How to Strengthen Willpower, Part 1

Jul 07, 2008

What do the following acts have in common?

  • choosing the healthy items at the breakfast buffet and ignoring the pastries and fried food 
  • smiling and saying, “Let’s see if I can help you with that,” when an angry client blows a minor issue into a major complaint
  • sticking to a budget, even after your initial enthusiasm for improving your finances has waned, and the sale at your favorite store is beckoning 
  • staying on the treadmill for the time goal you set, even though each minute is a little harder than the last


Each of these acts requires willpower—the ability to ignore temporary pleasure or discomfort to pursue a longer-term goal. It’s easy to agree that these challenges require inner strength, but where does that strength come from? And why is willpower such a fickle friend, supporting us on some occasions and abandoning us on others? 

Fifteen years ago, Roy F. Baumeister, PhD, now a researcher at Florida State University, set out to answer these questions. He pitted several possible models of willpower against each other, and when the dust of his early studies settled, the results supported a surprising model. According to Baumeister, willpower is not a personality trait, a skill or a virtue. Instead, it operates like a muscle. And as such, it can be strengthened--but also easily exhausted (Baumeister 2003).

This “strength” model of willpower has important implications for fitness and wellness professionals who seek to inspire and support healthy behavior in others. By understanding how willpower can be strengthened, you can find new strategies for helping clients meet their goals. And by understanding why willpower is necessarily limited, you can identify ways of supporting behavior change without exhausting willpower.

A strength model of willpower proposes four important ideas:

  1. Willpower is a mind-body response, not merely a mindset.
  2. Using willpower depletes resources in the body.
  3. Willpower is limited.
  4. Willpower is trainable.
Let’s consider each of these ideas; the evidence that supports them; and how they can be applied to health behaviors. In this first part, we’ll take a look at the first two.


Willpower Is in the Mind and Body
Mind-body responses are coordinated physiological changes that allow you to adapt to some challenge. The best-known mind-body response is the fight-or-flight response to stress or danger--heart racing, blood pressure soaring, muscles tightening and senses heightened (Sapolsky 2004). The relaxation response, in contrast, allows the body to respond to its internal needs of digestion, growth and restoration (Benson 1975).

Suzanne Segerstrom, PhD, a psychologist at the University of Kentucky, was one of the first researchers to study the biological basis of willpower. Segerstrom’s research has begun to identify changes in the autonomic, cardiovascular, neuroendocrine and immune systems during acts of willpower. Segerstrom says it’s possible that these changes are part of a coordinated whole-body response that helps us adapt to challenges requiring self-control. She calls it a “pause and plan” response. This mind-body response would allow us to temporarily freeze our impulses and focus on our long-term goals.

What’s going on in the body that helps us slow down and proceed with intention, not instinct? One important process is heart rate variability (HRV), or the beat-to-beat fluctuations in heart rate. In one study, Segerstrom required participants to flex their willpower by eating carrots and resisting cookies (Segerstrom & Solberg Nes 2007). Successful participants showed a temporary increase in HRV as they were exerting their willpower, followed by a drop afterward. What’s more, participants who had higher HRV when they joined the study showed greater willpower.

Why would higher HRV assist self-control? Changes in HRV are determined by the autonomic nervous system’s balance of sympathetic activation (responsible for the fight-or-flight response) and parasympathetic activation (responsible for the relaxation response). High HRV reflects a healthy, flexible activation of both systems (Appelhans & Luecken 2006). Maintaining high HRV in the face of a self-control challenge might represent a kind of inner strength and stress resilience--the ability to focus attention (as in the fight-or-flight response) but also to stay calm (as in the relaxation response). The result: acting in line with our highest goals, and not with our immediate appetites.

Willpower Depletes Resources in the Body
The mind-body response of exerting willpower literally fatigues us (Tice et al. 2007). It depletes physical power, as shown in one study that looked at the effects of mental self-control on physical stamina (Bray et al. 2008). In this study, trying to control one’s thoughts decreased muscular endurance, as measured by performance and EMG activity. The researchers who conducted this study called the effect “central fatigue.”

Our minds and bodies draw from the same source of strength. But what is this source? Matthew Gailliot, PhD, a researcher at the University of Amsterdam, argues that the fuel of willpower is glucose. In a way, this should be no surprise, since glucose is the primary fuel of the body. It’s the same fuel that skeletal muscles use to exert their strength, and the same fuel that the brain uses to perform its many tasks. What is surprising is the fact that willpower uses a lot of it, even when the body is at rest. According to Gailliot, willpower is a particularly expensive mental act, engaging many areas of the brain and requiring high levels of fuel (Gailliot et al. 2007).

Gailliot and his colleagues have demonstrated that simple acts of self-control both require and lower blood glucose levels. In one recent set of studies (Gailliot et al. 2007), participants were required to control their thoughts, emotions or behavior. Immediately following each act of self-control, participants’ blood glucose levels dropped. Levels did not drop during similar tasks in which participants were not exerting self-control. Participants were then asked to repeat the acts of self-control. Those whose blood glucose levels had dropped the most from the first task performed the worst on the second attempt. Participants given a sugary drink between tasks (replenishing their blood glucose levels) were better able to exert their willpower in the second attempt.

This study certainly pushes the boundaries of how we think about willpower. Not many of us would like to believe that our virtue is dependent on the last time we snacked. However, the implications are important: our ability to flex our willpower depends on the availability of blood glucose. When blood glucose levels are low (for example, from skipping breakfast), or when the body has impaired use of glucose (as in diabetes or the increasingly common metabolic syndrome), willpower is impaired. Numerous studies confirm that low blood glucose levels and poor glucose use are associated with worse self-control of attention, emotions and behavior (Gailliot et al. 2007).

Does this mean we should be giving ourselves sugar every time we want to exert some self-control? Clearly, that would be a short-sighted strategy. In their report of this research, Gailliot and his colleagues recommend a more reasonable strategy: choose foods that keep blood glucose levels relatively stable, and don’t skip meals.

Look for the second part of this article in the August Inner IDEA Body-Mind-Spirit Review.

Kelly McGonigal, PhD, teaches psychology, yoga and group fitness at Stanford University. Contact her at or

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