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Multi-tasking can make you fat


Juggling too many unrelated tasks can sabotage self-discipline in other areas of your life. As a result, you may find it harder to control your temper, resist fattening foods, or stick to your exercise routine, suggests a new study published in Organizational Behavior and Human Decision Processes. Chalk it up to mental overload, brought on by brain drain from excessive multi-tasking at home or on the job.

Compulsively checking your Blackberry as you help your kids do their homework, or frequently shifting between different tasks on the job can exhaust the “executive function” of the brain. The researchers, a team of marketing professors from Emory’s Goizueta Business School and other universities, have concluded that our brains are only wired to shift mental gears a limited number of times before the intellectual resources required for self control are exhausted, leaving people more prone to such behavior as emotional outbursts or cheating on their diet. The study involved five experiments with about 300 participants who were asked to complete various tasks, using different methods, as their self-control was measured. Here’s a closer look at the study findings:

How does multi-tasking undermine healthy eating? In one experiment, the volunteers were asked to think abstractly about one topic, think in more concrete or technical terms about another, or combine the two types of thought. Afterwards, the volunteers were offered a bitter-flavored beverage and told of its health benefits. Those who switched back and forth between concrete and abstract thought drank one-third the amount of the bitter beverage than did volunteers who were only asked to use one type of thought, thus demonstrating less self-control in healthy eating than did non-multi-taskers, the study found. This finding could also apply to sticking to a weight-loss diet, which requires daily self-discipline, the researchers point out. Also, multi-tasking could make you more prey to the temptations of distracted eating, a common problem when people are stressed out by an overly hectic, juggling lifestyle.

What’s the effect of multi-tasking on physical fitness? In another experiment, a group of bilingual volunteers were either asked to answer questions in one language or switch between two languages. The participants were then asked to perform a physical task: squeezing a handgrip as long as possible. People who answered questions in one language were able to endure for twice as long, suggesting that they had much greater self-control to tough it out on a physical level because their brains weren’t exhausted by the demands of thinking in two different languages. Physical endurance and sustained mental motivation are both key elements for sticking to a workout routine, noted researcher Ryan Hamilton of Emory University.

What’s the effect on mental focus? A third experiment involved playing a game in which volunteers were asked to evaluate geometrical shapes. One group received points for right answers, while another group was penalized for wrong answers. A third group had to repeatedly switch between the two scoring methods as a form of multi-tasking. Afterwards, all of the volunteers worked on a mathematic puzzle that had no solution. The volunteers who had to contend with different scoring systems in the previous task, thus requiring them to shift mental gears, became discouraged and gave up on the puzzle after just five minutes, while the other groups attempted to solve the puzzle for an average of ten minutes before quitting. This suggests that multi-tasking undermines both persistence and concentration, which require mental self-control.

What are the practical implications of this research? It’s smart to focus on one task at a time, instead of shifting back and forth between activities, says Kathleen Vohs, another of the study's authors, because it conserves “mental energy to do the tough stuff,” such as staying motivated to stick your diet and work out regularly, despite the many frustrations, temptations, and obstacles that make sustaining a healthy lifestyle over the long haul so daunting. And from a business perspective, the researchers note, self-control and single-minded focus, even in the face of the tedious tasks and myriad distractions that pop up during the workday, can boost your job performance. The bottom line on multi-tasking? Reducing the frequency with which you jump from one activity to another can help make you healthier, wealthier, and slimmer.

By Lisa Collier Cool

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