in the final review. These 315 examined 14 different types of dietary interventions, including calcium and vitamin D supplements, chitosan, chocolate/cocoa, green tea, guar gum, mind-body, and pyruvate.

Upon assessment, investigators found the risk of bias varied widely across the studies included in the review Overall, 52 (16.5%) studies were classified as having a low risk of bias. Of these, 16 (31%) demonstrated significant pre/post weight changes compared to placebo therapy. Investigators pointed out the weight loss observed in these studies was 0.3-4.93 kg. Trials demonstrating significant weight loss included 1 trial on chitosan, 1 on chromium, 5 on ephedra or caffeine, 2 on garcinia, 2 on green tea, and 1 on conjugated linoleum acid.

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.

This study, “A Systematic Review of Dietary Supplements and Alternative Therapies for Weight Loss,” was published in Obesity.