The dieter's Catch-22: To have willpower, you need to eat

Sweetness and power could have new meanings because of the book Willpower: Rediscovering the Greatest Human Strength. (Read the book's introduction.) In it, research psychologist Roy F. Baumeister explains the links between glucose and self-control, and between willpower and how we might change our lives. His co-author is New York Times science columnist John Tierney.

Lynne Rossetto Kasper: What did your co-author discover?

John Tierney

John Tierney: He discovered that willpower actually is this form of mental energy and that it’s powered by glucose in the bloodstream. This is a store of mental energy that you use and that you deplete when you resist temptations, when you make yourself do something, when you exercise self-control and even when you make decisions. All this depletes the same source of mental energy and it depletes the level of glucose in your blood. 

LRK: You’re saying that sugar is actually feeding my mind?

JT: In some sense, it does. In the laboratory experiments, they love to use sugar. They use lemonade with sugar and the control group takes lemonade with Splenda. The control group can’t tell the difference, but the people who get sugar actually have improved self-control. Our advice is don’t try this at home. Straight sugar is not the greatest way to do it. You get glucose from just about any kind of food, so we advise people to eat healthier foods that will result in a longer, extended release of glucose. Sugar works great in the laboratory because it’s very quick-acting. You go right up and down and you can observe the effects right away, but it’s not so great in your personal life.

LRK: The psychologists say that there are only two predictors of how we’re going to turn out as people: intelligence and self-control.

JT: That’s right. People with stronger willpower do better in school and at work; they’re healthier, they’re wealthier, they’re happier, their personal relationships are better and their children are more likely to thrive. As you say, self-control and intelligence are the two predictors of these things, and it’s a lot easier to improve your willpower than to improve your IQ.

LRK: Wasn’t there a study back in the 1960s with children and marshmallows?

JT: Right. It was an accidental finding that pointed the way toward the importance of self-control. They would put a marshmallow in front of children and then say, "You can have this marshmallow if you want, but if you wait 15 minutes until I come back, I’ll give you another marshmallow." They were really interested in figuring out how children resist temptation. What strategies do they use? The strategy that tended to work was the child looking away from it, not just staring at it. The researcher noticed later that the kids who were able to resist the marshmallow did so much better in school than the ones who couldn’t. That pointed the way toward the importance of self-control and achievement. Since that time, there have been a lot more studies -- much bigger studies. One that just came out in 2011 tracked thousands of children for decades and found that it predicted success in everything: school, jobs, saving money, staying married, saving for retirement, staying out of prison. Self-control predicts so many good things in life. 

But the real implication of this discovery is that willpower is a finite resource you have. It’s like a muscle; you can actually strengthen it through exercise. 

Just sitting up straight will strengthen your willpower over time. But at the same time, it’s like a muscle: It gets fatigued as you use it during the day, so you have to recognize that you just can’t count on it to get you through one crisis after another. If you’re resisting a lot of temptations, or if you’re making a lot of decisions, all those deplete the same resource. 

Roy has also found that people with the best self-control are the people who aren’t exercising willpower all day long. They’re the ones who structure their lives by avoiding the need to do it. They don’t go to all-you-can-eat buffets. They don’t bring junk food home and leave it sitting on the counter. They try to minimize the need for self-control, so when there is an emergency, when they face that tempting dessert cart at a restaurant, they have the willpower to resist it. 

LRK: I’m thinking dieting, because dieting can be about denying yourself food. But you’re saying we have to eat to supply the brain with the glucose to resist eating?

JT: It's a dieter's Catch-22. To not eat, you need willpower. But to have willpower, you need to eat.

People beat themselves up for being overweight, and people tend to equate being able to control your weight with willpower. And there is a connection: People with better willpower and better self-control are better at maintaining their weight. But it’s not nearly the strong connection there is with most other aspects of life -- doing well in school, at work and in relationships -- because the body rebels against this. If you try to starve it, if you don’t give it any glucose, then your willpower declines. And the body fights back when it’s being starved. Willpower will help you avoid temptations, it can help you establish good habits to avoid gaining weight, but it’s not a marker. People who are overweight do not necessarily have weak willpower. It’s the weakest connection they’ve found in this.

LRK: For someone who does want to lose weight, is there one piece of advice that you can offer that will feed the brain and help exercise that willpower?

JT: Set a specific and realistic goal -- maybe 1 pound a week. Also, set a short-term goal for a month or two. Then, monitor your progress. They used to advise people, "Don’t weigh yourself more than once a week because you’ll have these ups and downs and it’ll discourage you." This didn’t really jive with the self-control research, because researchers always found the more you monitored yourself, the better self-control you would have.

They did a big study and they found out that in fact people who weighed themselves every day were the ones who were most able to lose weight. I found out about that while writing the book and I got this scale that sends my weight electronically to my computer and my smartphone. I see the grim news every day. But it did help me lose weight.