You know the feeling; you skip lunch to complete an important project. But, as the deadline looms, your concentration wanes. You force yourself to keep going, but the end result is less than impressive. Your willpower in skipping lunch has had the opposite effect. Now, researchers are saying that willpower or self-control relies on glucose as an energy source.
Research by Roy Baumeister, a psychology professor at Florida State University, and published in this month’s Current Directions in Psychological Science reveals that:
- Acts of self-control reduce blood glucose levels
- Low levels of blood glucose after an initial self-control task predict poor performance on subsequent self-control tasks
- Initial acts of self-control impair performance on subsequent self-control tasks, but consuming a glucose drink eliminates these impairments.
In one study, participants watched a video, but some were asked to suppress smiles and other facial reactions. After the film, blood glucose levels had dropped among those who had exerted self-control to stifle their reactions, but stayed the same among the film watchers who were free to react.
The video watchers were later given a concentration test in which they were asked to identify the colour in which words were displayed. The video watchers who had stifled their responses did the worst on the test, suggesting that their self-control had already been depleted by the film challenge.
But the researchers also found that restoring glucose levels appears to replenish self-control. Subjects who drank sugar-sweetened lemonade, which raises glucose levels quickly, performed better on self-control tests than those who drank artificially-sweetened beverages, which have no effect on glucose.
The findings make sense because it’s long been known that glucose fuels many brain functions. Having a bite to eat appears to help boost a person’s willpower, and may explain why smokers trying to quit or students trying to focus on studying often turn to food to sustain themselves.
Consuming sugary drinks or snacks isn’t practical advice for a dieter struggling with willpower. However, the research does help explain why dieters who eat several small meals a day appear to do better at sticking to a diet than dieters who skip meals.
Reference
Baumeister, R. F., Vohs, K. D. & Tice, D. M. (2007). The Strength Model of Self-Control. Current Directions in Psychological Science 16, 351–355.
