Psychology research elucidates dieting behavior

by Chris Leech | 11/17/13 6:02pm

Dieters’ ability to self-regulate is severely diminished after a long, stressful day — and the food they aim to avoid looks tastier too, according to a new study by psychology professor Todd Heatherton.

Past behavioral studies have shown that self-control becomes depleted over time. Using functional magnetic resonance imaging, Heatherton’s team reaffirmed this theory and found that temptations become even more appealing to an overworked individual.

“The theory is that humans have a core resource or strength that allows them to self-regulate, but that this resource can be fatigued or depleted,” Heatherton said. “The best analogy is a muscle — you could have a strong muscle, but it can still be overtaxed, and at some point it, will give out.”

Becca Boswell ’10, a co-author of the research who is pursuing a PhD in clinical psychology at Yale University, described self-control as a see-saw between cognitive control and reward value.

“It’s as if, when you’re resisting temptation, the piece of chocolate cake you’ve been trying not to eat suddenly looks like the best cake you’ve ever seen,” Boswell said in an email. Exercising self-control in ways other than dieting can lead to this change. Studying all day, for example, can make it harder for students to avoid overeating, drinking or smoking at night, Boswell said.

To test the hypothesis, researchers scanned the brains of 31 chronic dieters while showing them pictures of craving-inducing food. Half of the dieters had previously completed a task requiring self-control. When shown the pictures, this group of dieters’ brains exhibited more activity in orbitofrontal cortex -— the region of the brain that evaluates the appeal of food — than those in the other group. The fMRI scans also showed fewer connections between orbitofrontal cortex and a separate area of the brain associated with self-control and restraint.

The research, on a practical level, shows that if a dieter has to exercise self-control throughout a day, such as by waking up for class or staying off Facebook, the next time the dieter experiences a craving, he or she is more likely to give in. Instead of attempting to resist cravings, the research suggests that these people should avoid temptations entirely.

“I think this paper comes out at a good time. For quite awhile there was the tacit belief that when people’s self-regulatory capacity is exhausted, the lure of temptations, such as appetizing food, doesn’t really change,” lead author Dylan Wagner ’10 said in an email. “Our work adds another piece to the puzzle.”

The research has implications beyond the average late-night Collis binge. Heatherton hopes that, as students understand the self-control depletion that takes place during a school day, they can recognize when they are vulnerable to making poor decisions about food, alcohol and sex. People are most likely to fall prey to temptations at night, the research suggests.

“Students have to engage in a lot of self-control during the day — just paying attention during a lecture, for example,” Heatherton said.

There may however be ways to replenish one’s ability to self-regulate, such as taking a walk or going on a run. These activities could make an individual stronger in the face of bad impulses.

“If you know you’ve had a really stressful, hard day, keep in mind that maybe you need an hour where you’re just relaxing and where you don’t have to think a lot,” Heatherton said.

Heatherton’s lab, which received grants from the National Institute on Drug Abuse, the National Heart, Lung and Blood Institute and the National Institute on Alcohol Abuse and Alcoholism, studies problems such as smoking and illicit drug addictions, alcoholism and commitment to exercise regimes.

The article, “Self-Regulatory Depletion Enhances Neural Responses to Rewards and Impairs Top-Down Control,” was published in the November issue of the medical journal Psychological Science.