Taking Weight Loss Supplements? They Probably Won't Work, Study Suggests

There is little high-quality evidence that dietary supplements and alternative therapies marketed for weight loss actually work, a study has concluded.

Researchers looked at 315 existing studies of supplements and alternative therapies. These were randomized controlled trials, in which participants were monitored after being randomly assigned an intervention.

The 315 trials looked at the following products: calcium and vitamin D; chitosan, a type of sugar taken from crustacean shells; cocoa/chocolate; the metal chromium; ephedra, a plant often taken with caffeine; garcinia, a plant that has hydroxycitrate in the rind, which is thought to affect the appetite; green tea; guar gum, which comes from the seeds of the Cyamopsis tetragonolobus plant; conjugated linoleic acid, which is found in dairy and meat products; phaseolus, which is extracted from the white kidney bean; the compound phenylpropylamine; and pyruvate, which the body produces when it breaks down glucose.

The researchers—whose paper "A Systematic Review of Dietary Supplements and Alternative Therapies for Weight Loss" was published in the journal Obesity on June 23—also looked at studies on acupuncture and mind-body therapies.

Participants in 16 of the 315 trials reported a significant difference in their weight compared with the people given a placebo, ranging from 0.3 kilograms (0.66 pounds) to 4.93kg (10.8 pounds).

Melinda M. Manore, emeritus professor in nutrition and exercise at Oregon State University, who was not involved in the research, told Newsweek via email that the weight loss in the 16 studies was small, "especially compared to the amount of weight most overweight/obese people want to lose (20 to 60 pounds or more).

"In addition, weight loss supplements are expensive and many have side effects; thus, the risks of use do not outweigh the benefits."

It was difficult for the authors of the "Systemic Review" paper to evaluate the products and therapies because many of the studies were of poor quality, had small sample sizes, did not follow up with participants for long periods of time, and were funded by companies selling weight loss products, meaning they could be biased.

The studies that were featured also involved different participants and interventions, which made direct comparisons tricky, according to one of the authors, Dr. John Batsis, associate professor in the Division of Geriatric Medicine at the University of North Carolina School of Medicine.

He told Newsweek this was compounded by the fact many of the studies featured a combination of dietary supplements, doses or formulations.

The review paper comes as America struggles with an obesity epidemic. According to the U.S. Centers for Disease Control and Prevention, 42.2 percent of the adult population had the condition in 2017-18.

The CDC website states that "the key to achieving and maintaining a healthy weight isn't short-term dietary changes; it's about a lifestyle that includes healthy eating and regular physical activity."

The website does not mention dietary supplements or alternative therapies.

Manore said: "Weight loss isn't as 'simple' as taking a 'pill'." She pointed out that most studies on weight loss supplements required the person to make lifestyle changes, such as to their diet or levels of physical activity.

Batsis said: "This study provides health care professionals with evidence-based data on the quality and efficacy of weight loss supplements and alternative therapies. Despite their popularity, there is a lack of high-quality clinical trials evaluating weight loss outcomes, which underscores the need for well-designed and adequately powered studies to minimize bias and provide definitive clinical guidance."

He added: "Clinical providers should rely on evidence-base interventions to support weight-loss such as behavioral weight loss interventions, medications or bariatric surgery."

An article accompanying the paper, also published in the journal Obesity and co-authored by Batsis, pointed to a "lack of regulatory oversight and rigorous testing of [supplements'] efficacy and safety" in the U.S.

"A number of products and services claiming to promote weight loss are directly marketed to individuals with obesity and those wanting to lose weight. These products are not regulated as 'drugs' by the Federal Drug Administration but, rather, are treated as dietary supplements if ingredients are 'generally regarded as safe,' requiring little or no testing to show efficacy or safety," the article's authors wrote.

They added: "Regulatory authorities should protect consumers by ensuring accurate and safe marketing claims and preventing promotion of unproven and potentially unsafe products and claims."

Newsweek has contacted the FDA for comment.

The take-home message, according to Manore, is: "Don't believe the advertisements, weight loss supplements do not provide quick weight loss nor do they help with long-term weight maintenance."

What the researchers found in the 315 studies

Acupuncture: No high-quality studies recorded a significant difference in weight.

Calcium-vitamin D supplementation: Of the five studies cited that did not have high levels of potential bias, none found significant differences in weight in the participants.

Chitosan: One article with a low risk of bias reported a change in weight of 2.3kg (5 pounds) over 6 weeks.

Cocoa/chocolate: The one study with a low risk of bias did not find any significant changes.

Chromium: Three studies had low levels of bias, with one showing weight loss.

Ephedra or caffeine: Ten studies had a low risk of bias, with five reporting statistically significant weight loss between 0.3kg (0.6 pounds) and 4.9kg (10.8 pounds).

Garcinia and/or hydroxycitrate: Two studies with a low risk of bias showed weight loss ranging from 1.3kg (2.8 pounds) to 3.6kg (7.9 pounds).

Green tea: Two studies with a low risk of bias found weight loss ranging from 1.5kg (3.3 pounds) to 1.7kg (3.7 pounds), for less than eight weeks.

Guar gum: No high-quality studies.

Conjugated linoleic acid: One of the high-quality studies showed weight loss of between 1.5kg (3.3 pounds) and 3kg (6.6 pounds).

Mind-body: Behavioral therapies such as mindfulness and stress management were tested, as well as hypnosis, meditation and massage. No significant differences in weight were found in the high-quality studies.

Phaseolus: No studies had a low risk of bias.

Phenylpropylamine: One high-quality study did not find significant changes in weight.

Pyruvate: No high-quality studies.

weight scales, getty, stock
A stock image shows a person weighing themselves. Supplements that promise to help people lose weight are unlikely to work, according to researchers. Getty Images