Dieting and willpower: It’s not just about hunger and palatability.

I had the pleasure of discovering the book “Willpower: Why Self-Control is the Secret of Success” by Roy F. Baumeister and John Tierney. The authors' premise is that all successful people possess two qualities: intelligence and self-control. They believe people can improve their ability to resist temptation and provide methods to achieve this lofty goal. However, I’m going to concentrate on the research the authors provide to help us better understand what willpower is and how it works.

The book transforms willpower from an abstract concept into a tangible and predictable real-world phenomenon. The primary methods to understand willpower are experimentation and observation. The results are unavoidably subjective compared to other more “concrete” areas of science. Nevertheless, it’s refreshing to see the problem tackled with biology and falsifiable experimentation rather than a treatise expressed in purely philosophical terms.

The Radish Experiment

The effect of willpower on a human’s ability to perform tasks was tested using an unusual and slightly cruel experiment.

The experimental subjects sat down at a table with several culinary choices: the warm cookies, some pieces of chocolate, and a bowl of radishes. Some students were invited to eat the cookies and candy. The unlucky ones were assigned to “the radish condition”: no treats, just raw radishes.

To maximize temptation, the researchers left the students alone with the radishes and the cookies, and observed them through a small, hidden window. The ones in the radish condition clearly struggled with the temptation.

Some of the test subjects touched or smelled the cookies and chocolate, but none succumbed to the temptation and actually ate the forbidden foods. The second phase of the experiment involved giving the students unsolvable puzzles to work on.

The test was to see how long they’d work before giving up. This has been a standard technique that stress researchers and others have used for decades because it’s a reliable indicator of overall perseverance. (Other research has shown that someone who keeps trying one of these insoluble puzzles will also work longer at tasks that are actually doable.)

The students who’d been allowed to eat chocolate chip cookies and candy typically worked on the puzzles for about twenty minutes, as did a control group of students who were also hungry but hadn’t been offered food of any kind. The sorely tempted radish eaters, though, gave up in just eight minutes—a huge difference by the standards of laboratory experiments. They’d successfully resisted the temptation of the cookies and the chocolates, but the effort left them with less energy to tackle the puzzles.

The hypothesis is that the test subjects in the radish group depleted their willpower by resisting the cookies and chocolate. This left them ill-equipped to handle the self-control needed to work out the puzzles versus the cookie-eaters. The close proximity of those aromatic sweets also probably made the unlucky radish members physically hungry, which would distract them, too. This confounder will come up again, so keep note.

The Mystery of the Dirty Socks

One might assume that highly conscientious people ought to be very orderly in every aspect of their lives. Psychologist Daryl Bem tested this hypothesis in the 1970’s.

He assumed he’d find a positive correlation between “turns in school assignments on time” and “wears clean socks,” because both would stem from the underlying trait of conscientiousness. But when he collected data from students at Stanford, where he taught, he was surprised to find a hefty negative correlation.

“Apparently,” he joked, “the students could either get their homework done or change their socks every day, but not both.”

Further research by Australian psychologists, Megan Oaten and Ken Cheng revealed a familiar pattern.

These psychologists started by administering laboratory self-control tests to the students at different times during the semester. As hypothesized, the students performed relatively badly near the end of the term, apparently because their willpower had been depleted by the strain of studying for exams and turning in assignments. But the deterioration wasn’t limited to arcane laboratory tests. When asked about other aspects of their lives, it became clear that Bem’s dirty-sock finding hadn’t been a fluke. All sorts of good habits were forsaken as the students’ self-control waned during exam period.

The book goes into many more examples than I care to repeat. The take away is that there appears to be a repeatable and predictable loss of willpower levels when a subject is put under stress.

Lessons Learned

The results from these experiments (and others described in the book) can help us understand why humans succumb to temptations.

The experiments consistently demonstrated two lessons:

1. You have a finite amount of willpower that becomes depleted as you use it.
2. You use the same stock of willpower for all manner of tasks.

You might think you have one reservoir of self-control for work, another for dieting, another for exercise, and another for being nice to your family. But the radish experiment showed that two completely unrelated activities—resisting chocolate and working on geometry puzzles—drew on the same source of energy, and this phenomenon has been demonstrated over and over. There are hidden connections among the wildly different things you do all day. You use the same supply of willpower to deal with frustrating traffic, tempting food, annoying colleagues, demanding bosses, pouting children. Resisting dessert at lunch leaves you with less willpower to praise your boss’s awful haircut.

Brain Drain: The Effect of Glucose

We’ve all felt that fatigue of low blood sugar. I used to feel that quite often before I switched to a low carb diet. The inevitable crash that comes after a high starch meal was something I assumed was normal. How does blood sugar affect willpower?

The link between glucose and self-control appeared in studies of people with hypoglycemia, the tendency to have low blood sugar. Researchers noted that hypoglycemics were more likely than the average person to have trouble concentrating and controlling their negative emotions when provoked. Overall, they tended to be more anxious and less happy than average. Hypoglycemia was also reported to be unusually prevalent among criminals and other violent persons, and some creative defense attorneys brought the low-blood-sugar research into court.

