I measured my brain waves and task performance on caffeine- here’s what I found
Originally published in April 2015 on johnfawkes.com. Note that any present-tense phrasing in this article really refers to me two years ago.
For the last six weeks I’ve been conducting an experiment on myself. I took different levels of caffeine every day, with the intent of figuring out exactly how much I should take for optimal mental and physical performance.
I was a caffeine addict for most of my life (you can read about one strategy I used to overcome that here), so it’s only recently that I’ve started to view it as a performance enhancer, rather than a problem to get rid of. However, caffeine has some very well-established physical and mental benefits that I’ve been eager to reap for myself. The results so far have been promising.
I used several methods to test caffeine’s effect on me. First off, I used my Versus EEG headset to measure caffeine’s effect on my brain waves and how it helps or harms my ability to enter a calm and focused mental state. Following off of that, I measured my productivity at knowledge work tasks on varying levels of caffeine.
I also tested the physical effects of caffeine, in two different ways: by playing sports (mainly dodgeball) and by lifting weights in the gym.
Did I find my ideal caffeine dosage? Actually, I found several ideal dosages. Before I go into my results, let’s start with the usual disclaimer around self-experiments: I only ran this test on myself, and so the results can’t be clearly generalized from me to you. Your ideal dosage may be higher or lower. I am a 30 year old man weighing in at about 152 pounds right now, so bear that in mind as you read this.
Part 1: Effects of caffeine on my brain waves
Caffeine has been reported to increase the strength and frequency of beta brain waves, which are associated with high alertness and fast thinking. Versus allows me to test that for myself, as it includes a feature that displays my levels of alpha, beta and theta waves in real-time. Unfortunately, at present Versus doesn’t add up the different levels of each brain wave and show me the data; it just shows me a rolling window of about ten seconds, so I have to eyeball the data.
Since this is a fairly inaccurate method, I spent weeks repeating this experiment, consuming some caffeine, waiting, measuring my brain waves, consuming more caffeine, waiting for it to kick in, measuring my brain waves, and so on. And while I can’t quantify my findings here, it did indeed seem that caffeine increased the level of beta waves. The effect only became clear when I went over 200 mg. Effects on alpha and theta waves were unclear- I occasionally thought I saw one or the other going up or down, but I eventually concluded that this was just noise.
In addition to measuring raw brain waves, I looked at my performance in the Versus brain-training games. I’m on the stress training program, so my goal right now is to boost my alpha waves while limiting my beta and theta waves. You would think this would mean caffeine impairs my performance, right?
Not entirely. Instead what I found was that my performance was ideal when I had consumed 75–150 mg of caffeine. More caffeine produced the expected drop, but less caffeine also lead to sub-optimal performance. Worth noting: I ran most of these tests in the late morning.
Part 2: Effects of caffeine on mental tasks and productivity
Aside from writing this blog, I work from home, self-employed, as a marketing consultant. It’s easy to get distracted in that situation since nothing stops me from goofing off, so I’ve long experimented with ways to stay on task. Using a point system I’ve been experimenting with to gamify my productivity, I measured the effect of caffeine on my work performance.
The results were pretty similar to what I found with Versus- I was most able to get work done at doses between 75 and 150 mg. If I didn’t have at least 75, particularly in the mornings, I’d usually have low energy, making it harder to motivate myself to work or just causing me to work really slowly.
At the other end, my productivity started to drop off somewhere between 150 and 200 mg of caffeine, as higher doses gave me so much energy it became hard to focus. At that range and above, I become increasingly prone to distraction, as well as experiencing a growing urge to get up and engage in physical activity.
Part 3: Effects of caffeine on sports and exercise performance
Caffeine has well-documented benefits to physical performance, with 200 mg being a typical dose for supporting fat loss, whereas most studies suggest a much higher dosage for enhancing strength and athletic performance. I didn’t test caffeine for fat loss, but I did test it for strength and sports.
First off, weight-lifting. Studies typically recommend 500 mg of caffeine to enhance strength, and pre-workout supplements will typically provide either around that much, or more commonly a lower dose mixed with other stimulants. I found 500 mg to be way too high- my heart raced, I felt dizzy, my body temperature skyrocketed, and I just wanted to lie down and let it pass.
