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Dietary Supplements for Weight Loss Lack Evidence, Research Suggests

Dietary Supplements for Weight Loss Lack Evidence, Research Suggests


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Key Takeaways

  • A meta-analysis of over 100 trials of herbal and dietary supplements found little proof of a substantial impact on health.
  • Although some participants saw modest weight loss, supplements are not linked to long-term success.
  • Other types of supplements may also have this problem, so shop wisely.

Dietary supplements that make weight-loss claims do not seem to have enough supporting evidence, according to a meta-analysis published in the journal Diabetes, Obesity and Metabolism.

Researchers reviewed 54 randomized, placebo-controlled trials of herbal and dietary supplements with approximately 4,000 participants who took options such as:

  • Green tea
  • White kidney bean
  • Ephedra
  • Yerba mate
  • Licorice root
  • Garcinia cambogia
  • Mangosteen
  • East Indian globe thistle

In another analysis, to be published later, the researchers looked at 67 other randomized trials representing about 5,000 participants that involved non-herbal options such as conjugated linoleic acid, chitosan, and glucomannan. These are soluble fiber and complex sugar products that manufacturers claim will promote feelings of fullness or block absorption of fat.

Weight loss of five pounds or above was considered clinically significant. Only white kidney bean supplements showed a notable amount of weight loss compared to a placebo—but even then, the difference did not meet the standard for clinical significance since the average amount of weight loss was about three pounds.

Regulatory Loopholes

The researchers evaluated whether any serious side effects occurred as a result of taking these supplements, and they were generally safe, says study co-author Erica Bessell, PhD candidate, of the Boden Collaboration for Obesity, Nutrition, Exercise and Eating Disorders at the University of Sydney in Australia. However, that doesn’t mean they were effective.

Erica Bessel PhD candidate

Unlike pharmaceutical drugs, which require rigorous testing and clinical evidence that demonstrates their safety and effectiveness, over-the-counter herbal and dietary supplements are not required to prove they work. In our research, it appeared that most supplements seem safe based on short-term usage, but they don’t provide any meaningful weight loss.

— Erica Bessel PhD candidate

The larger issue, she says, is that supplement-makers can make claims about weight loss as long as they include a disclaimer that the statement has not been evaluated by the Food and Drug Administration.

“Unlike pharmaceutical drugs, which require rigorous testing and clinical evidence that demonstrates their safety and effectiveness, over-the-counter herbal and dietary supplements are not required to prove they work,” she notes. “In our research, it appeared that most supplements seem safe based on short-term usage, but they don’t provide any meaningful weight loss.”

Like any type of drastic change to an eating plan, such as calorie restriction or dietary changes, you may see a degree of weight loss in the first week or two, which might make it seem like the supplement is working according to its claims. “These supplements might seem like a quick-fix solution to weight problems,” says Bessell. “That can be especially true if there’s considerable marketing.” But in terms of long-term effectiveness, that's just not the case.

Bold Claims and Scant Evidence Not Limited to Weight Loss Supplements

Bold claims and scant evidence are not only an issue with weight-loss supplements. One look through the supplement aisle will tell you that there are products geared toward athletic performance, sleep, hormone regulation, immune health, brainpower, and a plethora of other potential benefits.

So, how do you ensure your supplements will live up to their claims? Samantha Heller, MS, RD, exercise physiologist and clinical dietitian at NYU Langone Health, says there are a few strategies that can be helpful. The first is to look on the label for independent testing.

“Having a reputable third-party organization doing the testing is the minimum standard for a legitimate supplement producer,” she says.

Carol Aguirre, RD

Some supplements contain ingredients that food doesn't have. We don't know what those will do to our bodies over time, especially in combination. Then if you start stacking them together, you're increasing your risk, because there's no information about how these ingredients affect each other. So to call a product 'safe' is vague and meaningless at best, and at worst, deceptive.

— Carol Aguirre, RD

She suggests looking for testing done by ConsumerLab.com, NSF International, or US Pharmacopeia (USP). But, she adds, keep in mind that just because the supplement is certified as containing what's on the label, that doesn't mean it's "safe," or that are no risks of side effects.

"Some supplements contain ingredients that food doesn't have," she says. "We don't know what those will do to our bodies over time, especially in combination. Then if you start stacking them together, you're increasing your risk, because there's no information about how these ingredients affect each other. So to call a product 'safe' is vague and meaningless at best, and at worst, deceptive."

Another tip for vetting your supplements is to be cautious of big promises; especially phrases like “proven effective.” A particularly meaningless boast is “pharmaceutical strength,” says registered dietician Carol Aguirre, MS, RD, of Nutrition Connections.

“There's also no such thing as ‘pharmaceutical grade manufacturing,’ but we’ve seen that more often in the past few years,” she states. “It’s meant to give the impression that this supplement has a higher degree of production scrutiny." That doesn't mean a supplement manufacturer isn't following best practices for manufacturing. But comparing supplement production to the pharmaceutical industry is problematic and potentially misleading, says Aguirre.

In general, some people might find supplements helpful, but they can come with drawbacks and may not have substantial evidence backing up their claims.

What This Means For You

Some weight-loss supplements may offer modest benefits, but one of the largest studies to date on efficacy shows there simply isn't enough evidence to back up many manufacturers' claims.

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  1. Maunder, A, Bessell, E, Lauche, R, Adams, J, Sainsbury, A, Fuller, NR. Effectiveness of herbal medicines for weight loss: a systematic review and meta-analysis of randomized controlled trialsDiabetes Obes Metab. 2020;22(6):891-903. doi:10.1111/dom.13973