OPINION | Which herbal medicines can REALLY help you lose weight?

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There are currently only five American Food and Drug Administration (FDA)-approved medications for obesity management available in South Africa, one as an injectable drug and four in tablet form.

However, they are quite expensive and prescription-only medications and tend to be prescribed more for obese individuals with co-morbidities such as diabetes, in other words, people who are medically compelled to lose weight.

These drugs also have pronounced and unpleasant side effects. As a result, they are generally not available to or chosen by those of us who are interested in a simple yet successful way to drop one or two jeans sizes.

Off-the-shelf herbal medicines provide an attractive “natural” alternative to support our weight-loss efforts, spurred on by aggressive marketing of such products, but are these weight-loss claims actually backed up by real evidence?

Last year, a group of researchers from Australia took on the mammoth task to comb through four enormous online databases of medical publications to identify all of the placebo-controlled trials on herbal weight loss medicines conducted globally over the past 20 years, and to combine all of the data in one big meta-analysis.

Meaningful weight loss was defined as 2.5kg lost (which, we can all agree, is setting the bar pretty low). The herbs that were tested most frequently were Camellia sinensis (green tea), Garcinia cambogia, Phaseolus vulgaris (white kidney bean extract) and Ephedra sinica (also known as Chinese ephedra or Ma Huang).

For green tea, seven short-term intervention studies testing low to very high doses of green tea extract and its active component, EGCG, demonstrated no weight loss benefit. In five trials where green tea extract was combined with other active ingredients, average weight loss of less than 2kg was achieved.

Similarly, 11 trials found that that there was no weight loss benefit associated with short-term use of Garcinia cambogia, not as a single-herb extract and also not in combination with other active compounds. Seven trials testing white kidney bean extract at a variety of doses, either alone or in combination, also found no weight loss benefits.

Given the wide range of doses utilised in these trials, it is unlikely that there are doses of these three herbal medicines that would lead to effective weight-loss over the short term (1-3 months). On the plus side, these preparations appeared to be safe, and very few side-effects were reported.  

Side effects numerous

The same can unfortunately not be said for ephedra, the fourth-most tested weight-loss herb. Ephedra was tested in five trials, four of which were in combination with caffeine. Across large variations in the doses of both ephedra and caffeine, no clinically significant weight loss was observed, not even over a six-month period.

However, the side effects were numerous and disturbing, and included heart palpitations, increased blood pressure and gastro-intestinal troubles. These side effects can be attributed to the active ingredient ephedrine, which is a stimulant closely related to crystal methamphetamine (tik).

The added caffeine will also have contributed to these side-effects, especially the heart palpitations and digestive issues.

The weight loss properties of two local African herbs, veldt grape (Cissus quadrangularis) and African mango (Irvingia gabonensis) have also been tested, either separately or in combination, in four trials.

However, these trials were all performed by the same group of researchers in Cameroon, were of poor quality and sometimes reported massive reductions in food intake and weight loss of more than 25kg!

The Australian researchers therefore regarded these findings as dubious. South American yerba mate (Ilex paraguariensis) on its own had no effect on body weight in two trials, but in combination with other South American herbs achieved approximately 5 kg of weight loss over 45 days in a single trial.

When the supplementation was continued for 12 months, the initial weight loss was maintained, but unfortunately there was no further weight loss. Two trials in India also reported that a combination of East India globe thistle (Sphaeranthus indicus) and mangosteen (Garcinia mangostana) resulted in 3-4kg weight loss over 8-16 weeks.

Little supporting evidence

The Australian article also listed 18 herbs or combinations of herbs that have each been tested in only one trial. Only four of these 18 trials reported positive results, but with a maximum weight loss of only 3.5kg, which hardly seems worth the expense. And just for the record, no trials have been published on the effects of Rooibos on body weight in humans.

Apart from ephedra, all of these herbal medicines appeared to be safe at the doses tested and caused minimal adverse reactions, although some unpleasant gastro-intestinal side effects were noted in some trials. However, most of the trials were also quite short (less than four months), and so we have very little indication of what the effects of long-term habitual use of these herbal preparations will be.

We also have very little information on whether these products work better in certain gender, age or ethnic groups than in others.  

So, in summary, there are currently two kinds of herbal weight loss medicines: those that have been repeatedly tested and shown to not have any benefits for weight loss, and those that have not really been tested. Either way, manufacturers and advertisers of herbal medicines have little supporting evidence to back up their claims that these products can promote weight loss.

*Dr Hanél Sadie-Van Gijsen is affiliated with the Centre for Cardio-metabolic Research in Africa (CARMA) in the Division of Medical Physiology at the Faculty of Medicine and Health Sciences at Stellenbosch University.

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