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The Anatomy of Willpower

Willpower is real. It may sound fluffy, but willpower is not a word like karma—there’s convincing scientific evidence that willpower exists.

It wears many hats. Self-discipline, self-control, self-regulation, self-denial, determination, grit, etc. Willpower is the force that you use to pay attention to a boring talk, quit smoking, hold back fury, do laundry, or spend the long weekend with your in-laws. Willpower is what you use to swim against the current of the Lazy River. It’s how you make yourself do things you don’t want to do.

For the sake of style, it’ll just be willpower from now on.

Willpower is partly innate. Differences in willpower at a very young age seem to persist for life.

One study monitored a thousand people from birth to age 32. From the tender ages of 3 to 11, they were subjected to regular willpower tests. The kids with more willpower turned into adults with more willpower—adults who made more money and were healthier, less addicted to drugs, and less likely to end up in jail.1426

Scientists are still fleshing out the details, but we know a front-brain structure called the anterior cingulate cortex plays a critical role in willpower.1427

And we know willpower is tightly linked to blood sugar. When blood sugar is high, willpower is generally high. And when blood sugar is low, willpower generally suffers.1428

This makes sense. The brain uses a whopping 19% of the body’s total energy supply.1429 Since blood sugar is the brain’s main fuel, it’s logical that when blood sugar is low, parts of the brain that aren’t essential to survival on a minute-to-minute basis (like the anterior cingulate cortex) would get less blood sugar, and slow down.

(Willpower is important, but it’s not breathing.)

And there are some uncanny links between willpower and blood sugar.

Willpower and Blood Sugar

  • Blood sugar is used most efficiently in the morning—right when willpower is the highest.1430
  • Alcohol reduces self-control (willpower), and it reduces blood-sugar metabolism in the anterior cingulate cortex (the willpower hub).1431
  • Diabetics, who struggle to use blood sugar efficiently, do poorly on tests of willpower.1432
  • It’s hard to focus (a form of willpower) when you’re sleep deprived. Sleep deprivation decreases blood-sugar metabolism in brain regions associated with attention control.1433
  • Criminal behavior is associated with both poor impulse control (a form of willpower) and poor blood-sugar control.1434
  • “Hangry” people are less able to control their emotions. Being hangry (hungry + angry) is caused by low blood sugar.

When you have low blood sugar, you have low willpower.

How Willpower Burns

Scientists study willpower with several different tests, like seeing how long someone works on an impossible geometry puzzle before they give up, or how long it takes them to yank their hand out of a bucket of ice water after plunging it in. The logic is that people burn willpower when they force themselves to do hard things.

And burning willpower leaves people with less willpower for other hard things. In one experiment, 67 college students skipped a meal and sat at a table with a stack of cookies and a bowl of radishes.1435 To maximize temptation, the cookies were baked in the testing room. The researchers let one group of students eat the cookies, but forbade the other group from eating the cookies, only allowing them to eat the radishes (poor souls).

Right after, both groups were given an impossible geometry puzzle to solve. There was also a control group who simply skipped a meal and went straight to the impossible geometry puzzle.

On average, here’s how long the different groups worked on the puzzle before quitting:


The radish group folded like a house of cards. According to the researchers, they caved so quickly because they’d already burned a blob of willpower resisting the cookies, so they had less willpower available for the geometry puzzle.

Burning willpower on one hard task (resisting cookies) left less willpower for a totally different hard task (the puzzle). In other words, willpower is general-purpose. We use it for many different things.

Kind of like money.

The question is, what will you spend your willpower on?

It’s not just obvious things, like resisting cookies, that burn willpower. For instance, making decisions burns willpower.1436 One study showed that judges were far more likely to grant parole in their first three decisions of a court session—before “decision fatigue” set in—than in their last three decisions.1437

You don’t want a hangry judge.

The following things have all been found to deplete willpower: managing the impression you’re making on someone, suppressing prejudices and stereotypes, coping with thoughts of death, controlling spending, restraining aggression, and controlling intake of food and alcohol.1438

A 2010 meta-analysis of 83 willpower studies concluded that there is “a significant effect of ego depletion on self-control task performance.”1439 In other words, this summary of 83 studies concluded that willpower is limited, that it’s depleted by hard activities, and that after it’s depleted, we do worse at other hard activities.

The Flux of “You”

It’s critical to realize that willpower is limited, and in constant flux. People fundamentally underestimate how different their future mental states will be from their present one. Psychologists call this the “hot-cold empathy gap.” It refers to the poor ability of people in a calm, collected state to predict how they’ll behave in the future—which may have churning emotions, low blood sugar (and willpower), and wicked temptations.

Studies show that this hot-cold empathy gap operates in areas as diverse as economics,1440 eating,1441 and sex.1442

It’s easy to set goals when you’re lounging on the couch watching holiday specials, your blood full of Christmas sugar, and your mind motivated to greet the New Year with a New You.

