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Guest Article By Matthew Smith

Caffeine is the world's most popular stimulant, it is used habitually to 'wake us up' when we're tired, to drink socially, and to help us concentrate when studying or working hard. But what about caffeine as a supplement? It is one of the most heavily researched drugs there is and the benefits on performance (and in general) are still being discovered today.

This article will look at some of the most well-known benefits of caffeine, and teach you how to apply them to your diet, for maximal effect.

Benefit 1. Fat loss

Caffeine supplementation can have a huge effect on fat loss, for starters it has been shown to increase 24 hour energy expenditure [1][2]. A study by Astrup et al (1990) found that caffeine increased metabolic rate [3], whilst a study on Oolong tea found that caffeine increased fat oxidation [4]. Fat oxidation is the term used for body fat being used as an energy source, it essentially means fat burning.

So caffeine increases your metabolism, this will mean you are burning more calories per day (even if it's only a few). This on its own would lead to fat loss, but as you will find out in the following points, by increasing performance it means that you will burn more calories through exercise as well.

Benefit 2. Increased Power

A study by Lane et al (2013) found that caffeine, even when taken in low doses can improve power, the study looked at cycling power output and found that a dosage of 3mg/kg increased power by up to 3.5% when compared to a placebo [5]. This might not sound like a lot of difference, but it could be responsible for the new one rep max you manage next time you deadlift.

Another study found that caffeine could help battle the negative effect on performance of training in the morning [6]. Whether you are an early bird or a night owl, training early will decrease power output due to your circadian rhythms, ingesting caffeine can equalise this, allowing you to train in the morning with no ill effects.

Benefit 3. Improved endurance

Long distance runners could benefit from caffeine supplementation as well as gym goers. Burke (2008) found that caffeine in low to moderate amounts can improve endurance performance [7].

Another study on cyclists performing a 40km race found that those who took caffeine prior to the event reduced their time significantly [8], what makes this study interesting is the distance and time involved. It really shows how long caffeine can stay in the system whilst still benefiting the performer.

Benefit 4. Improves sprint performance

Not only can caffeine improve your endurance performance, it has also been shown to improve sprint performance - and repeated sprint performance (think HIIT). This is probably not too surprising considering caffeine's demonstrated effect on power output. Wiles et al (2006) found that caffeine improved short-duration high intensity exercises such as sprinting or cycling [9].

Another study found similar results on both time and overall volume of interval sprinting [10] (volume would mean the amount of distance covered during the sprints). Whilst Schneiker et al (2006) found that caffeine improved peak power during sprints by 7%, it also found that total volume increased 8.5% [11].

The most obvious benefit for increasing your sprint interval speed and volume, would be for people who participate in high intensity interval training (HIIT). As HIIT can also improve endurance [12] and burn fat [13] this could lead to a real one-two combination with caffeine.

Benefit 5. Lowers RPE

This is an interesting one because the previous two benefits could have been created by this one. RPE stands for rate of perceived exertion and it is used to gauge how difficult you are finding an exercise.

There are a surprisingly large number of factors that can influence how difficult you perceive an exercise to be. Mood and fatigue are the main ones, and both can be altered with caffeine [14][15][16]. So if you consume caffeine and it banishes your fatigue you will feel more energised and your workout will improve.

But caffeine can also lower pain which means that you will perceive that a weight is easier to lift, which could lead to a new one rep max. This was made clear by a study on grip strength to exhaustion where reported pain was lessened in the caffeine group [17].

Benefit 6. Can help you train better whilst sleep deprived

This was alluded to earlier, and is probably the most obvious benefit of caffeine on performance, a study by Cook et al (2012) found that athletes who were suffering from minor sleep deprivation performed significantly better than athletes who took the placebo [18]. So if you've had a bad night's sleep make sure to caffeinate yourself before a workout.

Caffeine dosage 4-6mg/kg

Now we know why you should be taking caffeine, we need to look into how. Firstly dosage, if you want optimal results you can't just estimate your caffeine intake. You need to use the correct amount for you.

