Could Bitter Hop Extract Be a New Natural Option for Weight Loss?
At first glance, this article may seem far removed from an oncology website—a study of a weight-loss supplement. However, obesity is now an established risk factor for 13 different types of cancer , and in the era of GLP-1 injections, “losing weight without losing muscle” has become an increasingly discussed topic. In this article, we will compare a supplement made from bitter hop extract both through its own data and contextually with today's popular weight-loss drugs—and address a financial conflict of interest in this study that cannot be ignored with the same clarity.
In this 24-week study, the group receiving bitter hop extract (BHE= bitter hop extract) lost significantly more weight and fat mass than the placebo group, without losing muscle mass. What kind of finding is this, really?
The International Agency for Research on Cancer (IARC) recognizes that excess body fat is associated with at least 13 types of cancer—breast (after menopause), uterine (endometrial), colorectal, kidney, liver, pancreatic, esophageal, stomach, gallbladder, ovarian and thyroid cancers, and multiple myeloma are among them. Therefore, weight management is directly relevant to oncology—both for primary prevention and for reducing the risk of a second cancer .
New Zealand was the setting for this randomized, double-blind study, which enrolled 150 healthy adults aged 18-45 with a BMI of 25-35 (128 completed it). Both groups received 1 hour of group diet/exercise counseling each month; additionally, one group received 500 mg daily of bitter hop extract (BHE) called Amarasate®, while the other received a matched placebo—the capsules were divided to be taken before two main meals.
The statement “no muscle loss” in the Medscape summary is correct but may be read without full context. The study's own statistical analysis finds no significant treatment effect between BHE and placebo on the change in muscle mass —in other words, neither group lost muscle (probably thanks to monthly lifestyle counseling); this is not a proven “muscle-preserving” effect specific to BHE. What should actually be compared is BHE not causing muscle loss relative to GLP-1 drugs (discussed below), rather than relative to placebo.
The idea behind Amarasate is a mechanism called the “Bitter Brake”: intensely bitter compounds are delivered directly to the small intestine without being broken down in the stomach (hence the use of delayed-release capsules), stimulating enteroendocrine cells there and increasing the release of the body's own cholecystokinin (CCK), GLP-1 and PYY hormones.
GLP-1 agonists such as semaglutide and tirzepatide involve injecting a long-acting, synthetic GLP-1-like molecule from outside the body. BHE instead attempts to stimulate the body's own GLP-1/CCK/PYY production—a “milder,” but probably less potent approach. This distinction may also partly explain the difference in effect size below.
The study's own discussion places BHE's effect in the context of historical drug and supplement data. We have put this into a table—with an important warning: these are different studies, populations and periods, and cannot be directly compared:
| Intervention | Reported weight loss | Note |
|---|---|---|
| Probiotic / prebiotic | <1 kg | Meta-analysis data |
| Berberine | ~2,1 kg | Meta-analysis data |
| BHE (this study) | ~3,8 kg (4,3%) | 24 weeks, RCT |
| Orlistat | ~%3 | Older-generation drug |
| Sibutramine / rimonabant | ~%5 | Withdrawn from the market because of safety issues |
| Liraglutide (Saxenda) | ~%5 | GLP-1 agonist, injection |
| Semaglutide (Ozempic/Wegovy) | ~%10+ | GLP-1 agonist, injection |
| Tirzepatide (Mounjaro) | Above 10% | Dual GIP/GLP-1 agonist |
As the study also emphasizes, a significant portion of the substantial weight loss achieved with GLP-1 agonists can be loss of muscle mass , and when treatment is stopped, weight is generally rapidly regained. BHE's claimed advantage is having less of these two problems (muscle loss and rapid regain) alongside a more modest effect—but this comparison was not directly tested in this study and is the authors' own interpretation.
When assessing the strength of this study's evidence, the following information is of central importance:
- The study was funded by the company selling the product, Calocurb Ltd .
- The other funder and the institution conducting the research, New Zealand Institute for Bioeconomy Science (a government-affiliated research organization), licensed this bitter hop extract to Calocurb itself and owns a small stake in the company.
- In other words, the institution testing the product also owns its intellectual property and is a partial shareholder in the company selling it—a classic issue of “who benefits financially from the result.”
- Moreover, this study continues earlier studies published by the same research group (Walker and colleagues) in 2019, 2022 and 2024—meaning there is not yet a finding replicated by an independent group.
This does not mean the study's data are wrong—the methodology (randomization, double blinding and ethics approval) appears appropriate. However, accounting for this financial connection when interpreting the results is necessary for responsible reading.
- “Natural supplement emerges as a rival to weight-loss injections!”
