WASHINGTON -- A high-fat diet, at least for a few days, could enhance mental performance, according to a study unveiled Tuesday.

"Nutritional Effects on Cognitive Performance" examined how various diets affected 45 pilots. After four days, pilots on both high-fat and high-carbohydrate diets performed significantly better than those on a high-protein diet.

Results of the study were briefed this week at the Military Health Research Forum in Kansas City, a scientific gathering hosted by the Department of Defense Congressionally Directed Medical Research Programs. A number of the 500 researchers in attendance from the military, industry and academia were surprised at the results.

"We were surprised too," said Dr. Glenda Lindseth, the study's lead researcher, during an interview Wednesday. "It wasn't what we anticipated."

Lindseth admitted that some of her colleagues were even "a little bit troubled" by the findings.

Researchers on her team at the John D. Odegard School of Aerospace Sciences - part of the University of North Dakota at Grand Forks -- at first had trouble believing the results, Lindseth said. "We reran our statistics many times," she said. "We kept analyzing our data as we went along."

But there was no mistaking the outcome.

Pilots on the high-fat diet scored about 50 percent better than those on the high-protein diet. They also scored about 20 percent better than pilots on the "control" or well-balanced diet.

After four days to a week on a particular diet, pilots were tested on a full-motion flight simulator. Their short-term memory was also tested by the Sternberg Item Recognition Test and their spatial orientation was evaluated by the Vandenberg Mental Rotation Test.

After the tests, participants were then randomly rotated into one of the other three diets. After four days to a week, they were tested again.

Pilots on the high-carbohydrate diet also scored more than 40 percent higher than those on the high-protein diet. They had better reaction times and improved memory.

In addition, pilots on the high-protein diet experienced irritability and high anxiety levels, Lindseth said. And they were not able to sleep as well as the other pilots.

Lindseth pointed out that all of the diets were actually balanced as far as the minimum daily required amount of nutrients and about the same amount of calories. However, the high-fat diet consisted of about 57 percent fatty foods, including whole milk, mashed potatoes and gravy, roast beef, and extra sausage patties.

The high-protein diet was comparable to the Atkins diet, Lindseth said, in that it consisted of more than 50 percent protein. Instead of roast beef and gravy, pilots on the high-protein diet might eat a spinach salad with chicken breast.

The latter kind of dinner has long been intuitively considered by many as healthy, and Lindseth cautioned that the long-term results of fatty or high-carbohydrate diets need to be studied further.

"One of the things you want to do with a study like this is take the results cautiously," Lindseth said.

She's not recommending that people take up a high-fat diet for the long run to improve their mental capacity. But she suggests that eating a candy bar or two before a test or a military operation "may not be as bad" as what nutritionists previously thought.

"Maybe people just need to eat (fatty) foods more when they're going to go into a situation when they're going to need to think more clearly or alertly," Lindseth said.

All of the participants in the study were fixed-wing pilots, and a few were military, Lindseth said, including a few pilots from the North Dakota National Guard.

Lindseth suggested that results of the study might be useful to the military far beyond just the field of aviation.

The last slide in her presentation on Tuesday read: "Since peak performance is critical to the warfighter, the effects of diet can have far-reaching consequences in the combat environment."