It’s hard sticking to these goals on February 18th, after a poor night’s sleep and a stressful day at work, with looming drudgeries and no major holidays (or even the weekend) anywhere in sight.

We usually set goals when we’re feeling strong, and our tank of willpower is full. We project this strength into the future. That’s why goals are often unrealistic: they don’t account for our seesawing willpower—or our delusions. Studies have found that people tend to picture their future self as a sort of idealized saint.1443

Throughout my life, I’ve always pictured my future self as a paragon of human excellence, virtuous in all the ways that I am flawed. Alas, this person still hasn’t shown up.

(But I’m expecting him any day now.)

When you’re setting goals, remember that goals take willpower, and willpower fluctuates. Don’t overestimate your future self when you’re feeling strong, or underestimate your future self when you’re feeling weak.

The point is, you are not a static entity. Your mind isn’t bedrock. It’s more like shifting sand, a 360° neuro-hormonal seesaw that’s always tilting up and down and all around. To make successful changes in life, it helps to realize that you are change.

Powering up Willpower

Willpower isn’t a simple function of genetics and blood sugar. Other factors affect willpower, too. As if we needed another reason to exercise, it’s been shown that regular exercise significantly improves willpower.1444

So does getting enough sleep.1445,1446,1447,1448

So does meditation.1449

Putting people in a positive mood increases their willpower.1450 So does having them think more abstractly, rationally, and globally.1451 Research indicates that motivation, beliefs, and incentives also affect willpower.1452,1453

In fact, believing your willpower is unlimited (and not a limited resource) has been shown to block willpower depletion in the lab, leading some researchers to speculate that willpower is “all in your head.”1454 Other studies have supported the idea that a belief in unlimited willpower makes people happier, and more likely to reach their goals.1455

But other research has shown that, while beliefs about willpower do make a difference when willpower depletion is mild, when willpower is severely depleted, beliefs don’t matter.1456 You can believe whatever you want, but willpower is still a limited resource.

Everyone needs to relax sometimes.

Even David Blaine, an endurance artist who did a medically documented water fast (consuming nothing but water) for 44 days.1457 Blaine also held his breath underwater for 17 minutes on an episode of Oprah.1458

It’s hard to imagine more incredible feats of self-control.

And yet, according to Blaine:

As soon as I’m done with that [a stunt] I go to the opposite extreme, where I have no self-control…After a stunt I’ll go from 180 pounds to 230 pounds in three months…I’ll eat perfectly for five days and then eat horrifically for ten days…I have self-discipline in work, but I have none in my life sometimes.1459

David Blaine’s epic willpower only seems to work in short bursts, after which it’s severely depleted.

If he doesn’t have unlimited willpower, neither do we.

Some studies have found that overestimating your willpower can lead to exposing yourself to more temptations than you can handle.1460 Believing in unlimited willpower may work for some goals, but the last thing you need is to believe your willpower is unlimited, get disillusioned when you eat a cookie, and then quit.

Still, recent developments in the field suggest that beliefs and attitudes play a much larger role than previously thought, and that positive thinking has real, physical power.

Get motivated.

You can do this.


Willpower is the rocket fuel we use to veer off the Lazy River and get what we want in life. It’s the mental gasoline that powers us through hard tasks. It’s our mighty agent of change.

But willpower is fickle. Like the blood sugar controlling it, willpower rises and falls, comes and goes, ebbs and flows.

And it’s often in short supply.

When we burn willpower on one hard task, we have less willpower available for the next one. After enough consecutive hard tasks, our willpower tank is empty, and we’re done with hard tasks.

Willpower is influenced by beliefs, motivation, and incentives. So believe in yourself.

(It’s science.)




1426. Moffitt et al., “A Gradient of Childhood Self-Control Predicts Health, Wealth, and Public Safety,” Proceedings of the National Academy of Sciences 108, no. 7 (2011): 2693-2698.

1427. Shenhav et al., “The Expected Value of Control: An Integrative Theory of Anterior Cingulate Cortex Function,” Neuron 79, no. 2 (2013): 217-240.

1428. Gailliot M., and Baumeister R, “The Physiology of Willpower: Linking Blood Glucose to Self-Control,” Personality and Social Psychology Review 11, no. 4 (2007): 303-327.

1429. Durnin, J., “Basal Metabolic Rate in Man,” Joint FAO/WHO/UNU Expert Consultation on Energy and Protein Requirements, 1981. https://www.fao.org/3/contents/3079f916-ceb8-591d-90da-02738d5b0739/M2845E00.HTM

1430. Gailliot, M., and Baumeister R., “The Physiology of Willpower: Linking Blood Glucose to Self-Control,” Personality and Social Psychology Review 11, no. 4 (2007): 303-327.

1431. Ibid.

1432. Ibid.

1433. Ibid.

1434. Ibid.

1435. Baumeister et al., “Ego Depletion: Is the Active Self a Limited Resource?” Journal of Personality and Social Psychology 74, no. 5 (1998): 1252-65.

