Insufficient evidence backing herbal medicines for weight loss

Summary: Study finds no statistical significance to show herbal supplements help with weight loss.

Source: University of Sydney

Researchers from the University of Sydney have conducted the first global review of herbal medicines for weight loss in 19 years, finding insufficient evidence to recommend any current treatments.

Senior author Dr Nick Fuller said with overweight and obesity rates reaching epidemic proportions worldwide, many people are turning to herbal supplements as an alternative approach to maintain or lose weight.

“The problem with supplements is that unlike pharmaceutical drugs, clinical evidence is not required before they are made available to the public in supermarkets or chemists,” said Dr Fuller from the University of Sydney’s Boden Collaboration for Obesity, Nutrition, Exercise and Eating Disorders based at its Charles Perkins Centre.

The systematic review and meta-analysis, published in Diabetes, Obesity & Metabolism, analysed the latest international research in this area finding 54 randomised controlled trials comparing the effect of herbal medicines to placebo for weight loss in over 4000 participants.

Results of the review and metanalysis

The research team found that despite some of the herbal medicines showing statistically greater weight loss than placebo, weight loss was less than 2.5kg and therefore not of clinical significance.

“This finding suggests there is insufficient evidence to recommend any of these herbal medicines for the treatment of weight loss. Furthermore, many studies had poor research methods or reporting and even though most supplements appear safe for short-term consumption, they are expensive and are not going to provide a weight loss that is clinically meaningful,” said Dr Fuller.

About herbal medicines for weight loss

The most recent data on the use of weight loss supplements, from a US study, showed that among people trying to lose weight 16 percent (12 percent of men and 19 percent of women) reported past-year use.

Herbal medicines, or ‘herbal supplements’ as they are commonly known, are products containing a plant or combinations of plants as the active ingredient. They come in various forms including pills, powders or liquids.

Common herbal supplements used for weight loss include green tea, garcinia cambogia, white kidney bean and African mango.

The authors write that between 1996 and 2006, 1000 dietary supplements for weight loss were listed on the Australian Register of Therapeutic Goods without evaluation of efficacy.

This shows herbal supplements

The research team found that despite some of the herbal medicines showing statistically greater weight loss than placebo, weight loss was less than 2.5kg and therefore not of clinical significance. Image is in the public domain.

These substances can be sold and marketed to the public with sponsors (those who import, export or manufacture goods) only required to hold, but not necessarily produce, evidence substantiating their claims. The authors note that only 20 percent of new listings are audited annually to ensure they meet this requirement.

“The growth in the industry and popularity of these products highlights the importance of conducting more robust studies on the effectiveness and safety of these supplements for weight loss,” said Dr Fuller.

The review excluded studies where the herbal medicine did not include the whole plant, was comprised of plant oils or combined with other dietary supplements such as fibres and proteins. This analysis will be reported in a future paper.

About this neuroscience research article

Source:
University of Sydney
Media Contacts:
Michelle Blowes – University of Sydney
Image Source:
The image is credited to Orozco Perez et al., eNeuro 2020.

Original Research: Open access
“Effectiveness of herbal medicines for weight loss: A systematic review and meta‐analysis of randomized controlled trials”. Nick Fuller et al.
Diabetes, Obesity & Metabolism doi:10.1111/dom.13973.

Abstract

Effectiveness of herbal medicines for weight loss: A systematic review and meta‐analysis of randomized controlled trials

Aim
To update the available evidence on the efficacy and safety of complementary medicines to assist in weight loss by conducting a systematic review and meta‐analysis of herbal medicines for weight loss.

Methods
Four electronic databases (Medline, Embase, CINAHL and Web of Science) were searched from inception until August 2018. A total of 54 randomized placebo‐controlled trials of healthy overweight or obese adults were identified. Meta‐analyses were conducted for herbal medicines with ≥4 studies available. Weight differences of ≥2.5 kg were considered clinically significant.

Results
As a single agent, only Phaseolus vulgaris resulted in a statistically significant weight loss compared to placebo, although this was not considered clinically significant. No effect was seen for Camellia sinensis or Garcinia cambogia. Statistically, but not clinically, significant differences were observed for combination preparations containing C. sinensis, P. vulgaris or Ephedra sinica. Of the herbal medicines trialled in ≤3 randomized controlled trials, statistically and clinically significant weight loss compared to placebo was reported for Irvingia gabonensis, Cissus quadrangularis, and Sphaeranthus indicus combined with Garcinia mangostana, among others, but these findings should be interpreted cautiously because of the small number of studies, generally poor methodological quality, and poor reporting of the herbal medicine interventions. Most herbal medicines appeared safe for consumption over the short duration of the studies (commonly ≤12 weeks). Some warrant further investigation to determine effect size, dosage and long‐term safety.

Conclusion
There is currently insufficient evidence to recommend any of the herbal medicines for weight loss included in the present review.

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