If you’re taking herbal products for weight loss, you’re not only wasting your money, but also putting your health at risk.
The study — the first global review and meta-analysis of herbal medicines for weight loss in almost 20 years — found that although many studies report that people shed pounds using such products, the amount of weight lost is not clinically significant.
In addition, almost all the studies had serious design flaws that call into question even those modest weight-loss results. And safety data — particularly long-term data — on the herbal products were scarce.
“This finding suggests there is insufficient evidence to recommend any of these herbal medicines for the treatment of weight loss,” says Nick Fuller, the study’s senior author and an obesity researcher at Australia’s University of Sydney, in a released statement.
“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,” he adds.
Herbal supplements contain one or more plants as their primary ingredient. They come in various forms, including pills, powders and liquids.
“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 [drugstores],” Fuller points out.
Nor do supplement manufacturers have to prove the products are safe before they are sold to consumers. As I have noted before in Second Opinion, some weight-loss supplements sold online or in stores in the U.S. have been found to contain potentially harmful substances, including sibutramine, a drug that can increase blood pressure or heart rate, presenting a risk to people with a history of heart disease or stroke, and fluoxetine, an antidepressant that has been associated with such serious side effects as suicidal thinking, abnormal bleeding and seizures.
About one in seven American adults report having used a weight-loss supplement at some point in their lives.
Dozens of studies
For their review, Fuller and his co-authors analyzed data from 54 randomized clinical trials involving 4,331 healthy overweight or obese adults from a variety of countries and cultures.
The trials tested different kinds of weight-loss herbal supplements — ones containing the whole plant, not just oils from the plant — against placebos. The most common herbs used in the trials included Camellia sinensis (green tea), Garcinia cambogia (Malabar tamarind), Ephedra sinica (ma-huang), Phaseolus vulgaris (common bean) and Irvingia gabonesis (wild mango).
If there were four or more trials for a particular herb, Fuller and his colleagues pooled the data to conduct a meta-analysis.
Those meta-analyses showed that some herbal supplements had a statistically significant effect on weight loss compared to a placebo, but that the loss was less than 5.5 pounds and therefore not clinically significant.
In addition, most of the trials that reported the supplements led to weight loss tended to come from the same research groups, which “introduces a high risk of selective reporting and confirmation bias,” Fuller and his colleagues point out.
In fact, the researchers found that nearly all of the 54 trials were found to be at high risk of some kind of bias, primarily because of a failure to report full details about the herbal medicine being tested, as well as inadequate reporting on how the trial was designed and carried out.
Evidence on the supplements’ safety was also inadequate. As Fuller and his co-authors note, although the limited safety data in the 54 trials suggest the supplements are safe, other studies have raised warning flags.
Some recent research has found, for example, that the active chemical in Garcinia cambogia can cause liver damage. And in 2004, the Food and Drug Administration (FDA) banned the sale of weight-loss supplements containing ephedra after the herb was linked to heart attacks, strokes, seizures and heart rhythm problems — as well as several deaths. Since that ban, reported poisonings involving ephedra have fallen dramatically in the U.S., from 10,326 in 2002 to 180 in 2013, according to data from the National Poison Data System.
“It should be noted that rigorous collection and reporting of safety as required in phase III trials for pharmaceutical is not required prior to marketing herbal medicines, and so the safety of herbal medicines in general, with the exception perhaps of E. sinica, cannot be ascertained from the present review,” Fuller and his co-authors write.
Limitations and implications
As the researchers note, their review comes with its own limitations. Most notably, among the clinical trials it included were some that had people engage in other lifestyle interventions, such as dietary changes. That factor might explain why there was so little difference in weight loss between the intervention and placebo groups.
Also, the review included only studies in English-language publications — a factor that may limit the generalizability of the findings.
Still, Fuller and his colleagues believe the findings from this study — the most comprehensive on the topic in two decades — are clear.
“Currently there is insufficient evidence to recommend any of these herbal medicines for weight loss,” they conclude.
“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,” adds Fuller.
FMI: You can read the study in full on the website for Diabetes, Obesity & Metabolism.
Note: Although Fuller and four of his co-authors report no financial conflicts of interest, the study’s sixth author, Amanda Sainsbury, is not conflict-free. She has received research grants from various pharmaceutical companies. Australia’s National Health and Medical Research Council funded the current study, however.