A large global review of herbal and dietary supplements for weight loss, combining 121 randomized controlled trials including nearly 10,000 adults, concludes that there is insufficient evidence that taking weight loss supplements are helpful.
The findings from two studies, presented at The European Congress on Obesity (ECO) held online this year, suggest that although some herbal and dietary supplements show statistically greater weight loss than placebo, the effect is not enough for meaningful clinical weight loss.
The Australian researchers call for more study into their long-term safety.
The first review
For the first analysis, Australian researchers reviewed 54 randomized trials, involving 4,331 healthy overweight or obese adults aged 16 years or older, that compared the effect of herbal supplements versus placebo on weight loss.
Weight loss of at least 2.5 kg (5.5 lbs) was considered clinically meaningful. The research team also evaluated study design, reporting, and clinical value.
Herbal supplements included in the analysis were:
- green tea
- Garcinia cambogia
- mangosteen (tropical fruits)
- white kidney bean
- ephedra (a stimulant that increases metabolism)
- African mango
- yerba mate (herbal tea made from the leaves and twigs of the Ilex paraguariensis plant)
- veld grape (commonly used in Indian traditional medicine)
- licorice root
- East Indian Globe Thistle (used in Ayurvedic medicine).
Dietary supplements don't work for weight loss
The analysis found that only one supplement, white kidney bean, resulted in a statistically, but not clinically, greater weight loss than placebo.
In addition, some combination preparations containing African Mango, veld grape, East Indian Globe Thistle and mangosteen showed promising results, but were investigated in three or fewer trials, often with poor research methodology or reporting, and the findings should be interpretated with caution, researchers say.
The second review of studies
A second review up if studies published to December 2019 identified 67 randomized trials comparing the effect of dietary supplements to placebo for weight loss in 5,194 healthy overweight or obese adults.
Dietary supplements included in this analysis were:
- chitosan (a complex sugar from the hard outer layers of lobsters, crabs, and shrimp that claims to block absorption of fat or carbohydrates)
- glucomannan (a soluble fibre found in the roots of the elephant yam, or konjac, that promotes a feeling of fullness)
- fructans (a carbohydrate composed of chains of fructose)
- conjugated linoleic acid (that claims to change the body composition by decreasing fat).
The analysis found that chitosan, glucomannan and conjugated linoleic acid resulted in statistically, but not clinically, significant weight loss compared to placebo.
"Herbal and dietary supplements might seem like a quick-fix solution to weight problems, but people need to be aware of how little we actually know about them", said the researchers. V
Very few high-quality studies have been done on some supplements with little data on long-term effectiveness. Many trials are small and poorly designed and, what’s more, some don't report on the composition of the supplements being investigated.
There is need for conducting larger and more rigorous studies to have reasonable assurance of their safety and effectiveness of these supplements for weight loss.
Source: 28th European Congress on Obesity, May 10-13, 2021.
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