A study of 9514 middle-aged Americans from the University of Minnesota showed that those that drank diet sodas regularly were at high risk for developing diabetes in later life (Circulation, February 2008). How can this be? Diet drinks do not contain sugar, and it is a high rise in blood sugar after meals that markedly increases a person's chances of developing diabetes. But who is most likely to drink diet sodas? A person who is overweight and trying to lose weight. So the study does not show that diet sodas cause diabetes. It shows that people who try the hardest to lose weight (and often fail) are the ones most likely to drink diet soda.
However, researchers at Purdue University showed that mice fed artificial sweeteners ate more and put on weight. They believe that a sweet taste causes the brain to seek out more food (Behavioral Neuroscience, February, 2008). The authors propose that: "a sweet taste in the mouth helps prime the metabolism for the arrival of a calorie-heavy, sweet meal into the digestive system." This study needs to be repeated with humans to see if the sweet taste from artificial sweeteners actually causes people to eat more. Weekly newsletter
I've heard about this before. It's also believed that our body reacts to the taste of sweetness. This is because we normally eat sugar before we switch to sweeteners and the body anticipates that we are still eating it and releases insulin to deal with it.
It would be great if they did a study so we could get a definitive answer.