No clinically significant weight loss found for most herbal, dietary supplements
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Most herbal and dietary supplements do not promote a clinically significant weight loss in adults, according to data from two systematic reviews presented at the European Congress on Obesity virtual meeting.
“We conducted a systematic review of 121 randomized placebo-controlled trials investigating herbal medicines or dietary supplements containing isolated organic compounds for weight loss,” Erica Bessell, a PhD candidate in the Boden Collaboration, Central Clinical School, Faculty of Medicine and Health at the University of Sydney, told Healio. “Though most supplements were safe for use in the short term, very few were found to produce clinically meaningful weight loss. Those that were found to result in weight loss had only been investigated in one or two trials. Many trials were assessed to have a high risk of bias, and the design and conduct of the trials was often inadequately reported.”
No significant weight loss with dietary supplements
Bessell and colleagues presented data on 67 randomized placebo-controlled trials of dietary supplements containing isolated organic compounds for weight loss in adults with overweight or obesity. Four electronic databases were searched through December 2019. Meta-analyses were conducted for chitosan, glucomannan, conjugated linoleic acid and fructans. All studies compared the mean weight difference between participants receiving the dietary supplement with those receiving placebo.
In meta-analyses, participants taking chitosan (mean difference, –1.84 kg; 95% CI, –2.79 to –0.88; P < .01), glucomannan (mean difference, –1.27 kg; 95% CI, –2.45 to –0.09; P = .04) and conjugated linoleic acid (mean difference, –1.08 kg; 95% CI, –1.61 to –0.55; P < .01) had a statistically significant difference in weight loss compared with placebo. However, none of the dietary supplements met the study’s threshold of a 2.5 kg or greater weight loss for clinical significance. There was a borderline clinically significant weight difference between the intervention group and placebo for modified cellulose, manno-oligosaccharides among men, blood orange juice extract and three multiple-ingredient dietary supplements, but all of those products had an inadequate number of trials conducted for meta-analysis.
“Some of the supplements investigated in only one or two trials included in our systematic reviews warrant further research as the first results were promising,” Bessell said. “Future trials should be of the highest quality — randomized controlled trials — with improved methodology to reduce risk of bias.”
Herbals not linked to clinically significant weight loss
The findings from the dietary supplement systematic review were similar in a second systematic review examining the effects of herbal medicines containing extracts of whole plants for weight loss in adults with overweight or obesity. Researchers analyzed 54 randomized controlled trials comparing weight loss for participants who took an herbal medicine vs. placebo.
Of the single agents included in the meta-analyses, only adults taking Phaseolus vulgaris, or white kidney bean, had a statistically significant weight loss compared with placebo (mean difference, –1.61 kg; 95% CI, –1.96 to –1.26; P < .001). The finding did not meet the clinical significance of at least a 2.5 kg weight loss. There were statically and clinically significant weight losses observed with combination agents containing Irvingia gabonensis, or African mango; Ilex paraguariensis, or yerba mate; Cissus quadrangularis, or Veld grape; Glycyrrhiza glabra, or licorice root; and Sphaeranthus indicus combined with Garcinia mangostana, but all the agents had a small number of trials and generally poor methodological quality.
“As health professionals, we should be advocating for evidence-based care for our patients,” Bessell said. “The results of our systematic review highlight that taking herbal medicines or dietary supplements is not an effective weight-loss strategy. We would recommend that people trying to lose weight should save their money and seek out evidence-based care instead.”
References:
Bessell E, et al. Int J Obes. 2021;doi:10.1038/s41366-021-00839-w.
Maunder A, et al. Diabetes Obes Metab. 2020;doi:10.1111/dom.13973.
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Bessell E, et al. Effectiveness of dietary supplements for weight loss: A systematic review and meta-analysis of randomized placebo-controlled trials. Presented at: European Congress on Obesity Annual Meeting; May 10-13, 2021; (virtual meeting).
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