There’s a lot of talk both online and in the gym on the use of fat burners, so I’ve dug deep into the scientific research of the key ingredients commonly found in them. Here’s my definitive say on what fat burners are and how they work.
Firstly, let me begin by saying:
They’re Not a Quick Fix!!
If you saw an advert for a magic pill, that you could buy without a prescription, that promised to literally melt your fat away whilst you did nothing, you’d probably be fairly sceptical. And quite rightly so, because this magic pill doesn’t exist. (Sadly.)
Having said that, there is a place in every gym bag for fat burners. But the gym bag is a must. Consider it a vital added ingredient. As no fat is going anywhere without a decent, high intensity workout a few times a week, alongside a healthy, high protein diet. When taken as part of a diet and exercise regime, they will indeed help shift fat and build lean muscle.
But since you’re here at Fitness Savvy, you’re probably already fitness and diet aware, and you’re looking for some no-nonsense advice on whether fat burners are for you.
So with that important note covered, let’s get into the nitty gritty…
Okay Edd, What’s in Fat Burners?
Each brand has its own unique blend of fat burning ingredients but they usually contain some or all of the following:
- Conjugated Linoleic Acid (CLA)
- Caffeine (often listed as green tea, or green coffee, extract)
- Raspberry ketones
- Cayenne pepper
These are all stimulants that help you burn more calories as heat (thermogenesis) when you’re exercising. Some work by increasing your metabolism, some by upping your body temperature and energy levels and some by stabilising your appetite and reducing cravings. They often work hand in hand, better as a combination, than when taken alone. 
Conjugated Linoleic Acid
A type of omega 6 fatty acid naturally found in beef, lamb, dairy products and flax seeds, CLA is added to fat burners for several reasons:
It’s thought to reduce the number of calories, and therefore food, required to work out, and it increases energy expenditure. It’s also thought to increase lipolysis (the breakdown of lipids, or fats) and fat oxidation (the process of fat being broken down into its constituent parts – fatty acids). All resulting in fat loss.
A study in 2007  concluded that CLA, when taken in conjunction with creatine (ideal then, if you’re also taking creatine supplements) leads to an increase in fat loss and therefore also in fat free body mass, when combined with resistance training. The study also found muscular endurance to be improved.
Caffeine is a much-studied element in sports and exercise science. It’s perhaps the most used ‘drug’ in the world, is mostly free from side effects (unless you consume too much, and we all know what that feels like) and yet it’s the most understated fat burner around.
Caffeine works by increasing fat oxidation  both during exercise and at rest (plus its obvious energy giving properties to fuel a workout are not being overlooked here). It is thermogenic, meaning that it increases body temperature which in turn burns more energy as heat.
But in order for thermogenesis to be optimal, you’d need to drink more than eight strong cups of coffee a day. That’s why caffeine extract is usually added to fat burners, as it’s a more concentrated way of consuming it. We certainly wouldn’t fancy working out on a bladder full of pints of coffee…
As an added extra, caffeine is often included as an extract of green tea, which is full of immune boosting antioxidants.
The jury is still out on the effectiveness of raspberry ketones as a fat burning compound. Most studies have involved rats and very high doses of raspberry ketones, so the evidence is sketchy when it comes to humans and a sensible dose.
A study in 2013 in the Journal of the International Society of Sports Nutrition  looked at the effect of a specific supplement on fat loss. The supplement contained raspberry ketones along with caffeine, capsaicin (responsible for making chillies hot), garlic and ginger.
It concluded that after eight weeks of supplementation “beneficial changes in body composition and anthropometric variables (hip and waist girth) in overweight men and women” were seen and furthermore “additional benefits on energy levels and food cravings” were recorded.
Yep, we hear your cries of “yeah Fitness Savvy, great but how do you know it was the raspberry ketones and not everything else which led to these results?”
Well we, and the authors of the study, don’t. But as there are no known side effects of raspberry ketones (backed up by participant findings and blood tests in this study) it’s probably not a bad thing to add them to fat burners.
Cayenne pepper (which contains capsaicin) is known for its thermogenic, fat burning properties.
A 2015  study in the same journal looked at the efficacy of a fat loss supplement containing cayenne pepper (and green tea extract among other things).
It found that the supplement, when taken before exercise, had positive benefits on fatty acid oxidation, hunger and stamina, therefore suggesting “an acute effectiveness in improving exercise-related fat loss benefits”.
Again, more evidence to suggest when certain thermogenic ingredients are combined, they work better to burn fat.
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Awesome! So How and When Do I Take Fat Burners?
Crucially, if you want decent sleep (critically important if looking to stay healthy and prevent muscle atrophy, as explained here) then take them early in the day. As they contain caffeine and other stimulants, which are great for an energy boost to power your workout, they’re bad news for sleep. We don’t advise taking them after around 2pm.
Follow the instructions on your chosen fat burners, but they’re generally recommended as a pre-workout supplement. Most suggest taking them for a few weeks, then having a couple of weeks off before starting the cycle again.
Any Safety Precautions I Should Know About?
Sticking to fat burners containing any combination of the ingredients we’ve just discussed, and following the dosage instructions, will make sure you’re safe. Taking too many could cause dizziness and heart palpitations which can be pretty scary.
If you have heart problems, you’re sensitive to caffeine or you have any other health concerns you’re worried about, speak to your doctor before taking fat burners. Stop taking them if you notice more than just ‘coffee jitters’.
Our Fat Burner Price Comparison Page contains a huge range for you to check out!