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Weight loss supplements: Global review


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A recent review finds limited evidence in favor of weight loss supplements. GOMBERT, SIGRID/Getty Images
  • Researchers have recently presented the results of the first global analysis in 19 years of clinical trials for weight loss supplements.
  • Drawing on two literature reviews, they found insufficient evidence to warrant the recommendation of supplements for weight loss.
  • The study’s authors drew their conclusions from 121 clinical trials involving nearly 10,000 participants.

According to the World Health Organization (WHO), obesity worldwide has nearly tripled since 1975. Alongside this trend, there has been an explosion in the sales of lightly regulated, under-researched herbal and dietary weight loss supplements.

About 15% of people in the United States have tried one of these dietary aids, the products of an industry valued at $140 billion in 2020.

The first global review in 19 years regarding the efficacy of herbal and dietary supplements for weight loss was recently presented by researchers from the University of Sydney (USYD) in Australia to the European Congress on Obesity (ECO).

The research, which encompassed two literature reviews including 121 randomized placebo-controlled trials involving over 10,000 participants with overweight or obesity, found insufficient evidence that herbal and dietary supplements produce clinically significant weight loss.

Erica Bessell, lead author of the study, 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.”

At issue are a range of pills, powders, and liquids marketed with the promise that they can help people lose weight. The products may include entire plants or products in which a plant is an active ingredient. They may also contain isolates from animal- and plant-based substances, such as fats, fiber, and protein.

“Over-the-counter herbal and dietary supplements promoted for weight loss are increasingly popular, but unlike pharmaceutical drugs, clinical evidence for their safety and effectiveness is not required before they hit the market,” said Bessell.

There is often little in the way of regulation to protect consumers from unproven claims. For instance, while the Food and Drug Administration (FDA) is responsible for the safety of dietary supplements once they become available on the market, prior to that, there is limited scope for FDA involvement.

The FDA states that “the law does not require the manufacturer or seller [of an herbal or dietary supplement] to prove to FDA’s satisfaction that the claim is accurate or truthful before it appears on the product.”

The first study involved a review of 54 trials that compared the effects of herbal supplements with those of placebos. The research involved 4,331 participants aged 16 years or above with overweight or obesity.

A weight loss of at least 5.5 pounds more than that achieved by a placebo was considered clinically meaningful.

The studies tested:

Only one of the substances — white kidney bean — produced a statistically significant benefit when tested as a single agent compared with placebo, although it still fell significantly short of the threshold for a clinical benefit.

Other supplements did produce statistically significant benefits when given in combination with other supplements, but, again, these benefits were not clinically significant.

In addition, the last four substances on the list above may have shown some promise for clinically significant weight loss. However, the authors of the study caution that each was tested in three trials at most and that those studies were characterized by substandard methodology and reporting.

The second analysis included 67 randomized trials testing the weight loss value of dietary supplements derived from naturally occurring compounds, compared with placebos. There were 5,194 adults with overweight or obesity partaking in these studies.

Chitosan, glucomannan, and conjugated linoleic acid produced statistically significant weight losses compared with placebo, but they were too small to be of clinical significance. Fructans, on the other hand, produced no statistically significant weight loss.

Two substances produced promising results: modified cellulose — which creates a sensation of being full — and blood orange juice extract. However, each was tested in just a single trial, which is not enough evidence to justify a recommendation for their use.

Bessell said:

“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. Very few high quality studies have been done on some supplements, with little data on long-term effectiveness. What’s more, many trials are small and poorly designed, and some don’t report on the composition of the supplements being investigated.”

There is also a fundamental issue with weight loss supplements, according to dietitian at Cleveland Clinic Kristin Kirkpatrick, who told Medical News Today,

“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.”

Learning to eat right is the key to long-lasting weight control, said Kirkpatrick, because, “[w]hile it’s not at all easy to lose weight in the first place, it surely is easier to lose it than to keep it off.”

The lack of rigorous study notwithstanding, people continue to purchase these dietary aids and depend on them for help in solving weight issues.

“The tremendous growth in the industry and popularity of these products,” said Bessell, “underscores the urgency for conducting larger, more rigorous studies to have reasonable assurance of their safety and effectiveness for weight loss.”



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