Saving calories at the bar may not be a good thing.

Researchers gave college students vodka drinks with regular soda and with diet soda, and the diet soda group got more intoxicated, faster - about 20% more intoxicated than those who mixed regular soda with liquor, according to research published Tuesday in the journal Alcoholism: Clinical & Experimental Research. Sugar in your mixed drink actually slows down the effects of alcohol, researchers say.

The study

Though it was a very small study, only eight women and eight men, the findings closely match previous research linking diet drinks and increased alcohol levels in the body.

Scientists at Northern Kentucky University asked students who were social drinkers to come to their lab on separate days to test the effects of alcohol. During one visit, the students drank vodka with diet soda and at another session they mixed the vodka with a sugar-sweetened soft drink. Each beverage had the potency of about four mixed drinks, a dose that has been shown to raise blood alcohol levels to about the legal driving limit. At each visit, the students downed their drink in about 10 minutes.

The results

Using breath tests to measure alcohol levels, researchers found that students who drank vodka and regular soda registered just under the legal limit. But drinking the vodka-diet soda mixture tipped students over the limit.

"What you choose to mix your alcohol with could possibly be the difference between breaking or not breaking the law," says study author Cecile Marczinski, assistant professor in the Department of Psychological Science at Northern Kentucky University in Highland Heights, Kentucky.

The students also completed computer tasks testing their reaction times, mimicking what they might face while driving. Those drinking the diet soda were slower to react.

But the students said they felt the same no matter what they drank, even though tests showed the diet drinkers were about one-fifth more intoxicated. To put that in perspective, you'd have to add almost a whole other shot of vodka to the sugar-sweetened drink to equal the potency of the diet drink mixture.

"The subjects were unaware of this difference, as measured by various subjective ratings including feelings of intoxication, impairment, and willingness to drive," says Marczinski.

Another study measuring alcohol levels in people leaving bars or night clubs also found that diet soda/liquor drinkers were more impaired.

"Marczinski's findings are very consistent with what we've found in the field in a natural drinking environment. When the mixer is diet soda, the bar patrons tend to have somewhat higher intoxication levels than when they consume regular soda," says Dennis Thombs, professor and chair of the Department of Behavioral and Community Health, School of Public Health at the University of North Texas in Fort Worth.

People often mix diet soda and alcohol to save on calories. And women make this choice more than men. But Marczinski says it's not worth the trade-offs."It's much more harmful to the brain, to your liver, if you have a higher blood alcohol level. A few extra calories is not going to make that much difference (in your weight)," says Marczinski. In her study, students drinking the diet mixture only reduced their calorie count by 130.

What's the buzz?

Why do people get more intoxicated when they go for diet instead of regular soda with their booze? It has to do with digestion. The diet soda mixture passes quickly through the stomach, putting alcohol into our bloodstream faster.

That's not the case with regular soda and liquor. Experts say the stomach treats this combination as if it's food. Digestion slows everything down, delaying the release of alcohol into our system, and spreading it out over a longer period of time.

Take home

"I think the takeaway from this study is, don't trust your judgment about intoxication levels, you may be off," says Marczinski. "And many times people think they're safe to drive and they are in fact not."