FORMI Weight Loss Complex, reviewed against the SlimBiome trial

Holland and Barrett has a new own-label brand, FORMI, and the weight-management product just launched under it is a raspberry powdered drink sachet. The retailer did not announce it, as far as we could find. The ingredient supplier did: OptiBiotix Health plc, whose SlimBiome complex sits inside the sachet, published the launch as a regulatory announcement on 2 September 2026, under a three-year non-exclusive trademark licence it says was signed in December 2025.

One limit before the arithmetic. This is a reading of that announcement and of the published trial behind the ingredient, not of a pack: we went looking for a FORMI listing on 3 September 2026 and could not open one that returned any product detail to us. Where a pack and a press release disagree, the pack governs.

What the announcement actually publishes

Those last two rows are the review: a launch announcement is not a label, but it is what the buyer has today.

The arithmetic the pack has to satisfy

The Roehampton crossover trial, published open access in the European Journal of Nutrition in 2025, administered 3 g of the complex. Usefully, the paper states the composition outright: glucomannan 33.33%, fructo-oligosaccharides 66.67%, chromium 0.003%.

Run that through and the studied 3 g dose contained about a gram of glucomannan alongside about two grams of FOS. The same paper notes earlier longer-term work dosing 3 g three times a day.

So the number a buyer needs is simple. For a FORMI sachet to deliver the fibre the trial describes, it has to carry 3 g of the complex — a gram of glucomannan — and the longer-term work dosed that three times daily. Anyone who has read our earlier piece on what the glucomannan claim requires will recognise both the amount and the regimen. Whether it is printed on the sachet is the whole question.

OptiBiotix’s chief executive is quoted calling SlimBiome “supported by clinical studies, authorised health claims in major territories and multiple international awards”. That is the company’s wording and it stays the company’s. We have not seen the pack, and we have not read the relevant claims register, so we make no finding in either direction about what claim this product may carry.

What the trial found, and what it did not

Sixteen healthy-weight adults, eight men and eight women, averaging about 26 years old, took 50 g of dextrose with or without 3 g of the complex and were followed for 150 minutes.

Insulin came out lower with the complex at 45, 75 and 90 minutes, and the area under the curve was reduced at p=0.034. At 150 minutes the paper reports 37.2% less hunger, 55.4% greater fullness and a 32.4% lower desire to eat, each measured on a visual-analogue scale, with fullness and desire to eat both at p=0.002.

Blood glucose showed no significant difference at any timepoint, area under the curve p=0.731. The announcement lists the on-pack claims as supporting weight management, helping to control blood sugar, and supporting satiety. The middle one is not what this trial produced.

Body weight was never measured at all. The study ran two and a half hours in people who were not overweight, its authors call it acute, it was funded by OptiBiotix under a research agreement with Roehampton, and two of its nine authors are affiliated to the company.

The chromium line

The paper’s discussion states that the chromium content of the single dose it tested was 15 µg, and names 250 µg a day as the maximum intake suggested by the WHO and EFSA. Three such doses would be 45 µg, comfortably inside that ceiling. The same discussion is candid that chromium studies fail to show an effect in healthy people at intakes within that limit, so the chromium is unlikely to be what carried the result.

No chromium figure appears in the announcement. If you already take chromium, do that sum before the first sachet, and ask a pharmacist.

Pros and cons

Verdict

Our advice is narrower than the marketing. If the fibre is what you are buying, buy on the fibre figure: find the complex dose per sachet and check it reads 3 g. If the pack does not say, that silence is your answer.

This is a British retail product, so the standing note at the foot of this site names the wrong regulator: to our knowledge no United States agency has evaluated it. Nothing here diagnoses, treats, cures or prevents anything, and none of it is medical advice. Bulking fibres expand on contact with water, which makes the water instruction on any glucomannan product a safety instruction rather than a suggestion, and makes a swallowing difficulty or a history of obstruction a reason to ask a clinician first.