The freshly new study published by Cecile Marczinski & Amy Stamates of North Kentucky University shows mixing diet soda with alcohol in your drinks would actually get you 18% more wasted.
The experiment involved 16 participants; those with diet soda had a BrAC (breath alcohol concentration) of over 18% than the participants drinking regular soda with alcohol.
In the study, all participants were given the exact same amount of Vodka (0.03oz per pound of body weight) added to the exact same amount of soda or diet soda.
All participants were tested directly after drinking their glass.
For more information & the complete study - source.