(CNN) -- Most people choose artificially-sweetened soda over regular soda to avoid packing on extra pounds. But what if you already choose diet? Would it be helpful to quit that too?
Dr. Jim Hill says he gets this question all the time from patients in his weight loss program at the University of Colorado's Anschutz Health and Wellness Center.
With funding from the American Beverage Association, Hill helped design a study that divided approximately 300 adults into two groups: One group would continue drinking diet, and the other group -- referred to in the study as the "water group" -- would go cold turkey. The study was published in the journal Obesity.
Both participant groups received intensive coaching on successful techniques for weight loss, including regular feedback on the meals they logged in journals.
"The results, to us, were not at all surprising," says Hill.
While the typical participant banned from drinking diet sodas lost 9 pounds over 12 weeks, those allowed to continue drinking diet soda lost, on average, 13 pounds in the same time period. That's a 4-pound difference.
Hill says that in his clinical experience, many people who have successfully lost significant weight "are heavy users of noncaloric sweeteners."
But why was the diet soda group more successful? The most likely reason is that this group had the easier task.
Cutting calories and boosting exercise takes a lot of willpower. Trying to simultaneously give up something else you regularly enjoy -- such as diet soda -- taxes your ability to stay the course. Most psychologists agree that our willpower is a limited resource.