Remember the “Twinkie defense?”  But can this condition be tested observationally? Can glucose tolerance be used as a marker to predict self-control?

In one remarkable study, researchers in Finland went into a prison to measure the glucose tolerance of convicts who were about to be released. Then the scientists kept track of which ones went on to commit new crimes. Obviously there are many factors that can influence whether an ex-con goes straight: peer pressure, marriage, employment prospects, drug use. Yet just by looking at the response to the glucose test, the researchers were able to predict with greater than 80 percent accuracy which convicts would go on to commit violent crimes. These men apparently had less self-control because of their impaired glucose tolerance, a condition in which the body has trouble converting food into usable energy. The food gets converted into glucose, but the glucose in the bloodstream doesn’t get absorbed as it circulates. The result is often a surplus of glucose in the bloodstream, which might sound beneficial, but it’s like having plenty of firewood and no matches. The glucose remains there uselessly, rather than being converted into brain and muscle activity. If the excess glucose reaches a sufficiently high level, the condition is labeled diabetes.

Other more control experiments such as giving fasting people diet lemonade vs. sugar sweetened lemonade and then making them play computer games showed distinct negative behavioral differences in the hypoglycemic test subjects.

The Vicious Cycle

The hypoglycemic brain seems to drive the body to crave sweets. It makes sense since that would be the quickest way to get glucose into the system. What about other so-called hyper-palatable attributes like salt and fat? Not so, according to the authors.

As the body uses glucose during self-control, it starts to crave sweet things to eat—which is bad news for people hoping to use their self-control to avoid sweets. When people have more demands for self-control in their daily lives, their hunger for sweets increases. It’s not a simple matter of wanting all food more—they seem to be specifically hungry for sweets. In the lab, students who have just performed a self-control task eat more sweet snacks but not other (salty) snacks. Even just expecting to have to exert self-control seems to make people hungry for sweet foods.

My Alternate Solution

The book has an entire chapter on the paradox of dieting. It goes something like this: “Your brain needs glucose, but glucose causes weight gain. If you deprive the body of glucose, you deplete willpower, which leads to increased glucose ingestion.” The authors seem to view dietary glucose as “brain food” and imply it’s necessary to function optimally.

People who understand how low carbohydrate diets work probably have already found the fatal flaw of this catch-22. A body in a ketogenic state does not have the same limitations on energy availability as one that relies on glucose for fuel. Gone are the wild swings in blood sugar and the craving for sweets. Most organs use ketones for fuel and the liver (and possibly the brain itself) produces whatever minimal amount of glucose is needed to keep blood sugar in check. The authors recognize the benefit of low-glycemic food sources, but may not be aware of the effect from a high fat, very low carbohydrate diet.

Summary

The benefits of low carb diets with regard to hunger vis-à-vis blood sugar and insulin have been well-established. However, other diet research have been focused on the effect of food reward and palatability. The idea that fatty, salty, and sweet foods trigger human reward centers in the brain lead to overeating may contradict the idea that macronutrient ratios are important. Examining the effect of glucose on willpower seems to imply that macronutrients do have a demonstrable effect on human behavior including eating patterns and overfeeding. Furthermore, a low carbohydrate diet (especially a ketogenic diet) may lend itself to sustained levels of willpower in all aspects of life, while a high glycemic, high carbohydrate diet may lead to a positive feedback loop of ever increasing glucose dependency and depletion of self-control.

References and External Links

Baumeister, R. F., Bratslavsky, E., Muraven, M., & Tice, D. M. (1998). Ego Depletion: Is The Active Self A Limited Resource? Journal of Personality and Social Psychology, 74(5), 1252-1265. Retrieved February 10, 2014, from http://dx.doi.org/10.1037//0022-3514.74.5.1252

Oaten, M., & Cheng, K. (2005). Academic Examination Stress Impairs Self-Control. Journal of Social and Clinical Psychology, 24(2), 254-279. Retrieved February 10, 2014, from http://dx.doi.org/10.1521/jscp.24.2.254.62276

Gailliot, M. T., Baumeister, R. F., DeWall, C. N., Maner, J. K., Plant, E. A., Tice, D. M., et al. (2007). Self-control Relies On Glucose As A Limited Energy Source: Willpower Is More Than A Metaphor. Journal of Personality and Social Psychology, 92(2), 325-336. Retrieved February 10, 2014, from http://psycnet.apa.org/journals/psp/92/2/325/

Gailliot, M. T., & Baumeister, R. F. (2007). The Physiology Of Willpower: Linking Blood Glucose To Self-Control. Personality and Social Psychology Review, 11(4), 303-327. Retrieved February 10, 2014, from http://psr.sagepub.com/content/11/4/303.abstract

Epstein, Jim. "Self-Control is the Key to Success: John Tierney and Roy Baumeister on Willpower." Reason.com. N.p., 10 Feb. 2014. Web. 10 Feb. 2014. <http://reason.com/reasontv/2014/02/10/self-control-is-the-key-to-a-success-joh>.

YouTube video from this interview: