If you like sweet mixed drinks, you may want to order regular instead of diet soda the next time you’re at a bar or party.  A new study finds that drinking diet may be good for your waistline, but it may leave you more impaired.

Researchers had 16 college students and young adults drink vodka with regular soda at a strength equivalent to four mixed drinks.  They took a breathalyzer test and passed.

On a different day, the students drank the same amount of vodka mixed with diet soda.  This time they failed the breathalyzer test.  They were above the legal limit but didn’t know it.

“There’s no sugar in the diet drink so it goes through the stomach a lot faster. The diet mixture kinda fast forwards the digestion process of sending the alcohol into the bloodstream,” says Cecile Marczinski with Northern Kentucky University.  “Higher blood alcohol concentrations they affect your brain, they affect your liver.”