- “A solution for losing weight without muscle loss has been found”
- “Science-backed, safe weight-loss supplement”
- The effect size (4,3%) is far below that of modern GLP-1 drugs (10%+); it is closer to older-generation weight-loss drugs
- “Muscle preservation” is not a proven effect specific to BHE—there is no significant difference from placebo
- The institution funding and conducting the study has a direct financial interest in the product
- It was tested only in healthy people aged 18-45 without comorbidities—it cannot be generalized to a broader population
- It has not yet been confirmed by an independent research group
- Body composition was measured using bioelectrical impedance analysis (BIA) rather than the gold-standard DEXA/MRI—a less precise method.
- Energy intake was determined through self-reported 4-day food diaries—a method prone to systematic underreporting.
- 75% of participants were women, and the age range was limited to 18-45—there may be issues with sex and age representation.
- This study does not answer “what happens when treatment stops” after 24 weeks (a known issue with GLP-1 drugs).
- No information was found indicating that the Amarasate/Calocurb product is officially sold in Türkiye —at the time this article was written, the product was most likely not on the Turkish market.
- Food supplements in Türkiye are subject to a very different regulatory framework from medicines —supplements do not have to prove efficacy and rely only on safety/content declarations. This does not mean every product claiming “there is a scientific study” has the same strength of evidence.
- In Türkiye, GLP-1 drugs (semaglutide and tirzepatide) are prescription medicines and, depending on SGK conditions, are accessible under certain conditions; A similar situation applies to Mounjaro —these drugs are much more powerful and have much stronger evidence than this supplement, but are more costly and require a prescription.
- An extra warning for cancer patients/survivors: This study did not test people with any history of cancer. Although weight management matters for reducing cancer risk, patients receiving active treatment or at risk of sarcopenia should consult their oncology team before starting any supplement.
If you are considering this kind of supplement, realistic expectations matter: the effect in this study is substantially smaller than that of modern GLP-1 drugs. “Natural” and “there is a scientific study” do not automatically mean “highly effective” or “proven impartially”—studies conducted by an institution with a direct financial connection to the manufacturer, as here, should be read carefully.
Questions you can ask: “Could this supplement interact with my other medicines (including cancer treatment, if any)?”, “How applicable are this study's results to my situation (age and comorbidities)?”, “Is there a more suitable option for weight management with stronger evidence for me?”
Obesity is an established cancer risk factor, and in the era of GLP-1 drugs, “losing weight without losing muscle” is becoming an increasingly important clinical question. This study shows the answer a non-drug option proposes—but also illustrates why evidence literacy matters so much in supplement research.
In a 24-week randomized, double-blind study, the group receiving 500 mg BHE daily lost 4,3% of body weight, 4,5 kg of fat mass and 33 cm² of visceral fat compared with placebo (all p<0,05); hunger and the desire to eat decreased markedly. Muscle mass did not decline in either group, but a “muscle-preserving” effect specific to BHE was not demonstrated statistically.
The institution funding and conducting the study has a direct financial interest in the product (license + shares)—a serious conflict of interest. There is no independent replication; it extends previous studies by the same research group. Body composition was measured by BIA (not DEXA/MRI), and dietary data were self-reported. It was tested only in healthy participants without comorbidities and within a limited age range. What happens after treatment stops is unknown.
This is not an option to replace GLP-1 drugs; at best, it could be modest lifestyle support for individuals who do not want to or cannot use medication. Any supplement decision for cancer patients and survivors should be assessed with the oncology team, taking current treatment and nutritional status into account.
Can an independent group without a financial conflict of interest replicate these findings? Is weight regained when treatment stops, or is the effect more durable than with GLP-1 drugs? What would safety and efficacy be in special populations such as cancer patients/survivors? And a broader question: should products in the “natural/supplement” category be required to meet an evidence standard closer to that for medicines?
- Walker E, Lo K, Smirk I, et al. Bitter Hop Nutraceutical Stimulates Fat Mass Loss While Preserving Muscle Mass in a Cohort of Individuals With Overweight or Obesity Receiving Diet and Exercise Advice. Obes Pillars. 2026;19:100299.
- National Cancer Institute. Obesity and Cancer Fact Sheet.
- Lauby-Secretan B, et al. Body Fatness and Cancer — Viewpoint of the IARC Working Group. N Engl J Med. 2016;375:794-798.
Editor's note: This content is a Turkish adaptation of an open-access clinical study published in Obesity Pillars; it is for general information and is not medical advice. This study was funded by the company selling the tested product and an institution connected to the product through licensing/shareholding—this is an important financial conflict of interest, and the results should be assessed with that information in mind. Food supplements are not subject to the same regulatory/efficacy evidence standards as medicines. This supplement has not been approved as a “treatment” in any country. Decisions about weight management, cancer risk and any supplement/medicine use should be made with the person's physician, considering their health and current treatments. Consult your physician for every decision regarding your health.
Was this article helpful?
Your feedback helps us improve our content.
