Calocurb side effects: what the 24-week trial counted

Calocurb side effects are gastrointestinal: diarrhea, softer or loose stools, nausea, bloating and occasional heartburn, concentrated in the first days and during the dose ramp. In the 24-week C4 trial, six of the hop-extract group cut their dose for diarrhea or nausea and one withdrew for diarrhea; the authors call that dose adjustment in “approximately 10%” of participants.

Where the numbers come from

The trial is the C4 study published on PMC in the Obesity Medicine Association’s journal: received 3 May 2026, accepted 8 July 2026, collection date September 2026. It was randomised, double-blind and placebo-controlled, ran 24 weeks, and enrolled 150 adults aged 18 to 45 with a BMI of 25 to 35. The paper states it was funded in part by Calocurb Ltd and in part by the New Zealand Institute for Bioeconomy Science, the renamed Plant and Food Research, where it was conducted. The protocol was approved by the New Zealand Health and Disability Ethics Committee and the trial registered with ANZCTR as ACTRN12625001011471. Registered and ethics-approved describe the trial, not the product.

This desk read the trial paper, the Calocurb help-centre side-effects article, the 2019 calocurb.co.nz blog post and the 2018 Spinoff column on 15 September 2026. The efficacy half is covered in Is Calocurb clinically proven? The C4 trial in numbers; this piece is about the tolerability section, which neither brand page read here quotes.

What Calocurb side effects looked like in the trial

The dose was 500 mg a day of Amarasate bitter hop extract in canola oil, in delayed-release DRcaps capsules, four capsules per day, reached by a three-week escalation of 125 mg a week. Participants took half the daily dose at least an hour before each of the two main meals.

Of 150 randomised, 128 completed. Of the 22 who did not, 12 were on placebo and 10 on the hop extract. Two withdrew because of side effects from the capsule, one per arm: diarrhea on the extract, malaise on placebo.

Five hop-extract participants and one placebo participant took only half the prescribed dose for most of the study because of tolerability. One more hop-extract participant took a quarter dose. Of those six reduced-dose extract participants, three reported diarrhea only, two diarrhea and nausea, one nausea only.

The text we read does not give each arm’s size, so we compute no percentage; the authors’ Highlights do: dose adjustment “in approximately 10% of participants” to manage GI side effects, and otherwise “only small, non-significant, and temporary” increases in subjective nausea and GI discomfort during the escalation period. The results section reports no significant changes in the extract group’s safety measures, with values inside reference ranges.

How the brand pages describe the same thing

The help-centre article lists bloating, mild stomach discomfort, softer stools or mild diarrhea, fullness, and less commonly loose stools or heartburn. It gives no frequency and cites no study. Its “certified GRAS” line is the brand’s wording; this desk read no FDA page on those ingredients this run and makes no claim about that status.

The 2019 blog post calls the laxative effect “a bit of a detox” and “a spring clean for your body”. A trial in which roughly one in ten participants changed their dose is not a spring clean; it is a tolerability finding. Neither brand page read this run states a frequency, a denominator or a trial citation for its side-effect claims; the calocurb.com US safety blog was not read, so we say nothing about it.

What the trial cannot tell you

It excluded anyone on weight-loss medication including GLP-1 receptor agonists, anyone with diagnosed gastrointestinal disease or previous gut surgery, diabetics, and anyone outside 18 to 45 with a BMI of 25 to 35. In those groups the figures above were not measured. It ran 24 weeks, so nothing here speaks to longer use, and the company part-funded it, which does not make the counts wrong but belongs beside them. The distance between abstract and bottle that “clinically studied” papers over applies to safety sections too, which is why we reviewed green tea extract with its safety literature attached.

Questions readers ask

What are the side effects of Calocurb?

The documented ones are digestive. The brand’s help centre lists bloating, mild stomach discomfort, softer stools or mild diarrhea, a feeling of fullness, and less commonly loose stools or heartburn. The 2019 New Zealand blog adds a hoppy-tasting burp and mild indigestion. The 24-week trial recorded diarrhea and nausea as the reasons participants cut their dose, and diarrhea as the reason one hop-extract participant withdrew.

Does Calocurb cause diarrhea?

It can, and the trial put a count on it. Of the six hop-extract participants who reduced their dose for tolerability, five reported diarrhea (three diarrhea only, two diarrhea with nausea), and the one hop-extract withdrawal for side effects was for diarrhea. The brand’s help centre calls diarrhea a common early effect, especially at high doses.

How long do Calocurb side effects last?

The brand’s 2019 blog says they typically subside within the first 24 to 48 hours. The trial does not say that. Its authors describe a small, non-significant and temporary rise in subjective nausea and GI discomfort during the dose escalation period, which in that protocol ran for three weeks, and six hop-extract participants stayed on a reduced dose for most of the 24 weeks.

Should you take Calocurb on an empty stomach?

Every current page this desk read says yes. The help centre says about an hour before meals on an empty stomach; the 2019 blog says empty stomach with water; the trial dosed at least one hour before the two main meals on a relatively empty stomach. The opposite advice, to avoid a completely empty stomach, appears only in a since-deleted 2018 FAQ quoted by The Spinoff.

The usual small print, meant

None of this is a promise about your gut or your weight. The trial reports what happened to 150 people who met its criteria over 24 weeks; the brand pages report what the brand chooses to say. These statements have not been evaluated by the Food and Drug Administration, and no supplement is a substitute for medical care. If symptoms persist or are severe, the help centre’s own advice is to stop and talk to a healthcare provider, the one line on those pages we would not edit.