Insufficient evidence backing herbal medicines for weight loss

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There is currently insufficient evidence to recommend any of the herbal medicines examined in an Australian systematic review and meta-analysis.

Researchers at the University of Sydney led by senior author Dr Nick Fuller, says that 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 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 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. 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 Fuller.

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% of men and 19% 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, 1,000 dietary supplements for weight loss were listed on the Australian Register of Therapeutic Goods without evaluation of efficacy. 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% of new listings are audited annually to ensure they meet this requirement.

In some countries, the only requirement is that the supplement contains acceptable levels of non-medicinal substances.

“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 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.

Abstract
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.

Authors
Alison Maunder, Erica Bessell, Romy Lauche, Jon Adams, Amanda Sainsbury, Nicholas R Fuller

University of Sydney material

Diabetes, Obesity and Metabolism abstract

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