Supplement labels make big promises, but new science doesn't support them.

By Korin Miller
June 25, 2021
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It's hard to go anywhere online right now without being blasted with an ad for weight loss supplements. They pop up on social media and in paid ads on random web pages, promising that you'll lose a huge amount of weight in a short period of time just by taking one of these pills or powders.

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Credit: Getty Images

But despite the claims, a new study found that there's really no good evidence to suggest that many popular weight loss supplements actually work.

The study, which was published in the journal Obesity, was a systematic review of 315 randomized controlled trials-considered the gold standard in scientific research-that evaluated how well 14 dietary supplements worked. Of those, only 16 of the randomized controlled trials found evidence of significant weight changes (from 1-10 lbs.) in people who took supplements vs. a placebo during the study period.

Even then, the weight loss results were not consistent, and many studies had different results. Some studies would show a supplement was linked to weight loss, while others found it wasn't.

About 15% of adults in the US have used a weight-loss supplement at some point in their lives, according to the National Institutes of Health (NIH), with more women using these supplements than men. Americans spend about $2.1 billion a year on weight-loss supplements, the NIH says.

Lead study author John A. Batsis, MD, associate professor in the department of nutrition at the University of North Carolina at Chapel Hill, tells Health that his research team had "full objectivity" in looking at the supplements. The results, he says, "suggest that more high quality evidence is needed" before these supplements can be recommended to patients.

"Despite the large number of potential supplements available, this review does not support strong, high-quality evidence of the efficacy of any of these products," Dr. Batisis adds.

Here's what you need to know about the findings.

What are weight loss supplements, exactly?

A wide variety of weight loss supplements are available, and they all promise to help users drop pounds. These supplements come in capsules, tablets, liquids, powders, and bars, with manufacturers claiming the products reduce macronutrient absorption, appetite, body fat, and weight and increase metabolism and thermogenesis, per the NIH.

Common ingredients include botanicals, dietary fiber, caffeine, and minerals. However, the US Government Accountability Office says that "little is known about whether weight loss supplements are effective," noting that some supplements "have been associated with the potential for physical harm."

The US Food and Drug Administration (FDA) regulates dietary supplements, but the agency doesn't require that they be reviewed or approved by the FDA before they go on the market. Instead, companies that make supplements are responsible for determining that their products are safe and the claims on the label are true and not misleading.

Which weight loss supplements did the study look at?

There were 14 supplements overall:

  • chitosan
  • ephedra or caffeine
  • green tea
  • guar gum
  • garcinia cambogia
  • chocolate/cocoa
  • conjugated linoleic acid
  • white kidney bean
  • calcium plus vitamin D
  • chromium
  • hydroxycitrate
  • phaseolus
  • phenylpropylamine
  • pyruvate

What experts say about the study findings

They're not shocked by the results. "Many of these substances have not been well studied," Fatima Cody Stanford, MD, MPH, MPA, an obesity medicine physician and clinical researcher at Massachusetts General Hospital, tells Health. "When they are, many studies find what we see here-no significant weight loss."

Keri Gans, RD, author of The Small Change Diet, agrees. "This is 100% not surprising to me," she tells Health. "So many supplements make claims that unfortunately have no conclusive scientific research to back them up."

Given that these supplements aren't tightly regulated, Dr. Stanford is concerned about the potential that they could make people less healthy. "As an obesity medicine physician and scientist, I believe in using evidence-based medicine to help persons address their excess weight," she says. "The safety profiles of many substances that are utilized may lead to other health problems." There are also no dosage or safety measures to make sure that substances are well-regulated, Dr. Stanford says.

Relying on supplements alone can also mean that a person isn't engaging in other healthy lifestyle choices, Gans says. "Taking a supplement in hopes of achieving weight loss is not teaching an individual anything about creating healthy habits for long term success," she says. "Regular exercise and a well-balanced diet that includes plenty of fruits, veggies, 100% whole grains, monounsaturated fat may definitely help a person lose weight as well as achieve nutritional benefits. A supplement should never replace food and/or exercise."

If you're concerned about your weight and its potential impact on your health, Dr. Stanford recommends speaking to your health care provider about your options-not taking weight loss supplements. "Why venture down this path of potential poor outcomes when we have health care providers and a treatment paradigm that can help you to achieve and maintain a healthy weight?" she says.

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