Most studies tend to use around 4-6mg/kg [10][15][19] and a study by Desbrow et al (2011) found that higher doses of caffeine don't tend to make much difference to your results (and could be responsible for some negative side-effects) [20].

Just a quick note whilst we are on the subject, if you are wondering what mg/kg means. It is simply how many milligrams of caffeine to take per kilogram of body weight. So 4mg/kg for a 70kg person would be 280mg of caffeine which is about 1.5 black coffees (out of a regular sized mug).


When to take caffeine is also crucial, and the answer may surprise you. Studies have shown that you should take your caffeine one hour prior to performance [10][21][22]. So whilst most people knock back their pre-workout about 10 seconds before their first set, science tells us that this is wrong.

One distinction that should be made however, the dosages of caffeine that are used in studies are very high. 4-6mg/kg is not a usual dose of caffeine. If you are having a lower dose, then you could probably take it 20-30 minutes before training.

Benefits of Caffeine Tablets over coffee

Whilst drinking coffee can be enjoyable, it is most certainly not the optimal source of caffeine for a number of reasons. Firstly, most people don't enjoy a black coffee with no sugar they have it with milk which can actually make it quite high calorie.

Also, when dealing with high levels of caffeine (300mg+) you might end up needing to drink quite a lot of coffee. Secondly, from a convenience point of view coffee can be troublesome. It can't be knocked back in the car before driving to the gym - well it can be, but not easily!

The main issue with coffee though is how unreliable it is, when measuring exact doses coffee ends up being impossible to accurately guess. A study on speciality coffees found that the same coffee (from the same store) bought on different days produced markedly different caffeine values. Ranging from 259mg to 564mg! [23], this would give you completely different results each session. Taking a measurable and reliable tablet can remove all of the stress.

A study comparing the effect of coffee and a caffeinated alternative on endurance exercise found that there was no difference in performance between the two. Though both produced significantly better results than the placebo and decaffeinated coffee groups [24]. This study proves that other sources of caffeine are just as effective as coffee when it comes to performance.

Too much of a good thing?

After seeing the many benefits of caffeine, and some of the high doses used to improve performance you may be tempted to increase your caffeine intake, believing that more caffeine equals more energy. But it is important to recognise that caffeine doesn't actually give you energy, a cup of black coffee only contains 2 calories!

The well-worn fact that an apple will give you more energy than a cup of coffee is technically accurate, but misses the point. You see what caffeine does is mask fatigue rather than give energy. An important distinction to make.

Here's a quick guide to how caffeine works. During the day a biochemical compound called Adenosine begins to build up. Adenosine levels are measured by Adenosine Receptors, and the more Adenosine there is the more tired you become. When you consume Caffeine it attaches itself to Adenosine Receptors (who can't tell the difference) and blocks the path of Adenosine molecules.

This prevents you from getting tired and will increase your metabolic rate as the cells are no longer being told to slow down (one of the functions of Adenosine). This also causes the body to release a hormone known as Adrenaline, which will temporarily give you more energy.

A study by Chou et al (1985) found that caffeine tolerance occurs when the brain increases the number of Adenosine Receptors [25] in reaction to caffeine, this means that the same amount of caffeine ingested as before would not block enough Receptors to prevent tiredness. This means that to feel the same way, the caffeine taker would need to up their dosage.

Upping your caffeine dosage can lead to many issues, as high caffeine intake can lead to panic attacks [26], Hallucinatory experiences [27], or even hospitalisation [28]. Chronic caffeine use will eventually lower sleep quality, which will leave you overly-tired throughout the day.

So how can you prevent this? You can lower your daily caffeine dose until your tolerance goes back down (this may take a few weeks) and then treat caffeine with a bit of respect.

Used correctly, caffeine can provide all of the benefits mentioned above (plus many more, too numerous to mention here). Abuse it, and the benefits will vanish, to be replaced by tiredness, fatigue, and irritability.

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