No 'high-quality' evidence that weight loss supplements work

• Researchers conducted a systematic review of randomized controlled trials of a selection of weight loss supplements and alternative therapies.
• They found no high-quality evidence of the efficacy of any of the products reviewed.
• An accompanying opinion piece calls for closer scrutiny of the supplement industry and its role in promoting “misleading claims” about products.
• The Council for Responsible Nutrition, which represents the supplement industry, has questioned the validity of this latest research.

Among adults in the United States trying to maintain a moderate weight, roughly a third say they have used dietary supplements to achieve their goal.

But, according to a new review, high-quality evidence of the benefits of many weight loss products and alternative therapies is currently lacking.

The systematic review of randomized controlled clinical trials — the gold standard of clinical research — appears in the journal Obesity.

“Our findings are important for clinicians, researchers, and industry alike, as they suggest the need for rigorous evaluation of products for weight loss,” says corresponding author John Batsis, M.D., of the University of North Carolina School of Medicine, Chapel Hill.

“Only then can we produce data that allows clinicians to provide input and advice with a higher degree of certainty to our patients,” he adds.

Lack of access to approved therapies

The prevalence of obesity among adults in the U.S. has continued to increase in recent years, from 33.7% in 2007–2008 to 39.6% in 2015–2016.

The condition also has associations with an increased risk of diabetes, heart disease, cancer, and premature death.

People often struggle to lose weight; due to either a lack of effectiveness of Food and Drug Administration (FDA)-approved treatments or no access to healthcare professionals who can provide anti-obesity therapy.

The researchers write that many people turn to nonprescription weight loss supplements in the belief that they are “natural” or “clinically proven.” Consumers may even believe these products are as safe as FDA-approved drugs.

In addition, the scientists say that healthcare professionals have incomplete information about the scientific claims made by the promoters of such therapies.

Products and therapies reviewed

The researchers reviewed randomized controlled trials that evaluated the efficacy of 14 dietary supplements, therapies, or both, including:

• acupuncture
• green tea
• ephedra or caffeine
• guar gum
• chitosan
• calcium-vitamin D supplements
• chocolate or cocoa
• chromium
• pyruvate
• mind-body therapies

Out of a total of 315 trials, they judged 52 to have a low risk of bias — due to flaws in their design or reporting of results, for example — and sufficient data to support any claims of efficacy.

Of these, 16 reported statistically significant weight reduction throughout the trial, ranging from 0.3 to 4.93 kilograms.

However, the authors write that these reductions were not “clinically significant.”

“An outcome can be statistically significant without being clinically significant,” Prof. Batsis told Medical News Today.

He said clinical guidelines consider a weight loss of more than 5% to be clinically significant.

“During our review of supplement studies, in the rare cases where people did lose weight, they did not drop enough pounds to make a positive impact on their health,” he said.

In their paper, the researchers conclude:

“Despite there being a number of studies evaluating dietary supplements and alternative therapies for weight loss, this review does not support strong, high-quality evidence of the efficacy of any of the products.”

Looser regulation

In 1994, the Dietary Supplement Health and Education Act loosened regulation of the dietary supplement industry.

Under the Act, the FDA does not regulate supplements in the same way as prescription anti-obesity medications. However, while manufacturers cannot claim their products can cure, treat, or prevent any disease, they do have to provide evidence of their safety.

The Office of Dietary Supplements publishes fact sheets about these products and maintains a database of their ingredients and labels.

In a strongly worded opinion piece that accompanies the paper, members of the Clinical Committee of the Obesity Society note that annual sales of weight loss supplements are worth $30 billion worldwide, despite “subpar evidence.”

The authors call on regulatory authorities “to critically examine the dietary supplement industry, including their role in promoting misleading claims and marketing products that have the potential to harm patients.”

‘Hodgepodge’ of products and therapies

Steve Mister, president and CEO of the Council for Responsible Nutrition (CRN), which represents the supplement industry, challenged the study’s validity. CRN is “is the leading trade association representing dietary supplement and functional food manufacturers and ingredient suppliers.”

In a statement provided to MNT, he questioned the inclusion of acupuncture, mind-body interventions, and chocolate, among others, in what he described as a “hodgepodge” of products and therapies.

He added that manufacturers do not market vitamin D and calcium for weight loss.

“There are many safe, beneficial weight management dietary supplements on the market with research support in this category, along with supplements that help fill nutrient gaps for consumers who do not get all the nutrients they need from food alone, especially when they are limiting calories or engaging in strenuous exercise,” he said.

“The recent review only covers a handful of ingredients in this area and should not diminish the supportive role these products play for consumers’ weight management programs,” he added.

However, he agreed with the scientists’ call for more research, adding that industry and academia should strengthen their research collaborations.

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