Health Reference LibraryWhich supplements for weight loss have evidence?
This entry is part of the Nutri Tailor Health Reference Library — cited research on supplements, nutrients and adjacent areas of health.
Summary
One substance holds an authorised GB weight-loss claim, glucomannan, konjac fibre, and only conditionally, "in the context of an energy restricted diet contributes to weight loss", at 1 g three times daily with one to two glasses of water before meals, choking warning included. After it comes protein powder, the practical tool that makes a deficit hold, then fibre. Green tea is small and not clinically important per Cochrane, chromium moved about 1 kg over 8 to 24 weeks, berberine meta-analyses disagree, the headline apple cider vinegar trial was retracted, and fat-burner blends are underdosed marketing. No capsule outruns the deficit.
How it works
Glucomannan absorbs many times its weight in water and forms a gel that fills the stomach and slows eating, which is an appetite mechanism rather than a fat-burning one, and it is the reason the authorised claim requires taking it before meals with water inside an energy-restricted diet, because it helps a person eat less and burns nothing. Protein works the same way, through satiety and the energy cost of digesting it, plus muscle protection. Caffeine and green tea catechins raise energy expenditure by a few percent, which sounds useful and compounds to almost nothing against a meal. Chromium may act on insulin signalling with a small effect in some trials. Nothing sold over the counter meaningfully increases fat oxidation in a way that shows up on the scales without a deficit, which is why every authorised and semi-credible option above is an adherence tool.
Timing
Glucomannan works from the first meals it precedes; judge alongside the deficit at four weeks. Protein satiety is immediate; the muscle effect builds over months with training. Chromium trials ran 8 to 24 weeks for their single kilogram. Weigh weekly, judge monthly.
Safety profile
Glucomannan carries a choking risk taken dry or with too little water and is avoided entirely with swallowing difficulties; it can also blunt absorption of prescriptions taken at the same time, so a gap applies. Berberine interacts with many prescriptions. Green tea extracts at high dose carry rare liver injury reports. Fat burners with undisclosed stimulants are the most adulterated supplement category. Anyone with a history of disordered eating should not be in this aisle at all, and the GP route on the sustainable weight loss page applies. Nutri365 checks for interactions and contraindications before suggesting any of these.
Special populations
People with type 2 diabetes on glucose-lowering prescriptions need the GP before glucomannan or berberine, because both can amplify effects. PCOS is the one context where inositol has its own evidence. Pregnancy is not a weight-loss context. Over-65s losing weight should bias to protein and training, not appetite suppressants.
Guideline positions
The GB nutrition and health claims register carries one authorised weight-loss claim, for glucomannan, with conditions: at least 1 g per quantified portion; consumer information that the effect is obtained with 3 g daily in three 1 g doses with one to two glasses of water before meals in the context of an energy-restricted diet; and a choking warning for people with swallowing difficulties, with advice to take with plenty of water. No claim is authorised for green tea extract, chromium for weight, berberine, apple cider vinegar or any blend, and EFSA has rejected weight-loss submissions for other substances for insufficient evidence. The trial-by-trial read of the common blend ingredients, with the Cochrane findings and the 2025 apple cider vinegar retraction, is on the [weight management blends page](/apps/learn/do-weight-management-supplement-blends-actually-work). The NHS rate and method sit on the [sustainable weight loss page](/apps/learn/how-to-lose-weight-sustainably-what-the-evidence-supports).
Practical framework
The method comes first, because every item here is an accessory to it, meaning the deficit, protein, fibre, training and sleep on [how to lose weight sustainably](/apps/learn/how-to-lose-weight-sustainably-what-the-evidence-supports). The shopping list is short. Protein powder applies where breakfast or lunch keeps missing the 25 to 30 g mark, whey or pea, compared on the [protein comparison](/apps/learn/whey-vs-pea-vs-collagen-which-protein-powder-should-you-buy). Glucomannan applies where appetite before meals is the failure point, taken exactly per the authorised conditions, 1 g with one to two glasses of water before each main meal, never dry and never with swallowing difficulties, and Nutri Tailor does not currently sell it, which does not change the ranking. Fibre comes from food first, with psyllium where the 30 g will not come from the plate. Chromium or inositol applies only where insulin resistance or PCOS is the actual context, per [supplements for blood sugar](/apps/learn/supplements-for-blood-sugar-what-the-evidence-supports) and the [inositol page](/apps/learn/inositol-what-it-does-who-it-helps-and-how-to-take-it). Fat burners, ACV gummies and detox teas are skipped entirely. Nutri365 reads whether the weight is moving because of the protein, the drinks that went, or the sleep, and whether a supplement is earning its place, checks for interactions and contraindications, and refers questions outside scope to a health specialist.
Common misconceptions
Fat burners do not burn fat. Apple cider vinegar's headline trial is retracted. A supplement stack cannot replace a deficit. Glucomannan's authorised claim only exists inside an energy-restricted diet, which is the part the adverts skip. Protein powder is the one purchase in this category most people genuinely benefit from.
Sources
- 2012. Commission Regulation (EU) No 432/2012, authorised health claims list, glucomannan entries (retained in the GB NHC register). European Commission / GB register.
- 2025. Lose weight (Better Health). NHS.
- 2026. Do weight management supplement blends actually work? (HRL entry with verified Cochrane and meta-analysis sources). Nutri Tailor HRL.