Florida State University : Research in Review

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Sweating Sweets
Sweating Sweets

Resisting that piece of double fudge chocolate cake takes a lot of energy. And when the platter comes around a second time, you may find that your strength to hold off temptation is gone. Despite your best intentions, the cake winds up on your plate—and eventually your hips.

Could it be that the very act of exerting self-control can zap your energy? A number of recent studies suggest exactly that—self-control taps into the body's energy supply, and often to surprising degrees.

Most recently, a study at FSU has added to the mounting evidence that the phenomenon reflects a solid physiological reality.

Since 2004, psychology professor Roy Baumeister and his graduate student Matthew Gailliot conducted a series of experiments to trace the connection between self-control and glucose, one of the body's chief sources of energy.

In one experiment, the researchers had subjects watch a six-minute silent video of a woman talking while a series of words appeared at the bottom of the screen. Some participants were told to focus only on the woman's face and to avoid looking at the words. A control group watched the video without instructions.

Blood glucose measurements before and after the task showed that glucose levels dropped significantly for those who tried to focus on the woman's face rather than read the words on the screen.

In another round of experiments, the researchers added to the video test a second self-control task involving the Stroop test, often used in psych labs to measure self-control. A person is shown a series of color names printed in ink of a color different from the color named—for example, the word "red" printed in blue ink. The person must exert self-control to say "red" rather than "blue," the color of the ink.

Subjects who exerted self-control while watching the video showed, as before, lower glucose levels, and then performed poorly on the Stroop test. This result suggested that the first task used up a lot of glucose so there wasn't much left for the second task, resulting in poorer performance.

In a final experiment, the researchers found that consuming a sugary drink between the two self-control tasks restored participants' ability to perform the Stroop test, whereas drinking a Splenda-sweetened beverage did not boost self-control.

So, Baumeister and Gailliot concluded, self-control relies on glucose, an actual, finite energy source.

Does that mean we should eat more sugar to improve our willpower? No, the researchers say.

"We do not intend to advocate consuming large quantities of sugar as an ideal strategy for improving self-control," they write in an article published in the February issue of the Journal of Personality and Social Psychology. "Eating several candy bars, for instance, might give one a boost of energy and better self-control, but these benefits are likely to disappear when glucose levels eventually drop."

So just back slowly away from that chocolate cake, and your body will thank you. —D.W.