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.
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.
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 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.
Declaration: Selected authors declare potential conflicts of interest including published works, paid presentations and research grants for clinical trials. Refer to the paper for details. Separate to the present study, Dr Fuller has received research grants for clinical trials funded by SFI Research, manufacturers of herbal products.