However, I did find that lower doses of caffeine give me a noticeable boost in the gym. I start to feel an effect around 200 mg- increased energy, strength, muscular endurance, and a desire to engage in physical activity. The effect gets stronger as I raise the dosage, but higher dosages also make me feel aggressive and irritable. 400 mg seems to be my limit before I get dizzy and kind of sick, with 300 mg being my sweet spot for weightlifting.
I also tested caffeine while playing sports, mainly dodgeball, which I played most Tuesday nights. The ideal dosage for that ended up being somewhere between the ideal dosage for weight training and work, which makes sense since dodgeball is both a mental and physical task. I got my best results around 150–250 mg. Higher doses started to be counterproductive as they made it harder to think straight- my situational awareness would suffer and I’d get hit by balls I didn’t see coming. Over 300 mg, I would feel hot, my heart would race, and my stamina would start to suffer as well.
The other problem: high doses of caffeine would impair my sleep, because I played dodgeball later at night- nine to eleven PM. So I’ve backed off from higher doses and started playing on only a hundred or so milligrams to keep myself sleeping well.
So how much should you take?
Quick recap of my results:
Mental tasks: 75–150 mg
Sports: 150–250 mg
Weight training: 250–400 mg
And again, at the time I was a 30 year old male*, 152 pounds, around 13% body fat. The effects of caffeine definitely scale off of body weight, probably more so for physical than mental effects.
*To be clear, I’m still male, but I’m bigger and older now.
As guidelines to help you find your own ideal dosages, I’ve taken notes of how I felt at each level. Aside from actually measuring your performance, I think it helps a lot to go off of how you feel.
For mental tasks, like office work, you want to take just enough caffeine that you feel fully awake and alert. If you start to notice elevated heart rate or temperature, fidgeting, or you get scatterbrained and find it hard to focus on just one thing, you’ve probably taken too much.
For mixed mental and physical tasks like sports, the ideal dose will be a bit more than that. You should start to notice an elevated heart rate and maybe some temperature elevation, but not much- you want a physical boost, but you don’t want your body wasting too much energy. You also don’t want to take so much caffeine that it gets hard to focus, stay aware of your surroundings, or you feel dizzy.
For fat loss, you actually do want your body to waste energy, and don’t care too much about the mental effects. Take enough caffeine to feel a noticeable rise in heart rate and temperature, but not so much that you start to feel bad. Bear in mind, if you’re taking caffeine for fat loss you’ll be taking it every day for weeks or months, so it needs to not make it hard for you to function. Caffeine also suppresses your appetite- that’s good in moderation, but you do need to eat when losing weight. No starvation diets!
For pure strength training, a higher dose is called for. Take enough caffeine that you feel a definite rise in heart rate and temperature, and a very compelling urge to engage in physical activity. In other words, you should be bouncing off the walls. It’s alright if you feel a bit aggressive, irritable or scatterbrained at this dose, but it still shouldn’t make you feel unpleasant, like your heart is going to burst, or like you want to lie down until it wears off. Also make sure it doesn’t disrupt your sleep, particularly if you work out later in the day.
Now, the effects of caffeine on sleep vary widely between individuals, depending on your tolerance and how fast you metabolize caffeine, which is largely genetic. I metabolize it slowly, my tolerance has gone down a lot in the past year, and I have a history of insomnia, so I need to cut out caffeine fairly early in the day. Other people can have a Red Bull right before bed and sleep just fine.
If you want to try this but you truly have no idea what your caffeine tolerance is, be conservative. Start at no more than half the dosages that worked for me, and work your way up gradually, hour by hour and day by day. Remember that caffeine can take up to a half hour to kick in.
What works for me isn’t guaranteed to work for you, but unlike most supplements, caffeine has well-documented and fairly consistent effects. In other words, it’s bound to do something to you. I hope my experiments will serve to inspire some of you to start experimenting on yourselves, finding out what makes your body perform at its absolute best, and caffeine is a good place to start.
Final note: This article was originally published over two years ago. Since that time, my caffeine tolerance has gone down. I suspect if I re-ran this experiment, I’d find all of my ideal dosages to be about 20–30% lower. Your response to drugs does change over time, so while experiments like this are great to do, the results can and do become outdated.
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