Fat Burners

Do fat burners work?

There's little good evidence that they do. The US National Institutes of Health says there's little scientific evidence that weight-loss supplements work, and where individual ingredients such as caffeine or green tea show any effect in studies, it's small. The NHS approach to losing weight is to aim to lose 0.5 to 1kg (1 to 2lbs) a week through what you eat and by being active for 150 minutes a week.

"Fat burner" is a product category name, not a description of what a product does. People searching for fat burners usually mean caffeine-based capsules, shots or sachets marketed for dieting. We sell them, but we don't claim any of them causes weight loss. For the wider picture, see weight management.

What is in a fat burner?

Most fat burners are built around caffeine, often with other ingredients such as green tea extract, L-carnitine, chromium or chitosan. The product names in this collection include caffeine-based thermogenic formulas, liquid shots and sachets, an L-carnitine and chromium product and a chitosan and chromium product.

"Adding more ingredients doesn't automatically make a product more effective. Each ingredient needs a clear purpose, an appropriate dose and evidence supporting its intended use," says Andy Arshad, who runs SupplementHQ. Look for a label that lists the amount of every ingredient, not a "proprietary blend" with one total. Our guide to reading a supplement label shows you what to look for.

How much caffeine is in a fat burner?

It varies widely, so check the caffeine per serving on the label and add it to everything else you drink. The European Food Safety Authority (EFSA) says single doses of up to 200mg and up to 400mg a day from all sources are safe for healthy adults, excluding pregnant women.

Caffeine has no authorised health claims in Great Britain. Products without caffeine are listed under stimulant-free products.

Are fat burners safe?

Products sold legally in the UK as food supplements must meet food law, but they can still cause side effects, mostly from caffeine. The International Society of Sports Nutrition lists faster heart rate, palpitations, anxiety, headaches and poorer sleep among commonly reported caffeine side effects, and says they increase with dose.

Green tea extract needs care too: EFSA found that 800mg a day or more of EGCG from supplements may be associated with initial signs of liver damage (EGCG is the main catechin, a type of plant compound, in green tea), while green tea drunk as tea is generally safe. Speak to your GP or pharmacist first if you're pregnant or breastfeeding, have a heart, liver or other medical condition, or take medication.

Are diet pills sold online safe?

Not always. The MHRA, the UK medicines regulator, warns that weight-loss products sold illegally may be fake, contaminated or incorrectly dosed and can cause heart problems, psychological effects and dangerously low blood sugar. It says not to buy prescription-only weight-loss medicines without a prescription.

An earlier MHRA warning puts it plainly: unlicensed slimming pills may contain dangerous ingredients, and the safest way to lose weight is to eat well and exercise. We sell food supplements only, not medicines.

Which weight-loss ingredients have authorised claims?

Only one food supplement ingredient has an authorised weight-loss claim in Great Britain: glucomannan (konjac fibre). The authorised wording is "Glucomannan in the context of an energy restricted diet contributes to weight loss", and it may only be used where a product provides 1g per portion, taken as 3g a day in three 1g doses with 1 to 2 glasses of water before meals, as part of an energy-restricted diet. None of the product names in this collection mention glucomannan.

Chromium and chitosan have authorised claims, but not for weight: chromium "contributes to normal macronutrient metabolism" where a product is at least a source of chromium, and chitosan "contributes to the maintenance of normal blood cholesterol levels" only at 3g a day.

How do you compare fat burners?

Compare the caffeine per full serving, whether every ingredient amount is disclosed, and the cost per full serving. Check how many servings the tub really gives at the dose the label recommends.

"A tub advertised as 40 servings might only provide 20 servings when using the manufacturer's recommended full-strength dose. That can make a product appear better value than it actually is," says Andy.

How to compare value (example figures, not real products): a £30 tub of 120 capsules, with a full serving of 2 capsules containing 200mg caffeine, gives 60 servings at 50p each. A £20 tub of 60 capsules, with a full serving of 3 capsules, gives 20 servings at £1 each, twice the cost per serving.

Which is the best fat burner?

We can't name a best fat burner, because no product here is shown to cause weight loss on its own. What you can compare is how much caffeine you're getting, whether the label is fully transparent and the cost per serving.

"Where evidence is limited or inconclusive, we should say so openly," says Andy. If your goal is weight loss, the NHS Weight Loss Plan and our weight management guide are better starting points than any supplement, and if you are comparing protein per calorie, see diet and lean protein.

We sell the products on this page. That's our commercial interest, and it's why we show the evidence alongside them. This page is general information for adults, not personalised medical advice. Food supplements should not replace a varied, balanced diet.

Written by Andy Arshad, SupplementHQ. Last reviewed 11 October 2026.