Did you know that your sleep habits can make you crave French fries?

Or affect your batting average?

Or hurt your grades?

Apparently, sleep -- or the lack of it -- leaves its mark on us in more ways than we realize, according to scientists at an international sleep conference in Minneapolis this week.

More than 5,000 people gathered Monday to talk about sleep and share more than 1,000 scientific studies at the annual meeting of the American Academy of Sleep Medicine at the Minneapolis Convention Center.

A common theme: our collective struggle to get a good night's sleep.

"It's been overlooked for so long, and [it's] such a major problem," says Dr. David Kuhlmann, a sleep specialist from Sedalia, Mo. It's not just sleepy drivers -- although that's bad enough, he says. "It's [the] impact on overall health."

At Harvard University, for example, researchers found that people are more likely to give in to temptation and eat high-calorie foods when they're sleepy.

"A lot of us kind of knew that [from college]," said William Killgore, an assistant professor of psychology. "You want to eat a little extra carbs to keep going."

But his team discovered that something happens in the brains of sleepy people when they're shown pictures of ice cream, hamburgers and other fatty foods. The "braking system" in the brain, which normally tells them to resist such foods, "starts shutting down," he said. "And the more likely they are to reach out for something to eat."

Over time, he said, that could play a role in the obesity epidemic.

Another study, done at the University of Michigan, compared the grade point averages of 201 college students. No surprise, they found the ones who were sleepiest during the day had the lowest GPAs.

Even professional baseball players came under the microscope. A Virginia scientist studied 16 athletes from seven Major League Baseball teams (not including the Twins). Those who considered themselves "morning types" -- who prefer to go to bed and rise early -- had higher batting averages (.267) than their teammates (.252) in games that started before 2 p.m. But not after.

The study, although small, "clearly shows a trend toward morning-type batters hitting progressively worse as the day becomes later," wrote Dr. W. Christopher Winter, the lead scientist.

Not all the research, though, was so literal-minded. One study, from Paris, was titled "Paraplegics walk in their dreams." The scientists found that sleep, for those who had lost the ability to walk, provided a brief escape from confinement.

One wrote of a dream: "I was in a white tutu and pink ballet shoes," dancing "Swan Lake." Wrote another: "I was not in a wheelchair, but walking to a nightclub to go dancing."

The sleep conference ends Wednesday.

Maura Lerner • 612-673-7384