Healthier and slimmer adults have better self-control, studies show

PUBLISHED : Tuesday, 25 September, 2012, 12:00am
UPDATED : Tuesday, 25 September, 2012, 10:56am

I will not eat fudge cake. I will not eat fudge cake. I will not eat fudge cake. I will eat fudge cake.

Why is it that some people can resist temptation while others can't? Experts zero in on one factor - self-control - and many believe that this trait is a limited resource.

Self-control enables us to maintain healthy habits, save for a rainy day and get important things done. But according to the model originally proposed by social psychologist Roy Baumeister of Florida State University in the 1990s, if we exercise a lot of self-control by resisting an impulse handbag purchase, we may not have enough self-control later in the day to refuse that slice of fudge cake.

More than 100 research papers have produced findings that support this model. A recent study by the University of Iowa, to be published in next January's
Journal of Consumer Psychology, used MRI brain scans to show the limits of self-control. Study participants were placed in an MRI scanner and made to perform two self-control tasks - first, ignoring words that flashed on a computer screen, and then choosing preferred options.

Subjects had a harder time exerting self-control on the second task, a phenomenon called "regulatory depletion". The brain scans showed that the anterior cingulate cortex - the brain area that recognises a situation in which self-control is needed - fired with equal intensity throughout the two tasks. This suggests the subjects had no problem recognising temptation. But the dorsolateral prefrontal cortex - the brain area that manages self-control - fired with less intensity after prior exertion of self-control. This suggests it got harder and harder not to give in to temptation.

But can self-control really become depleted? Researchers Michael Inzlicht of the University of Toronto and Brandon Schmeichel of Texas A&M University don't think so. In an article published in this month's issue of
Perspectives on Psychological Science, they argue that a newer crop of studies show that self-control may actually be more like a motivation- and attention-driven process.

"Engaging in self-control, by definition, is hard work; it involves deliberation, attention and vigilance," the authors write. They suggest the inability to resist that slice of fudge cake is not necessarily because we're "out" of self-control, but rather because we choose not to control ourselves any longer. At the same time, our attention shifts so that we're less likely to notice cues that signal the need for self-control and pay more attention to reward cues. Fudge cake, as we all know, contains empty calories, but it's also a delectable treat.

Some studies suggest that self-control is linked to genes. A study of more than 800 sets of twins published in May in the
Journal of Personality found that identical twins - whose DNA is exactly the same - were twice as likely to share character traits such as self-control, decision making or sociability, compared with non-identical twins.

But whether it is nature or nurture, exhibiting self-control at a young age is linked with having a lower body mass index as an adult. The study, which tracked subjects for 30 years, was published last month in the
Journal of Pediatrics.

Between 1968 and 1974, 653 four-year-olds completed a delay-of-gratification test, in which they were given one treat, such as a biscuit or marshmallow, and told they would be given a second treat if they could wait to eat the first treat for an unspecified length of time (it ended up being about 15 minutes).

Follow-up studies found that each minute a child delayed gratification predicted a 0.2 decrease in adult body mass index. The preschoolers who could delay gratification for longer also showed adolescent academic strength, social competence, ability to handle stress and higher exam scores.

Research on self-control is important in understanding behaviour related to a wide range of problems, including obesity, impulsive spending, gambling and drug abuse.

If you struggle with self-control, here are some tips to restore your willpower.

Pay more attention to what you're doing A study published this month in the
Journal of Consumer Research made subjects eat either a healthy or an unhealthy snack. Some of the participants were asked to count how many times they swallowed while eating the snack. Those who did so were more satisfied more quickly, even if they otherwise reported poor self-control.

Surround yourself with the right people Self-control - or the lack of it - is contagious, according to a 2010 study by the University of Georgia published in the journal
Personality and Social Psychology Bulletin. The researchers found that watching or even thinking about someone with good self-control made others more likely to exert self-control. The opposite holds true, too.

Postpone consumption Many people find the more they resist unhealthy food, the more they crave it. Nicole Mead, of Catolica-Lisbon School of Business and Economics, suggests postponing consumption to an unspecified future time can reduce the desire for that unhealthy snack. In her study, 105 high school students in the Netherlands were given a bag of potato chips. Participants were given different instructions: they were told to either freely eat the chips, postpone eating the chips, or were instructed not to eat them at all. The others could choose one of the three eating strategies. Over the course of one week, students who initially postponed eating the chips - whether by instruction or not - ate the fewest chips.

Watch your favourite television reruns Two studies in this month's
Social Psychological and Personal Science journal found that watching a favourite rerun may help restore the drive to get things done in people who have used up their reserves of willpower. Watching reruns does not use up mental energy, explains researcher Jaye Derrick, of the University of Buffalo's Research Institute on Addictions. "At the same time, you are enjoying your interaction with the TV show's characters, and this activity restores your energy," she says.

Refuel Willpower, according to Baumeister's research, can be beefed up like an unused muscle. In one study, subjects given a sugar-sweetened drink had improved self-control. Apparently, the sugar provided fuel for the brain to get back to work and restore the person's willpower.

Seek divine intervention In an article in the journal
Psychological Science, psychologist Kevin Rounding of Queen's University, Ontario, ran experiments in which he primed volunteers to think about religious matters. They had more discipline than the control group, and more ability to delay gratification.