Ranked by evidence within the category
Weight loss supplements: what the evidence says
This category covers 45 supplements for weight loss and appetite: 1 is rated strong, 9 moderate and 35 limited. The only strong entry is meal replacement shakes, which beat conventional calorie-restricted diets through portion control rather than any special ingredient. Moderate items such as L-carnitine, MCT oil, capsaicin and carb blocker formulas produce real but small losses of a kilogram or two at best, while classic fat burners, including garcinia cambogia, raspberry ketones, green coffee bean extract and glucomannan, are rated limited.
Evidence last reviewed: September 2026
Strong evidence (1)
This is one of the few weight-management categories with genuinely good evidence: structured meal replacement produces more weight loss than conventional calorie-restricted diets in randomised trials.
Moderate evidence (9)
L-carnitine produces a small but real amount of extra weight loss (around 1 kg) and modestly improves glycemic markers in type 2 diabetes, but it is not the fat-burner marketing implies and does little for exercise performance in people who eat meat.
Replacing long-chain fats with MCTs produces a small but real reduction in body weight and fat mass, on the order of half a kilogram over a few weeks.
The pungent compound in chilli peppers, which measurably raises energy expenditure and slightly lowers food intake.
The common kitchen spice, concentrated.
Membrane fragments from spinach leaves that slow fat digestion and prolong satiety signalling.
A highly viscous soluble fibre from the guar bean.
White kidney bean extracts that inhibit the starch-digesting enzyme alpha-amylase.
A rare sugar that tastes close to sucrose but is barely metabolised, so it contributes almost no calories.
A sugar alcohol that is almost entirely absorbed and excreted unchanged, so it adds virtually no calories and does not raise blood glucose.
Limited evidence (35)
CLA reduces fat mass by roughly 0.
White kidney bean extract really does inhibit starch-digesting amylase, but the weight effect in humans is small and the trial base is weak: an early meta-analysis found no significant weight difference versus placebo, and a more recent one found about 1.
Glucomannan is an extremely viscous soluble fibre with decent evidence for lowering LDL cholesterol, but the weight-loss case has weakened badly: the best meta-analysis found no significant weight difference versus placebo.
Chitosan is sold as a "fat magnet", but the Cochrane review found no clear difference in faecal fat excretion — the exact measure the mechanism predicts.
Green coffee extract became a bestseller on the back of a trial that was later retracted and a marketing campaign that drew regulatory enforcement.
The best-designed trial of Garcinia cambogia — a 135-person randomised study published in JAMA — found no weight or fat loss beyond placebo.
There is no published randomised trial of raspberry ketone as a single ingredient in humans — none.
Almost all human data on Cissus come from a small cluster of trials testing proprietary multi-ingredient products, so the eye-catching weight-loss numbers cannot be credited to Cissus itself.
Forskolin's fat-burner reputation rests on two small 12-week trials from 2005 - and neither actually produced weight loss.
Across systematic reviews, no over-the-counter fat burner ingredient produces clinically meaningful weight loss, and the category's history is a repeating cycle of an ingredient becoming popular, then being withdrawn after serious harms.
7-Keto DHEA (3-acetyl-7-oxo-DHEA) is marketed as a non-hormonal DHEA metabolite that raises metabolic rate, but a systematic review of its weight effects found the evidence thin, industry-linked and unconvincing.
Bitter orange (Citrus aurantium) and its alkaloid p-synephrine became the post-ephedra fat burner ingredient, but a systematic review and meta-analysis found essentially no meaningful weight-loss effect while confirming measurable cardiovascular activity.
Hoodia was the appetite suppressant of the 2000s, backed by a compelling San Bushmen story and almost no clinical data.
Ashitaba is a Japanese herb whose yellow sap chalcones (4-hydroxyderricin, xanthoangelol) have one small positive RCT for visceral fat.
Yacon syrup is essentially a fructooligosaccharide syrup — a prebiotic fibre with real effects on satiety and bowel habit.
Green tea extract is the single most common ingredient in "fat burner" formulas, and the Cochrane review found it produces essentially no weight loss — a pooled difference of 0.
Marketed hard as a "belly fat probiotic" on the strength of two Japanese fermented-milk trials of strain SBT2055.
A brown-seaweed carotenoid that increases thermogenesis in rodents.
A 1990s fat-loss ingredient still sold today.
A yohimbine isomer sold in fat burners for 'stubborn' fat.
A plant alkaloid with beta-2 adrenergic activity, used in fat burners and pre-workouts.
A phenylethylamine alkaloid from barley sprouts, added to fat burners on the theory that it prolongs stimulant effects.
Seed extract of Irvingia gabonensis, marketed on the back of trials reporting dramatic weight loss.
An Indian edible cactus traditionally used to blunt hunger during long journeys.
A Brazilian herb (Cordia ecalyculata) sold for appetite suppression and water weight.
A West African spice (Aframomum melegueta) that activates brown fat and modestly raises energy expenditure in small human studies.
A fat-derived signalling molecule the gut makes after a meal, sold as an appetite suppressant.
A common garden weed with a long folk reputation as a slimming and diuretic herb.
Fiber-and-herb blends marketed as natural alternatives to GLP-1 drugs.
Blends of dandelion, uva ursi, juniper and similar herbs sold to shed water weight.
Slimming teas built around senna and other stimulant laxatives, sold as detoxification.
Oral blends of circulation herbs such as gotu kola, horse chestnut and butcher's broom, sold to smooth skin dimpling.
The leaf of Nelumbo nucifera, used in Chinese medicine and sold as a slimming tea for its quercetin glycosides.
Semi-fermented tea whose catechins and caffeine raise fat oxidation slightly in small metabolic studies.
Microbially fermented tea popular in China for weight and cholesterol.
Comparison guides for this category
Psyllium, glucomannan, inulin, oat beta-glucan or acacia?
L-carnitine, acetyl-L-carnitine, L-carnitine L-tartrate or propionyl-L-carnitine?
Green tea extract, matcha, white, oolong, pu-erh or black tea theaflavins?
Plain MCT oil or pure C8?
The adrenal prohormone or the metabolite sold for fat loss?
Partially hydrolysed guar gum or plain guar gum?
Yohimbine hydrochloride, whole yohimbe bark or rauwolscine?
Goals these supplements are ranked for
An evidence-ranked guide to weight-loss supplements: the one approach with strong evidence, the few that add a little, and the fat burners…
Our verdict
If a supplement is going to help, it is a structured meal-replacement plan used in place of meals, not added on top of them. Be sceptical of fat burner and GLP-1 support formulas, and of any promise of fast loss: even the better moderate options move the scale only slightly.