The benefits of carbs (glucose), the brain's critical fuel source, in tests like word recall, maze learning, arithmetic, short-term memory, rapid information processing and reasoning are well documented. All types of people – young people, university students, people with diabetes, healthy elderly people and those with Alzheimer’s disease – have shown an improvement in what's called cognitive function after eating glucose or a carb meal.
Willpower seems to be affected by our glucose supplies too according to Matthew Gailliot and researchers from Florida State University, which is possibly why being strong minded about one thing can lead to backsliding in another and helps explain why after firmly saying no to an impulse purchase you can find yourself eating a whole chocolate bar! Apparently even relatively small acts of self control deplete the brain's available supply of glucose which then reduces our capacity for exercising further self control until we have topped up the glucose tank. The Florida study involved numerous tests but a key one found that people who drank a glass of regular lemonade between one task requiring self control before beginning a second also requiring a fair bit of willpower performed equally well on both tasks, while people who drank a sugarless diet lemonade in between made more errors on the second task than on the first.
Writing in the Journal of Personality and Social Psychology the researchers draw the conclusion: ‘… the body’s variable ability to mobilize glucose may be an important determinant of people’s capacity to live up to their ideals, pursue their goals and realize their virtues.’ They also point out that they used sugar in their studies because it is fast acting and convenient, but that ‘complex carbohydrates may be more effective for sustained self control.’ Research in memory tests has certainly shown that low GI carbs enhance learning and memory more than high GI carbs, probably because there is no rebound fall in blood glucose.
And there's more. According to Sandra Aamodt and Sam Wang, willpower grows with practice. ‘People who stick to an exercise program for two months report reducing their impulsive spending, junk food intake, alcohol use and smoking. They also study more, watch less TV and do more housework,’ they write.
– Journal of Personality and Social Psychology (2007, Vol. 92. No 2.)
– Sandra Aamodt PhD and Sam Wang PhD are authors of Welcome to Your Brain: Why you lose your car keys but never forget how to drive and other puzzles of everyday life.