Weight loss: what really works (and the false promises)
No supplement burns fat. Weight loss hinges on a single, essential principle: burning more calories than you consume. That said, some supplements do offer a little extra help — whilst others are mostly just marketing hype. Let’s sort through the facts, based on the research.
The real key: the calorie deficit
Before we talk about supplements, let’s get the basics straight: it’s your calorie balance that matters most. The priority is therefore to work out your needs, then create a moderate calorie deficit whilst ensuring you get enough protein so you don’t lose muscle as well as fat.
Start by estimating your maintenance calorie intake, then aim for a reasonable deficit. It’s this figure, not a supplement, that makes the difference.
Calculate my requirementsSomething that helps a bit: caffeine
Caffeine is one of the few supplements whose benefits during exercise are well established: it improves endurance and strength, and, above all, it reduces the perception of exertion — so you train a little harder, which helps you burn more calories. As for its ‘fat-burning’ properties, the direct effect remains modest: a study on a green tea–caffeine blend showed improved weight maintenance through thermogenesis and fat oxidation, but we’re talking about a boost, not a solution.
Use with caution: around 3 mg per kg of body weight is sufficient to achieve the benefits, whilst high doses (above ~6 mg/kg) mainly increase the side effects — primarily palpitations and sleep disturbances.
Did you know that?
What protects your muscles: protein
When you’re in a calorie deficit, there’s a risk of losing muscle as well as fat. This is where a high-protein intake makes a difference: it helps preserve muscle mass whilst you’re losing weight and keeps your appetite in check more effectively. Whey isn’t a fat-burner, but it’s a handy way to get your protein without blowing your calorie allowance — exactly what you need when you’re eating less.
The false promise: L-carnitine
L-carnitine is the classic ‘fat burner’. The selling point seems logical: it transports fatty acids to the mitochondria to be burnt. However, this actual biochemical role does not mean that taking it leads to weight loss. In our studies, L-carnitine has mainly been tested in medical contexts (cancer, dialysis, coronary heart disease), not as a weight-loss aid for healthy people.
Even more telling: a controlled trial showed that 2 g a day did not even alleviate fatigue in patients — even when they were genuinely deficient. In other words, for the general public, there is no evidence of a slimming effect. It isn’t dangerous, but it isn’t the quick fix that the adverts would have you believe.
The verdict on ‘burners’
In summary
| Lever | Effect on weight loss | Verdict |
|---|---|---|
| Calorie deficit | The unique engine | Essential |
| Caffeine | A slight boost (exertion, thermogenesis) | Useful in small doses |
| Protein / whey | Help maintain muscle mass and a feeling of fullness | Useful when in deficit |
| L-carnitine | No proven slimming effect in healthy subjects | Not to be considered as a ‘burner’ |
So the best ‘slimming pill’ is still a well-balanced meal. Keep track of your daily intake with our food diary to stay within your calorie deficit without randomly depriving yourself.
Every statement in this article is based on the study summaries referenced in our caffeine, whey and L-carnitine fact sheets, where you will find the original sources. This is for information purposes only and is not a substitute for medical advice.