Part of the problem may be traced back to aspartame, the artificial sweetener used in many diet sodas. According to a study from other researchers at the university, heavy exposure to aspartame may directly increase blood glucose levels, leading to an increase in diabetes risk. "Artificial sweeteners could have the effect of triggering appetite but unlike regular sugars they don't deliver something that will squelch the appetite," explained Sharon Fowler, an obesity researcher who co-authored both studies, in an interview with the Daily Mail.