March 02, 2020
In the first global review of herbal weight-loss supplements in almost two decades, investigators found there was insufficient evidence to recommend any of these "medicines" for this purpose.
"There was no evidence to suggest people should be taking herbal medicines for [clinically meaningful] weight loss," study investigators Erica Bessel, MND, and senior author Nicholas R. Fuller, PhD, both from the University of Sydney, Australia, told Medscape Medical News via email.
The study findings suggest "healthcare practitioners should continually prompt their patients regarding any over-the-counter weight loss medications they are taking, so they can steer them towards evidence-based care," they added.
Overweight and obesity have reached epidemic proportions worldwide, with the global prevalence doubling since 1980.
For individuals who are unable to lose a satisfactory amount of weight with lifestyle interventions there are currently five prescription weight-loss drugs approved by the US Food and Drug Administration (FDA), three of which have also been approved by the European Medicines Agency and Australian Therapeutic Goods Administration.
The addition of these approved agents to lifestyle interventions increases weight loss but some patients avoid or stop taking these drugs because of side effects and costs.
Many individuals turn to over-the-counter supplements, which are cheaper, easier to access, and may have fewer side effects, the investigators note.
A recent study reported that 16.1% of individuals in the United States who were trying to lose weight had used a weight-loss supplement in the past year.
However, despite the large number of herbal weight loss supplements on the market, few are supported by robust scientific safety and efficacy data.
Not Clinically Significant
To update the available evidence of these supplements, the investigators conducted a systematic review and meta-analysis of herbal medicine for weight loss.
The study included data from 54 randomized placebo-controlled trials of herbal weight-loss medicines conducted in 4331 overweight or obese adults in countries around the world that lasted 12 weeks or less.
Common herbal supplements included in the studies were:
- Green tea (12 studies)
- Malabar tamarind (11 studies)
- White kidney bean (seven studies)
- Ephedra (five studies)
- African mango (three studies)
- Yerba mate (three studies)
- Veld grape (two studies)
- Licorice (two studies)
- Mangosteen (two studies)
- Miscellaneous herbal medicines (17 studies)
In addition, some of the trials investigated a product that contained more than one of these herbs.
Only one study examined traditional Chinese medicine (RCM-104), and three others looked at traditional formulas from Japan (Bofu-Tsusho-San), Korea (Taeeumjowi-tang), and Iran (Triphala).
Although some supplements were associated with a statistically significant difference in weight loss compared with placebo, the weight loss was less than 2.5 kg and therefore not considered clinically significant.
In fact, only one single agent, white kidney bean, resulted in a statistically, but not clinically, significant difference in weight loss compared with placebo.
There were also statistically, but again not clinically, significant weight loss differences with some combination preparations.
Poor Methodology, Poor Reporting
Statistically and clinically significant weight loss was reported for some products that were studied in three or fewer trials, but the investigators note these findings require cautious interpretation because of the small number of studies, poor methodology, and poor reporting of herbal medicine interventions.
The analysis showed most herbal medicines appeared safe for consumption over the short duration of the studies.
However, they also point out that herbal medicines are not subject to the same rigorous safety data collection and analysis as pharmaceutical agents, and therefore the safety of herbal supplements can't be determined by the current review.
In fact, the investigators note that ephedra can lead to pronounced cardiovascular and central nervous system stimulating effects and that, in 2004, the FDA banned its use in supplements and several other countries restricted its use.
"Some herbal medicines warrant further investigation in larger more rigorous studies to determine the effect size, dosage, and long-term safety," the investigators note.
Future randomized placebo-controlled studies of herbal supplements for weight loss would benefit from trial registration and ensuring studies are conducted and reported in a way that minimizes bias, the investigators add.
The research was supported by the National Health and Medical Research Council of Australia.
Fuller is the author of Interval Weight Loss and Interval Weight Loss For Life and has received research grants for clinical trials funded by SFI Research, the Australian Eggs Corporation, Sanofi-Aventis, Novo Nordisk, Allergan, Roche Products, MSD, and GlaxoSmithKline. Coauthor Amanda Sainsbury, University of Sydney, is the author of The Don't Go Hungry Diet and Don't Go Hungry For Life, and reports she has provided paid presentations at conferences for Eli Lilly, Pharmacy Guild of Australia, Novo Nordisk, Dietitians Association of Australia, Shoalhaven Family Medical Centres, Pharmaceutical Society of Australia, and Metagenics, and has served on the Nestlé Health Science Optifast® VLCD™ advisory board. Bessel, Maunder, and the other review authors have reported no relevant financial disclosures.