By Erin Holaday
Photos by Shaun Ring
After a busy day without a lunch break, how many times have you had that extra piece of chocolate cake, or another glass of wine later that night, when you knew, in your heart of hearts that you might not really need it?
"And the next morning, you're beating yourself up about it," said UK psychology graduate student Holly Miller. "It happens to everyone."
But according to a new study headed up by Miller, it's not necessarily your fault. "Without fuel, you can't inhibit the bad behavior," she explained. "It's physiology."
- Read more about Miller's research in the Huffington Post
- Listen to a Podcast about Miller's research on iTunes
Miller was attending a colloquium at UK last fall, when a presentation by Florida State University social psychologist Roy Baumeister caught her attention.
Baumeister's study involved glucose and self-control. Self-control was defined as doing what you should be doing as opposed to doing what you want. Self-control runs off of energy, which our bodies break down from all foods into glucose.
Using radishes and chocolate chip cookies, Baumeister tested the effects that food restrictions had on energy for self-control. Both food choices were placed in front of study subjects for the experiment, and each participant was allowed to eat one, but not the other.
"When people were forbidden to eat cookies, but permitted to eat radishes, they spent less time attempting to solve brain puzzles afterwards," explained Miller. "When they were permitted to eat cookies, but not radishes, they persisted with their attempts to solve the puzzles for longer."
Baumeister concluded that a resource was depleted throughout the time the subjects had to exert self-control not eating the cookies. In other words, a person’s sense of self was depleted, and as a consequence, people could not work toward their ideal self.
Miller agreed with Baumeister that a resource does indeed fuel the process of self control, but she thought that this depletion and fueling had little to do with a sense of self.
"I thought that it was just a matter of glucose depletion--purely physiological," she said. "They were very skeptical, especially when I wanted to study the depletion effects of glucose in dogs."
Thomas Zentall, a professor of animal learning, behavior, and cognition at UK, had assisted Miller in obtaining a space to run dog subjects on campus three years ago and there were no lack of participants. "We've had tons of support from the Lexington community and the psychology department," she smiled. "We're the best dog-sitters around."
Miller's study yielded astounding results. The canine behavior mirrored that of Baumeister's human experiment.
Trained dogs were told to sit and stay for 10 minutes, while another group was made to sit comfortably in a cage, sitting and staying, but not being told to do so. No self control needed.
Both dogs then had to solve a puzzle following the "sit and stay," similar to Baumeister's study with radishes and cookies.
The caged dogs that hadn't been forced to control themselves in any way worked on the puzzle twice as long as the "sit and stay" group. These were the same basic results that Baumeister obtained.
"A sense of self doesn't really matter here," Miller said. "Dogs don't have a sense of self, or an ideal self, as far as we know. Doing this type of experiment with dogs allows us to explain the results in a less complicated way."
To more clearly test the results of glucose on self control, the dogs were then given either a glucose drink or a placebo (a sweet-tasting drink with no glucose); the dogs worked through the puzzle for a longer period of time with the increased energy.
"My results prove that yes, self control does correspond with diet," said Miller. "There's a reason that you should eat healthy foods that provide longer lasting sources of glucose. Your brain stays strong, and your resistance/self control from unhealthy foods stays high. Foods like carrots and lean proteins take longer to break down, so they provide glucose for a longer period of time."
But, when you do fall off of the wagon, don't despair, counsels Miller. "Breaking down and eating two pieces of chocolate cake has nothing to do with how good of a person you are," said Miller. "It's purely physiological."
Miller has employed this view with her own eating habits. "This made me feel relieved, and it's helped me not beat myself up," she said. "A lot of really determined people can get down on themselves about something like this. The truth is, if you push yourself to the point where you don't have any resources, you can't help it."
"Diets fail more often than they succeed," she continued. "This study is applicable to our daily lives. Diets might fall short, but it's not our fault. We should learn from our failures and adjust our eating habits so that we can fuel our self-control more effectively in the future."