The first comprehensive review of complementary drugs (herbal and dietary supplements) for weight loss in 16 years – combining 121 randomized placebo-controlled trials involving nearly 10,000 adults – suggests that their use cannot be justified on the basis of in the current evidence.
The results of two studies presented at the European Obesity Congress (ECO) held online this year suggest that while some herbal and dietary supplements show a statistically greater weight loss than placebo, no it is enough to benefit health, and the authors say to get more research on its long-term safety.
Dietary and over-the-counter herbal supplements promoted for weight loss are becoming increasingly popular, but, unlike pharmaceutical drugs, no clinical evidence of their safety and effectiveness is required before they go on the market. Our rigorous evaluation of the best available tests shows that there is not enough evidence to recommend these weight loss supplements. While most supplements seem safe for short-term consumption, they will not provide clinically significant weight loss. “
Erica Bessel, lead author at the University of Sydney in Australia
The authors report on herbal supplements, which contain an entire plant or plant combinations as the active ingredient, and dietary supplements that contain natural compounds isolated from plants and animal products, such as fiber, fats, proteins, and antioxidants. They can be purchased as pills, powders and liquids.
Between 1996 and 2006, 1,000 dietary supplements for weight loss included in the Australian Register of Therapeutic Products were not evaluated. efficiency. Supplements may be sold and marketed to the public with sponsors (who import, export, or manufacture goods) who must have, but not necessarily, evidence to support their claims. Only 20% of new records are audited annually to ensure they meet the requirements. In some countries, the only requirement is that the supplements contain acceptable levels of non-medicinal products.
Estimates suggest that 15% of Americans trying to lose weight have tried a weight loss supplement, a $ 41 billion global industry by 2020. Despite its growing popularity, 16 years have passed since the latest review of the scientific literature on all herbs and dietary supplements.
Herbal medicines are not effective for losing weight
To provide more evidence, Australian researchers conducted a systematic review of all randomized trials comparing the effect of herbal supplements with placebo on weight loss, until August 2018. The findings were analyzed. data from 54 studies that included 4,331 healthy adults who were overweight or obese 16 years of age or older. Weight loss of at least 2.5 kg (5.5 pounds) was considered clinically significant. They also evaluated the design, reporting, and clinical value of the study.
The herbal supplements included in the analysis were: green tea; Garcinia cambogia and mangosteen (tropical fruits); White bean; ephedra (a stimulant that increases metabolism); African mango; yerba mate (herbal tea made from the leaves and twigs of the plant Ilex paraguariensis); velvet grapes (commonly used in traditional Indian medicine); licorice root; and East Indian Globe Thistle (used in Ayurvedic medicine).
The analysis found that only one agent, white kidney beans, resulted in statistically, but not clinically, greater weight loss than placebo (-1.61 kg; 3.5 lbs).
In addition, some combined preparations containing African mango, velvet grape, East Indian thistle and mangosteen showed promising results, but were investigated in three or fewer trials, often with poor methodology or research reports, and the results should be interpreted with caution, according to the researchers. to say.
Dietary supplements do not work to lose weight
A new systematic review to December 2019 also identified 67 randomized trials comparing the effect of dietary supplements containing naturally occurring isolated compounds with placebo for weight loss in 5,194 healthy overweight or obese adults (out of 16). years or more).
The dietary supplements included in the analysis were: chitosan (a complex sugar from the hard outer layers of lobsters, crabs, and shrimps that claims to block the absorption of fats or carbohydrates); glucomannan (a soluble fiber found in the roots of elephant yam, or konjac, which promotes the feeling of fullness); fructans (a carbohydrate composed of fructose chains) i conjugated linoleic acid (which claims to change body composition by decreasing fat).
The analysis found that chitosan (-1.84 kg), glucomannan (-1.27 kg) and conjugated linoleic acid (-1.08 kg) resulted in statistically significant weight loss, but not clinically, compared with placebo.
Some dietary supplements, including modified cellulose (vegetable fiber that expands in the stomach to cause a feeling of fullness) and blood orange juice extract, showed promising results, but were only investigated in one trial. and they need more testing before recommending them to lose weight. to say.
“Dietary and herbal supplements may seem like a quick fix to weight problems, but people need to be aware of how little we know about them,” says Bessell. “Very few high-quality studies have been done on some supplements with little data on long-term efficacy. In addition, many trials are small and poorly designed, and some do not report on the composition of supplements being The growth of the industry and the popularity of these products underscores the urgency of conducting more rigorous and larger studies to have a reasonable guarantee of their safety and effectiveness in weight loss. “