The Placebo Effect

The Placebo Effect

Hey friend!

I want to do something a little bit different today. I want to open with a review of a study (it was a big one in the field, citation at the end), and then discuss the implications. 

Let’s get in to it.

What did they do?

They wanted to examine the effects of caffeine at varying doses on cycling performance. They took well-trained male cyclists and had them complete a total of five 10 km cycling time trials (which simply means ‘hit 10 km as fast as you can’). Two trials were control trials to see how they would perform without the caffeine. For the three experimental trials, the cyclists were given placebo, 4.5 mg/kg caffeine, or 9.0 mg/kg caffeine, in a randomized order. 

Let’s take a quick second to review these doses. Placebo is zero – no performance enhancements from caffeine should appear. The units mg/kg are used to indicate that the dose was scaled based on their bodyweight. Bigger individuals need more caffeine than smaller individuals to receive the same effect. They calculated out the cyclists’ weight in kg and multiplied by the given number (for example, a 100kg individual doing the 4.5 mg/kg dose trial would have been given 450 mg of caffeine). 4.5 mg/kg is right in the middle of the typical recommended dose (3-6 mg/kg) for physiological benefits. On the other hand, 9.0 mg/kg caffeine is very high. Like, ‘my hand is shaking’, kind of high.

So what happened?

When you look at the three experimental trials, you see a clear dose-response relationship for both power output and performance. Basically, as the dose of caffeine got higher, they were able to push and work harder. Because they were able to work harder, they had better performance.

Specifically, the 4.5 mg/kg group saw a 1.3% improvement, while the 9.0 mg/kg group saw a whopping 3.1% improvement. Over a 10 km distance, that translates into the other guy being 1-3 football fields behind you!

Why did you want to review this study?

Well, I lied to you earlier. And so did the researchers to the cyclists.

The truly fascinating thing about this study was that no cyclist was given caffeine in ANY trial, despite being told they would. They received placebo in all three trials.

The placebo effect is a known phenomenon, but is still not a well-researched topic. And this study was the first to show that, not only was a placebo effect present, but that it could have a dose-response relationship. The strength of the cyclists’ belief determined the strength of the performance improvement!

Mind blown.

Another interesting observation from the trial that I omitted before – the placebo group did worse than the control trials. Being told they were given placebo made them do worse than they were naturally capable!

The brain is the master regulator for everything. And what your brain thinks is real frequently becomes real.

Tell me a little bit more about the placebo effect


The placebo effect is believed to be a significant component of why there is an individualized response to everything. In the realm of nutrition, we see a big variability in responses to diets, foods, and supplements. Many substances have what are called ‘responders’ and ‘non-responders’. For example, some people do great with caffeine, other people see no benefit, and still others see a detriment. Yes, there are other ‘legitimate’ factors, like your genetics (I discussed a relationship between genetics and caffeine use in a previous newsletter). However, even when all other factors are accounted for, we still see a big variance. The placebo effect is now believed to account for a big portion of this gap. 

There is another closely related concept called the nocebo effect. It is the same as the placebo effect, but in the opposite direction. While the placebo effect causes a benefit based on your belief and expectations, the nocebo effect causes a detriment. If you believe something bad will happen, you increase the chances that it will.

Final thoughts

I’m a big fan of the placebo effect and I leverage it whenever I can. If there is something that is rooted in sound nutrition practice, I’ll hype it up. This will increase the expectancy in the listener, and increase the chances that it will be beneficial. Similarly, if a client tells me they have so-and-so amazing product that has done wonders for them, and I know it’s baloney but won’t do them any harm, I don’t need to correct them. If they think it’s helping, it probably is.

The nocebo effect is very tricky when you’re ‘in the know’. You need to not let yourself believe too strongly that things are going to be bad for you (easier said than done, I know). 

I’m getting a tad bit philosophical here – but my real recommendation to you is to simply be optimistic. You ever notice how good things seem to follow the optimistic and bad things follow the downers? This effect explains why.

Let me know what you thought of the format this week ( If you liked the research review style, I can do more of them. Either way, I’m looking forward to chatting again next week.

Take care.


PS – You’re going to have an amazing weekend, I KNOW it. But do you? (Yes, I’m trying to placebo you.)


Beedie CJ, Stuart EM, Coleman DA, Foad AJ. Placebo effects of caffeine on cycling performance. Med Sci Sports Exerc. 2006 Dec;38(12):2159-64. doi: 10.1249/01.mss.0000233805.56315.a9. PMID: 17146324.