NZ weight-loss ‘supplement’ works?

In the media last week there was a lot of coverage for ‘Calocurb’, a weight-loss medication made in New Zealand from hops.  The most dramatic headline was probably from Newstalk ZB: Kiwi research into plant-based Ozempic alternative shows ‘groundbreaking’ results

Usually this sort of thing is either vibes-based or mostly imaginary. This time, though, there is an actual randomised placebo-controlled trial, registered in the ANZ trial registry, and a paper published in a reasonable journal, with key results

One hundred and twenty-eight participants completed the program. The [bitter hop extract] treatment group exhibited a greater reduction in weight (3.8%) and fat mass (3.9 kg) after 24 weeks when compared to placebo control (p < 0.05)

You might be worried that a mere p<0.05 is pretty marginal, but that seems to just be bad reporting in the paper, which actually shows better evidence than that.

So: this stuff has a non-zero average benefit that persists at least for a reasonable duration of treatment.  There are claims that the benefit is due to stimulating the famous GLP-1 peptide and that the treatment preserves muscle mass.  These seem a bit less clear — GLP-1 was up, but establishing mechanism of action is harder than that, and it’s possible muscle mass didn’t fall detectably just because the reduction in weight wasn’t huge.

The trial is important, because it’s enough to support advertising in the US as a ‘dietary supplement’ — which in the US means ‘largely unregulated drug’. The combination of the trial results and the fact that it’s a plant extract potentially opens up a big market. It’s also important because it’s unusual. Almost no-one outside the pharmaceutical sector does randomised trials with meaningful measurements!   Previous products supported by research at Plant and Food tended not to go further than showing the supplement has some detectable biological effect in people (what the pharmaceutical sector would call “Phase II”). This trial looks at a measurement (weight) of genuine interest to people taking a weight-loss drug (Phase III), and shows a modest but non-zero impact.

It’s worth comparing the trial with the FDA guidance for weight-loss drugs, though. If you want to market a drug for weight loss, the FDA’s (non-binding) advice is

In general, a drug is considered effective for weight reduction and maintenance in patients with obesity or overweight with comorbidities if, after 1 year of treatment at the maintenance dosage, the difference in mean percentage weight reduction between the investigational drug and control treated groups is at least 5% and the difference is statistically significant. [emphasis added]

The hop extract trial is too short to satisfy the FDA as a drug, and the difference in weight is too small.  The distinction between drug and ‘dietary supplement’ is critical — this product is much less effective than the injected peptides, but it’s also much cheaper and less regulated.  There may be more competition from the new non-peptide GLP-1 agonist pills that are just emerging, but there’s still a good chance that lots of people in the US who have finished a course of Ozempic or can’t afford one will decide they don’t have enough hops in their usual diet and need supplementing.