20 Years of Research on Willpower Debunked! What Changed & What it Means For You

As I read the words, I felt sick to my stomach…

“20 years of research on willpower may have just been debunked.”

They were referring to the concept of ego-depletion which I prefer to call willpower fuel.

Ego-depletion was theorized by Roy Baumeister in 1998 when he did the famous “cookies and radishes” experiment. In the experiment, participants had to use their willpower to resist the urge to eat cookies on the table in front of them, and eat radishes instead.

Afterward, these participants showed significantly less persistence to complete a challenging puzzle than the participants who could eat the cookies. The big idea from that experiment was that when you expend your willpower on one thing, you have less left to take on another. 

It is a resource that gets "depleted."

He and many other researchers then confirmed this theory by replicating the experiment with different willpower challenges, types of “fuel,” and exercises. In total, over 100 studies were published over the next 18 years with similar results.

However, a study was just released claiming there is no connection between “fuel” and the strength of your willpower. [1]

Here's what was discovered, how scientists got it so wrong, and what it means for your willpower.


In 2007, Evan Carter—a graduate student at the University of Miami—tried to fuel the willpower of participants by using sugar-full lemonade (a popular willpower fuel used by researchers due to the quick spike of energy it provides to the brain).

However, Carter could not find any difference in the willpower of people who drank the lemonade, versus those who drank lemonade with artificial sweetener (which wouldn’t provide any change in blood glucose or energy).

He repeated the experiment over and over again without any significant results.

So he and his advisor started questioning the idea of willpower fuel itself in 2010 by running a meta-analysis of all studies on ego-depletion. After conducting the study he and his advisor found a significant “publication bias."


In this case, a publication bias means that over the near 20 years of ego-depletion studies, the only ones that would make it into published journals are those which confirmed ego-depletion in their participants.

Experiments like the one Carter conducted with lemonade that could not confirm ego-depletion, wouldn’t make it into published journals because the experiment essentially "failed."

So after analyzing the whole body of studies, including those that didn’t get published, he found little to no significant evidence of ego-depletion. [2]

This analysis led many other researchers in the field to challenge the whole concept of ego-depletion, or at least its relative impact on our willpower. This led to the latest study in which they tried replicating all of the ego-depletion experiments with no significant results.


If we accept that ego-depletion is at least relatively insignificant, then the question becomes, how did over 100 studies get this wrong?

Well, as a science, psychology is one of the least “black and white.”

Humans are complicated. There are so many aspects of our thinking and behavior that are left up to interpretation. This interpretation is so varied, in fact, that when one research team tried to replicate 100 psychological experiments, only 40% of them were confirmed! [3]

Let's take the poster-child of psychology, Sigmund Freud, as an example of how interpretation can go awry. Freud had many crazy ideas by today’s standards. These include his belief that all males have an “Oedipus complex” and that all females have “penis envy.”

Amazingly, people accepted many of these ideas at the time. This was because Freud could always explain behavior of people through his ideological framework. He could look to past behavior of individuals and figure out a way to explain it through his ideas. [4]

In the same way, psychologists with the “ego-depletion” framework could always explain the behavior of their participants through that idea. This allowed them to claim ego-depletion was taking place in experiments where there was, perhaps, another phenomenon going on.  


So what does this really mean? Is the entire Willpowered body of work completely ruined?

Well, unfortunately, some of it is.

My interpretation of the science of willpower has always been a mixture of biological factors (which usually rely on the ego-depletion idea) and psychological factors (which don’t).

Biological examples:

  1. What Fuels Willpower?
  2. 10 Best Foods for Long-lasting Willpower
  3. Willpower is a Limited Resource

Psychological examples:

  1. Want Power—How to Tap Into Your True Potential
  2. The Overwhelming Power of Small Wins
  3. The Extraordinary Value of Identity on Your Willpower

When I first began my research, I probably believed that strengthening your willpower was about 70% biological and 30% psychological. I was here:


But as I’ve continued my research, it has become obvious that the psychological factors are more important. At the beginning of 2016, I’d say I was about here:

Today, after spending a full month thoroughly reviewing the new literature refuting ego-depletion, it looks like we’re about here:

Biological factors like what you eat, how much you sleep, and how much mental energy you’re exerting on stressful tasks, still matter. Anyone who goes to work after a poor night of sleep, or tries to exercise after a stressful workday, knows this well.

However, it seems that these biological factors are not as important to your willpower as we once thought they were.

The science today indicates that factors like finding your purpose, having the proper perspective, and breaking your huge tasks into small, manageable chunks are far more important to strengthening your willpower and reaching your goals. [5]


When I learned about the fact that ego-depletion may have little to no affect on willpower, I immediately became emotional. I was angry, embarrassed, and was on the search for any information that would tell me, “it’s okay, these researchers are all quacks—your ideas are safe.”

I didn't want to confront the fact that I was wrong. 

This reaction reminded me of a story that occurred in 1846 at Vienna General Hospital – where 1 in 6 women were dying of childbed fever. [6]

The doctors in the hospital were completely baffled by what was causing the disease. Many had theories such as the poor diets of women in Vienna, as well as the problems with the ventilation ducts in the department.

But a doctor named Ignaz Semmelweis had a completely radical idea of the cause of the disease.

He noticed that all of the doctors that were involved in the birthing process were also doing separate research on dead bodies. 

This was before the discovery of germs, so these doctors didn't sanitize their materials, use gloves, or even wash their hands between working on dead bodies and delivering babies.

So they carried all of the diseases with them, and the doctors themselves were killing the mothers! 

When he made this discovery, Semmelweis immediately began requiring that doctors wash their hands before and after performing medical procedures.

This practice saved countless lives within his department, but it was shut down quickly by the head doctor of Vienna General. He simply could not fathom that the doctors were the ones that were killing their patients.

So he ignored Semmelweis, attributed the disease to the ventilation system, and refused to adopt the new hand washing procedures throughout the hospital. Which, of course, led to more deaths and no progress. 

Embracing THE TRUTH

When I first heard of these studies, I was acting exactly like the head of Vienna General. I didn't want to confront the brutal facts, and my gut reaction was to deny it. 

Being wrong is one of the hardest things for us to accept. We attach our ideas to our sense of self-worth. And if we find evidence that our ideas are wrong, we take it as a personal attack against our character.

So we "fight back" against this new evidence by denying it, discrediting it, or searching for other evidence that confirms our original idea—which a quick search on Google will always provide. 

You must fight back against this temptation. Your ideas are a reflection of your understanding, not your character. 10 years ago, you may have held different ideas than you do today, but would you judge your past self as less of a person of character because of that? 

This new evidence has helped me realize that some of the ideas, strategies, and research that I write about are going to be wrong—and that's okay. All I can do as a writer and researcher is try my best to evaluate the latest evidence and share the findings with you. 

It's okay to not have all of the answers in life. It's not okay, however, to ignore the brutal facts, confirm our biases, and deny the truth.


20 years of research on willpower has been debunked. The evidence today shows that strong willpower relies less biological factors like food, and more on psychological factors like motivation.

When I learned that I was wrong about willpower, I wanted to ignore it, discredit it, and deny it. But being wrong about your ideas in life is inevitable. Your ideas are a reflection of your understanding, not your character. 

The only real hit to your character occurs when you decide to place your desire to be "right" over your desire for the truth.