And, researchers found, fasters ended up eating extra of whatever foods they chose to chow down on first at that meal.

The findings carry a message for anyone who goes for long spans of time without eating, researchers said. That includes patients fasting before a procedure or blood test, some dieters and medical interns working long shifts without a snack break, for example.

"I think this really pushes the importance of what (food) options you have in your environment," said Aner Tal, one of the study's authors from the Cornell Food and Brand Lab in Ithaca, New York.

Tal told Reuters Health that if he knew he wouldn't be able to eat for long periods, he would pay extra attention to what types of food he kept at home.

"It would be important to not overstock on unhealthy options," he said.

For the study, published as a letter in the Archives of Internal Medicine, Tal and his colleagues recruited 128 students from Cornell University.

The students were randomly assigned to one of two groups. One group was told not to eat or drink anything after 6 p.m. the day before the lunchtime study. The other group, which acted as a comparison, was able to eat normally.

By the time students sat down for lunch on the test day, the fasting group had not had anything to eat for about 18 hours.

Each student was offered a buffet lunch of dinner rolls, French fries, chicken, cheese, carrots and green beans, while under video surveillance.

Using the video logs, the researchers recorded which foods the students ate off their plates first. They also measured how much students ate by embedding scales in the lunch table.

Forty-three of the original students didn't follow their assignment and so weren't included in the main analysis.

Of the remaining 40 fasters, 30 first went for the dinner rolls, French fries, chicken or cheese, compared to 20 of 45 students in the comparison group.

Participants ended up eating almost 47 percent more calories of their first-choice food compared to other menu items.

The study cannot say why some students went for the starches and proteins first, but Tal told Reuters Health it may have something to do with an internal drive to seek high-fat foods after a period of deprivation.

PRACTICAL APPLICATIONS

The researchers suggest hospitals and cafeterias who serve people going long periods of time without food should consider these findings and make vegetables and other healthy foods "more convenient, visible, and enticing."

That, they say, may encourage people to pick healthier foods if they haven't had a chance to eat for several hours.

In a commentary published with the study, two nutrition researchers suggest the findings may apply to settings outside of hospitals and cafeterias.

They say this type of research is important for people who are experiencing hunger and food insecurity.

"I think we're just starting to understand some of these factors with obesity, food insecurity and related factors as things that interrelate. I think it will be a missed opportunity if we don't (look into this)," said Amy Yaroch, one of the commentary's authors and the director of the Gretchen Swanson Center for Nutrition in Omaha, Nebraska.

SOURCES: bit.ly/OxDprH and bit.ly/L2edZ4 Archives of Internal Medicine, online June 25, 2012.

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