The placebo-controlled study published this month in Obesity Pillars found participants taking Calocurb alongside lifestyle advice experienced greater reductions in body weight, body fat and visceral fat than those receiving a placebo.
Importantly, researchers found no indication of skeletal muscle loss in either group during the six-month intervention.
The authors concluded that “appetite suppressing nutraceuticals may be a useful adjunct therapy for individuals receiving lifestyle change advice for the purpose of weight loss.”
The study was funded by Calocurb Ltd. Several authors reported affiliations with Calocurb Ltd., while others declared no competing interests. The study evaluated Calocurb, containing the proprietary bitter hop extract Amarasate.
Moving beyond appetite
While earlier studies showed Calocurb reduced hunger and calorie intake, this is the first to demonstrate that those effects translate into measurable improvements in body composition over the longer term.
“What those studies couldn’t tell us was whether those appetite effects would add up to something meaningful over a longer period in the context of real weight loss and body composition,” Dr. Edward Walker, senior scientist at the New Zealand Institute for Bioeconomy Science, told NutraIngredients.
“This latest trial answers that question directly, showing that the same mechanism translates into measurable, sustained fat loss and body composition improvement over 24 weeks,” he added.
The 150 adult participants in New Zealand were aged 18 to 45 years with a body mass index (BMI) of 25-35 kg/m² and were randomly assigned to receive either Calocurb or a placebo for 24 weeks while both groups attended identical monthly dietitian-led sessions covering healthy eating and physical activity. Compared with placebo, the Calocurb group lost 4.3% of body weight (3.8 kg) and 4.5 kg of fat mass, while the placebo group lost 0.5% of body weight (0.4 kg) and 0.7 kg of fat mass. The Calocurb group also experienced greater reductions in visceral fat, with no indication of overall muscle loss based on bioelectrical impedance analysis (BIA).
The researchers also reported that “weight loss was achieved with no indication of overall loss of muscle mass as per bioelectrical impedance analysis.”
Dr. Walker said evaluating the finished product rather than relying on evidence for individual ingredients strengthens the clinical relevance of the findings.
“Supplements often use multiple sources of clinical data corresponding to the ingredients making up the product...this study uses the actual ingredients in the finished product, connecting the earlier mechanistic work to a long-term, clinically meaningful outcome in body composition,” he said.
Growing focus on muscle preservation
Maintaining muscle during weight loss has become an increasing focus for both healthcare professionals and consumers, particularly as the use of prescription GLP-1 medicines continues to grow.
Dr. Walker stressed that Calocurb is not intended to compete with those medicines. “It’s better understood as an option for people who can’t access, can’t tolerate, or don’t want to go on prescription GLP-1 therapy,” he said.
He added that future research could investigate whether the ingredient could play a complementary role alongside pharmaceutical weight-loss treatments.
Real-world study
Dr. Walker described the trial as reflecting a real-world weight management program because participants received only modest lifestyle support beyond monthly educational sessions.
“This was a ‘real-world’ study where the participants were given minimal dietary and lifestyle advice.”
Of the 150 participants enrolled, 128 completed the study. Around 10% of participants taking Calocurb required temporary dose adjustments because of mild gastrointestinal side effects, mainly nausea and diarrhea during the dose-escalation phase.
The researchers acknowledged several limitations, including that most participants were women and that older adults and people with diagnosed metabolic disease were excluded.
Dr. Walker said the company is continuing a five-year clinical research program investigating the ingredient in additional populations and product formats.
The authors concluded that further research is warranted, but said the findings support gastrointestinal bitter receptor activation as a promising non-pharmacological approach to improving body composition during weight loss.
Source: Obesity Pillars Volume 19, 2026, 100299, ISSN 2667-3681, https://doi.org/10.1016/j.obpill.2026.100299. “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.” Authors: Walker, E. et al.