1436. Vohs et al., “Making Choices Impairs Subsequent Self-Control: A Limited-Resource Account of Decision Making, Self-Regulation, and Active Initiative,” Motivation Science 1S (2014): 19-42.

1437. Danziger et al., “Extraneous Factors in Judicial Decisions,” Proceedings of the National Academy of Sciences 108, no. 17 (2011): 6689-92.

1438. Gailliot et al., “Self-Control Relies on Glucose as a Limited Energy Source: Willpower Is More Than a Metaphor,” Journal of Personality and Social Psychology 92, no. 2 (2007): 325-336.

1439. Hagger et al, “Ego Depletion and the Strength Model of Self-Control: A Meta-Analysis,” Psychological Bulletin 136, no. 4 (2010): 495-525.

1440. Loewenstein G., and Adler D., “A Bias in the Prediction of Tastes,” The Economic Journal 105, no. 431 (1995): 929-937.

1441. Read D., and Van Leeuwen, B., “Time and Desire: The Effects of Anticipated and Experienced Hunger and Delay to Consumption on the Choice between Healthy and Unhealthy Snack Food.” Organizational Behavior and Human Decision Processes 76 (1998): 189–205.

1442. Ariely D., and Loewenstein G, “The Heat of the Moment: The Effect of Sexual Arousal on Sexual Decision Making,” Journal of Behavioral Decision Making 19, no. 2 (2006): 87-98.

1443. Tanner, R., and Carlson, K., “Unrealistically Optimistic Consumers: A Selective Hypothesis Testing Account for Optimism in Predictions of Future Behavior,” Journal of Consumer Research 35, no. 5 (2009): 810-822.

1444. Oaten, M., and Chang, K., “Longitudinal Gains in Self-Regulation from Regular Physical Exercise,” British Journal of Health Psychology 11 (2006): 717-733.

1445. Christian, M., and Ellis, A., “Examining the Effect of Sleep Deprivation on Workplace Deviance: A Self-Regulatory Perspective,” Academy of Management Journal 54, no. 5 (2011): 913-934.

1446. Wu et al., “The Effect of Sleep Deprivation on Cerebral Glucose Metabolic Rate in Normal Humans Assessed with Positron Emission Tomography,” Sleep 14, no. 2 (1991): 155-162.

1447. Venkatraman et al., “Sleep Deprivation Elevates Expectation of Gains and Attenuates Response to Losses Following Risky Decisions,” Sleep 30, no. 5 (2007): 603-609.

1448. Meldrum et al., “Sleep Deprivation, Low Self-Control, and Delinquency: A Test of the Strength Model of Self-Control,” Journal of Youth and Adolescence 44, no. 2 (2015): 465-477.

1449. Friese et al., “Mindfulness Meditation Counteracts Self-Control Depletion,” Consciousness and Cognition 21, no. 2 (2012): 1016-1022.

1450. Tice et al., “Restoring the Self: Positive Affect Helps Improve Self-Regulation Following Ego Depletion,” Journal of Experimental and Social Psychology 43 (2007): 379-384.

1451. Fujita et al., “Construal Levels and Self-Control,” Journal of Personality and Social Psychology 90, no. 3 (2006): 351-67.

1452. Vohs et al., “Motivation, Personal Beliefs, and Limited Resources All Contribute to Self-Control,” Journal of Experimental Social Psychology 48, no. 4 (2012): 943-947.

1453. Hagger et al, “Ego Depletion and the Strength Model of Self-Control: A Meta-Analysis,” Psychological Bulletin 136, no. 4 (2010): 495-525.

1454. Job et al., “Ego Depletion—Is It All in Your Head? Implicit Theories About Willpower Affect Self-Regulation,” Psychological Science 21, no. 11 (2010): 1686-93.

1455. Bernecker et al., “Implicit Theories About Willpower Predict Subjective Well-Being,” Journal of Personality 85, no. 2 (2017): 136-150.

1456. Vohs et al., “Motivation, Personal Beliefs, and Limited Resources All Contribute to Self-Control,” Journal of Experimental Social Psychology 48 (2012): 943-947.

1457. Korbontis et al., “Refeeding David Blaine—Studies After a 44-Day Fast,” New England Journal of Medicine 353, no. 21 (2005): 2306-7.

1458. Sharples, Tiffany, “How David Blaine Held His Breath,” Time. 05-01-2008. https://content.time.com/time/health/article/0,8599,1736834,00.html

1459. Baumeister, Roy, and Tierney, John. Willpower: Rediscovering the Greatest Human Strength. New York: Penguin, 2011. Print. Page 140.

1460. Nordgren et al., “The Restraint Bias: How the Illusion of Self-Restraint Promotes Impulsive Behavior,” Psychological Science 20, no. 12 (2009): 1523-8.

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