This is why fat burners will f***k you up

  • By Brian Keane

I sit down and write every morning for about two hours; normally I have a good idea of what message I want to get across or topic I want to cover but today was one of those days where this topic was burning in my head so I put finger to keyboard in the hopes that it helps 😀

In episode 7 of the podcast (out on Monday) titled ‘EVERYTHING YOU NEED TO KNOW ABOUT SUPPLEMENTS’ – I talk about how I was fooled (for years) about buying every supplement that pictured my favourite fitness models or bodybuilders; my thought were ‘well if I use that supplement, I’ll look like them’ – so month after month, I’d scrape the last bit of money that I had and go and buy the new ‘silver bullet’ supplement (you know the one that turns you into a cover model in 6 weeks).

Month after month, the changes would be so minimal (and the cost so maximum) that I got very disheartened and started to do my own research on supplements. 6 years later, I’m actually a bigger fan of supplements now than I was even then, the difference is now I know WHAT ones to use and HOW to use them.

I’ve saved hundreds and probably thousands at this stage by focusing on using the fundamental supplements that work and avoid the latest ‘fat burner ripped fuel sliced abs 6000’ or ‘muscular enhancer weight gainer 5million’. After talking with one of my girls in my online program yesterday, this has been burning on my mind for the last 24 hours.


To really hedge my point, I have to say that fat burners 100% work in the short term (the short term being the operative term).

A good over the counter fat burner will give you more energy and possibly reduce your appetite. Most over the counter fat burners run off your beta 2 receptor (for example caffeine runs off the beta 2 receptor which helps you burn body fat) – but as anyone who drinks 3 cups of coffee a day can attest to, you build up a tolerance.. and quickly. So even though that fat burner was helping to give you energy (and the caffeine was initially helping to release fat from the cells), once your beta 2 receptors becomes down regulated (i.e. caffeine tolerance), the fat burner will largely stop working meaning you are spending money on very expensive coffee or wasting it all together.

My biggest issue with fat burners is probably the known ‘rebound’ that they cause in most people. It’s not uncommon to lose a bit of weight using a fat burner but to keep it off when you stop using it is another matter completely.

Most fat burners have time released stimulants (to give you consistent energy in place of food)- this is great while you are taking them, you have more energy, don’t need food to function and are more alert through the day.

I remember taking a fat burner in college (BSN Atro Phex which has since been banned) and I went to the gym for two hours (twice) and played three hours of 7 a side soccer in the evening.. on an apple.

I woke up the next day with can only be described as ‘hit by a bus’ syndrome. I never questioned where the energy came from (I had trained nearly 7 hours the previous day on about 100kcals) but it gives you an idea of the strength of some of the over the counter fat burners (I bought them in a local health store when I was buying my porridge!). I spent the rest of the week like a zombie; Alas, Isaac Newton was right ‘what goes up, must come down’.

Because fat burners send your body into a consistent state of ‘fight or flight’ – your entire recovery and hormonal system are jeopardised. If you have ever used a fat burner and got up to the go the toilet in the middle of the night only to be wide awake as soon as you climb back into your bed; its because your over active ‘fight or flight’ response.

When you wake, your body spikes cortisol (which is actually the natural way to wake up) but with the presence of excess stimulants in your system and over workings of your adrenals; this process is massively heightened i.e. its 3am, you wake and your body thinks its ready to start the day.

But what causes the rebound? There are two main reasons that generally cause the rebound:

1) ENERGY CRASH AND CRAP FOOD: When you stop taking your fat burner, you come out of a state of fight or flight (which was giving you consistent, albeit ‘fake’ energy) leaving you with an incredible drop or low. What do you tend to reach for when energy is at an all time low? You got it: food. And it’s normally not broccoli, porridge or chicken either; when that ultimate energy low hits us, its sugars, chocolate, biscuits, cakes or other stimulant drinks that we reach for. From a basic calories in, calories out (taking hormonal response out of it, as they have also been affected) leads to = rebound.

2) YOUR APPETITE COMES BACK HARD! Most fat burners (the good ones anyways) normally include a strong ‘appetite suppressant’ – and they do as the name suggest, they suppress your appetite.

That’s fine while you are taking them, but think about what happens you come off them? Your appetite has been supressed for 6-8 weeks? I like to think of it like pulling back a rubber band, the harder and longer you pull it back (appetite suppressed), the further it rebounds back.

48 hours after the Atro Phex / 7 hours of training on only an apple situation that I mentioned above, I was utterly ravenous! I must have consumed 10,000 – 12,000 kcals two days later. It also doesn’t take a rocket scientist to realise that if I was trying to lose body fat, one day on 100 kcals and another on a 12,000 kcals probably isn’t going to support me all that much.


As I mentioned above, this is what over the counter fat burners can do; just because you can buy it in a local shop (most aren’t FDA approved anyway), doesn’t make it good or safe for you. I can go to any fast food shop and buy cheeseburgers every day, that doesn’t make it good for me. We have an availability bias in our brain (its one of the 25 cognitive bias that we evolved) and we think that because its available, it must be ‘okay’ – remember not too long ago, you could buy opium on the open market (and heroin is derived form the morphine alkaloid found in opium) so don’t ever use something just because you can buy it over the counter.

I know all of this from first hand experience. I must have experimented with every fat burner on the market from 19-23 and had all the positive and negative effects that came with them. One of my favourite quotes is ‘smart peole learn from their mistakes, really smart people learn from other peoples mistakes’. The advice I would offer is ‘be really smart person’.

The key to losing fat is to find a good nutritional plan and training program that are in alignment with your goals. There are fat burners like green tea extract and l-carnitine that wont mess you up mentally, physically or philologically and will support your fat loss efforts; but unfotuntatley as I’ve found, there are no ‘silver bullets’ but I promise you, if you lose fat the right way, you will lose it and keep it off!

Brian Keane Fitness Podcast

Brian is a qualified personal trainer, sports nutritionist and strength and conditioning coach.

He is the best selling author of the book The Fitness Mindset and currently travels the world as a professional speaker. He also hosts the #1 podcast The Brian Keane Podcast.

Follow Brian on:


The Fitness Mindset BookRewire your Mindset Book