The study key point
- Researchers published recently the findings of the first global study of weight loss supplement clinical trials in 19 years.
- They found insufficient evidence to support the use of supplements for weight loss, based on two literature reviews.
- The authors of the study based their findings on 121 clinical trials affecting nearly 10,000 people.
Obesity has nearly tripled globally since 1975, according to the World Health Organization (WHO). Along with this trend, sales of lightly regulated, under-researched herbal and dietary weight loss supplements have exploded.
In the United States, about 15% of people have tried one of these dietary supplements, which are the products of a $140 billion industry by 2020.
Researchers from the University of Sydney (USYD) in Australia recently delivered the first global study on the effectiveness of herbal and dietary supplements for weight loss in 19 years at the European Congress on Obesity (ECO).
The study found insufficient evidence that herbal and dietary supplements cause clinically meaningful weight loss, based on two literature reviews that included 121 randomised placebo-controlled trials involving over 10,000 overweight or obese participants.
The study’s lead author, Erica Bessell, said:
“Our rigorous assessment of the best available evidence finds that there is insufficient evidence to recommend these supplements for weight loss. Even though most supplements appear safe for short-term consumption, they are not going to provide weight loss that is clinically meaningful.”
Not as well regulated as drugs
A variety of tablets, powders, and liquids are at problem, many of which claim to help people lose weight. Whole plants or products containing a plant as an active ingredient can be used in the products. They can also contain isolates of fats, fibre, and protein from both animal and plant sources.
“Over-the-counter herbal and dietary supplements that support weight loss are becoming more common, but unlike prescription drugs, clinical evidence for their safety and efficacy is not needed until they reach the market,” Bessell said.
Consumers are often exposed to unproven claims due to a lack of oversight. For example, although the Food and Drug Administration (FDA) is responsible for dietary supplement protection once they are available on the market, FDA involvement prior to that is minimal.
“The law does not require the manufacturer or seller [of a herbal or dietary supplement] to prove to FDA’s satisfaction that the argument is correct or true before it appears on the product,” according to FDA.
Herbal supplement trials
The first investigation looked at 54 trials that measured the effects of herbal supplements to placebos. A total of 4,331 people aged 16 and up who were overweight or obese took part in the study.
Clinical significance was described as a weight loss of at least 5.5 pounds greater than the placebo group.
The studies looked at:
- ephedra, a metabolism stimulant
- garcinia cambogia
- white kidney bean
- licorice root
- yerba maté, the herbal tea derived from the Ilex paraguariensis plant
- African mango
- veld grape
- East Indian Globe Thistle
Just one of the substances, white kidney bean, showed a statistically significant advantage as compared to placebo when tested as a single agent, but it fell well short of the clinical benefit threshold.
When given in conjunction with other supplements, other supplements produced statistically significant benefits, but these benefits were not clinically significant.
Furthermore, the last four substances on the list above may have demonstrated clinically meaningful weight loss potential. The study’s authors point out, however, that each was only studied in three trials at most, and that those tests were marked by poor methodology and reporting.
Trials of dietary supplements
The second study involved 67 randomised trials that compared the effectiveness of dietary supplements derived from naturally occurring compounds to placebos in terms of weight loss. The participants in these studies were 5,194 adults who were overweight or obese.
When compared to placebo, chitosan, glucomannan, and conjugated linoleic acid caused statistically significant weight loss, but the differences were too slight to be clinically significant. Fructans, on the other hand, did not result in a statistically significant reduction in body weight.
Modified cellulose, which causes a feeling of fullness, and blood orange juice extract also showed promising results. However, each was only studied in a single study, which is insufficient evidence to recommend their use.
Evidence in short supply
According to Bessell:
“While herbal and dietary supplements can seem to be a fast fix for weight issues, people should be mindful of how little we know about them. Some supplements have seen very few high-quality trials performed on them, and there is no evidence on their long-term efficacy. Furthermore, several trials are limited and poorly planned, and others do not report on the supplement compositions under investigation.”
According to Kristin Kirkpatrick, a dietitian at the Cleveland Clinic, there is also a basic problem with weight loss supplements.
“Supplements that may suppress appetite don’t actually teach you how to eat. Eventually, you will have to go off […] them, and when you do, you have essentially learned how to take a pill to control diet, but you have not actually learned what the right diet is for you based on genetics, lifestyle, etc.”
Kirkpatrick believes that learning to eat well is the secret to long-term weight loss because, “while it’s not easy to lose weight in the first place, it’s much easier to lose it than to hold it off.”
Despite the lack of objective research, people continue to buy these dietary aids and depend on them to help them lose weight.
“Growth in the industry and popularity of these items reinforces the need for larger, more systematic studies to provide fair assurance of their safety and efficacy for weight loss,” Bessell said.