For many years my cocktail of choice would be Bacardi and Diet Coke. I figured the diet soda helped me to maintain my weight. Unfortunately a February, 2013 study found that this can increase one's intoxication rate. Here's why.
Part of how the body gets intoxicated depends on the amount of alcohol that hits the brain at once. It makes sense. If you have a full stomach of dense food, and then you sip a beer, it takes a while for that beer to get digested and into your brain. It hits you slowly and you don't get much of an impact. On the other hand, if you have a completely empty stomach and you chug down a beer, that beer hits you hard and you feel the effects strongly.
So take this same thought pattern into a diet soda situation. The study was done at Northern Kentucky University. Some test subjects drank a cocktail of regular soda plus alcohol. Other subjects drank a cocktail of diet soda plus alcohol. In terms of stomach activity, with the sugar-filled drinks, there was something else for the stomach to do. It was digesting those sugars and also handling the alcohol. So the end result had the student with a blood alcohol level under the driving limit. That is, it was legal for them to drive.
However, for the subjects who drank the ZERO sugar cocktail, the stomach had nothing else to do but get that alcohol processed. All the alcohol went right into the blood stream. The result was that those subjects ended up with a blood alcohol level OVER the legal limit.
So the exact same drink volume, the exact same ingestion speed, the exact same body setup. The only difference was sugar vs no sugar. Those with sugar slowed down the alcohol absorption and were legal to drive. Those with no sugar in their drinks spiked their blood alcohol level and became illegal.
Not only were they past the legal driving limit, but the no-sugar subjects were far more impaired in all of their tests.
So the message here is, if you're out without a designated driver, it is safer to have either the sugared soda or food with your drink. Make sure you have something for your body to digest. That will help the alcohol move more slowly into your system, which will protect your brain, your liver, and your overall health.
Lisa Shea's Library of Low Carb Books