Credit: Terry Doyle

Terry DoyleWondering why one margarita makes you loopy while your friends can go back for seconds (or vice versa)? These factors might just explain it.

Your gender
Adding insult to injury: In women, the enzyme aldehyde dehydrogenase (ALDH)—which breaks down alcohol in the stomach—can work less efficiently than in men, says Scott Walters, PhD, associate professor at the University of Texas School of Public Health. "One drink will get you drunk faster and take you longer to process out of your system than it would a man," Walters says.

Your slim shape
If youve ever been called a "lightweight," its for good reason: The smaller and lighter you are, the fewer drinks it takes to get you drunk. Period. "There are fewer places for the alcohol to go," Walters says. "Anything that isnt diluted in the water in your body will cluster around your organs and take longer to process out of your system."

How much youve eaten
The less food in your stomach before you drink, the faster alcohol is absorbed into your bloodstream, says Sam Zakhari, PhD, director of the Division of Metabolism and Health Effects for the National Institute on Alcohol Abuse and Alcoholism (NIAAA).

So have a salad beforehand (any food works, not just greasy, fatty fare) or order pasta with your wine at dinner. Just dont drink first and eat second, Zakhari adds. "By the time you eat, the alcohol will have already passed from your stomach to your bloodstream, and youll already be buzzed."

When you last exercised
No, working out doesnt change how you metabolize booze—but it does release endorphins, which can decrease appetite, possibly stopping you from eating before you drink. "With no food to absorb it, more alcohol rushes into your system," says Harold Urschel, MD, author of Healing the Addicted Brain and chief medical strategist at Enterhealth Ranch substance-abuse center in Dallas.

What youre drinking
Champagne gets you drunk at a faster rate than other alcohol, likely due to the carbonation, according to a study from the University of Surrey in the United Kingdom.

"The gas bubbles irritate the walls of the stomach, stimulating the blood vessels to dilate and absorb more alcohol," Zakhari says. Mixing booze with soda will also bring on a faster buzz, he says.

How much sleep youve gotten
If youre tired, drinking just a few sips could affect your coordination. "Alcohol lowers your inhibitions," Walters says. "Usually the body compensates by being extra-alert, but if youre tired, it wont be able to stay focused." Your reflexes will be off, and youll be more accident-prone.