Systematic Review of Dietary Supplements, Alternative Therapies for Weight Loss

woman holding her jeans open to show how big they are on her following successful use of slimming tablets
Investigators assess the efficacy of dietary supplements and alternative therapies for weight loss.

Findings from a systematic review published in Obesity revealed the lack of strong high-quality evidence supporting the use of dietary supplements or alternative therapies for weight loss. These results demonstrate the continuing need for high-quality, well-designed, double-blinded randomized controlled trials (RCTs) with low risk of bias that demonstrate clinical efficacy of these frequently used, commercially available weight loss products and treatments.

Researchers reviewed 315 RCTs and categorized 52 as high-quality studies by using the Cochrane Collaboration’s risk-of-bias tool that calculates low risk of bias accompanied by sufficient evidence of efficacy. Only 16 of these high-quality studies noted significant between-group differences in weight loss (range: 0.3-4.93 kg).

Such high-quality evidence is required to accurately inform health care providers before they advise the use of such products or therapies in clinical practice. Studies of longer duration also are needed to assess the efficacy of these products and therapies over time.

Due to lack of regulatory restrictions, these dietary supplements and alternative therapies are often labeled as “clinically proven” or “natural” without proof of efficacy. This may misinform consumers, giving them a false sense of safety and leading to a belief that these commercialized products are a cure-all for obesity. Meanwhile, US Food and Drug Administration (FDA)-approved drugs that treat obesity may be undermined by these low-cost, easily accessible commercial products.

The investigators performed a literature search using PubMed, Cochrane Library, Web of Science, CINAHL, and Embase (Ovid). They obtained 20,504 citations from the search, reviewed 1743 full-text articles, and selected 315 peer-reviewed RCTs evaluating the efficacy of 14 dietary supplements and alternative therapies for weight loss as well as 39 miscellaneous categories. They performed a qualitative synthesis of these RCTs to address clinical questions regarding the efficacy of these weight-loss products and treatments so that health care providers could counsel their patients according to evidence-based research.

The 14 dietary supplements and alternative therapies for weight loss included acupuncture, calcium and vitamin D, chitosan, chocolate/cocoa, chromium, ephedra or caffeine, garcinia and/or hydroxycitrate, green tea, guar gum, conjugated linoleic acid, mind-body therapy, phaseolus, phenylpropylamine, and pyruvate.

Of the 66 studies determined to have a low risk of bias, only 18 high-quality studies demonstrated statistically significant evidence of efficacy for weight loss. They are chitosan (1), chromium (1 of 3), ephedra or caffeine (5 of 10), garcinia and/or hydroxycitrate (2 of 4), green tea (2 of 16), conjugated linoleic acid (1 of 5), and the 39 miscellaneous categories (6 of 16).

Limitations of this systematic review included the heterogeneity of the studies in which participants were not necessarily representative of typical patients seeking weight loss. This heterogeneity also resulted in an inability to conduct a formal meta-analysis due to different dosages, formulations, and combinations with other supplements.

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 


Batsis JA, Apolzan JW, Bagley PJ, et al. A systematic review of dietary supplements and alternative therapies for weight loss. Obesity (Silver Spring). 2021;29(7):1102-1113. doi:10.1002/oby.23110