Do fat burners work?
Most fat burners are caffeine and a list. The caffeine does something, the list mostly does not, and the doses are usually far below what the research used. Here is how to read one.
Short answer: the caffeine works, the rest mostly does not. Almost every fat burner is a caffeine tablet wearing a long ingredient list. A few of the other ingredients have small real effects at doses these products rarely reach, and several have none at any dose. Read the label and the picture usually becomes obvious.
This is one of the easiest categories to check yourself, because the answer is almost always printed on the back of the tub.
What is actually in them
Open a typical fat burner and you will find caffeine, then some combination of green tea extract, L-carnitine, garcinia cambogia, raspberry ketones, cayenne or capsaicin, and sometimes yohimbine.
They are not all the same, and it is worth separating them.
The one that does something
Caffeine. It raises energy expenditure slightly and it makes training feel easier, which is the larger effect. Both are real and both are well studied.
The catch is the dose, and the price. A fat burner containing 200mg of caffeine per serving is a strong coffee. You are usually paying £25 to £35 for something you could get for a few pounds.
WHAT A TYPICAL FAT BURNER IS DOING
The ones with small effects at doses nobody uses
Green tea extract. The active compound is EGCG, and combined with caffeine it does raise energy expenditure a little in studies. The doses used are typically several hundred milligrams of EGCG. Plenty of products contain a fraction of that and still list it prominently.
Capsaicin, from chilli, is similar. A measurable effect in trials, a small one, and usually underdosed in products.
The ones with essentially nothing
L-carnitine is involved in moving fatty acids into cells, which sounds promising and is why it appears everywhere. Supplementing it in people who are not deficient does not meaningfully change body composition.
Garcinia cambogia and raspberry ketones both had a moment on television and neither has held up. Reviews of garcinia find effects that are tiny where they exist at all.
The one to actually be careful with
Yohimbine is pharmacologically active in a way the others are not. It also raises heart rate and blood pressure and causes anxiety in a lot of people, and it interacts with several medications. If a product contains it, that is a conversation to have with a doctor rather than a detail to skim past.
The proprietary blend problem
This category is one of the worst for it. A fat burner listing "Thermogenic Blend 1,850mg" with eight ingredients under it tells you the total and nothing else. The caffeine could be most of that number, and usually is, because caffeine is the cheapest thing in the bag.
If you cannot see a dose per ingredient, you cannot check any of the above.
What to do
- Find the caffeine number first. Then compare the price to what caffeine costs on its own.
- Check the doses against the ones above. If green tea extract is in there at 50mg, it is on the label for the label's sake.
- Add it to your daily caffeine total. A fat burner plus a pre-workout plus coffee adds up fast, and the caffeine calculator does that sum.
- Walk away from proprietary blends. Not because the product is necessarily bad, but because nothing about it can be verified.
Related reading: is c4 pre-workout worth it and can you take too many supplements.
Verdict reads the panel and does this for you. Photograph the supplement facts label and it pulls every dose, compares each against the amounts used in published research, and flags what is underdosed or unproven. It reports the arithmetic. It does not tell you what to take.
