In a nation plagued by obesity, where a majority of people seem to be on a diet, it came as a surprise to researchers that more than half of the adults 65 and older who turned up in one emergency room were either malnourished or at risk for malnutrition.

"We were even more surprised that most malnourished patients had never been told they were malnourished," said Dr. Timothy Platts-Mills, an assistant professor of emergency medicine at the University of North Carolina at Chapel Hill.

He's the lead author of a report published in the Annals of Emergency Medicine that showed that 83 of 138 (60 percent) of elderly adults examined in university hospital's emergency room qualified as either malnourished or at risk for malnutrition. Of those, 17 had never before received a diagnosis of malnutrition, even though almost everyone had a primary care physician.

So how, in a nation famous for an abundance of foodstuffs, could so many elderly adults have trouble getting enough to eat? Depression proved to be a big factor. Fifty-two percent of the adults found to be malnourished had symptoms of depression.

Difficulty eating, usually because of tooth pain or denture problems, was found in 38 percent of the cases, while 33 percent reported difficulty affording groceries.

Malnourishment doesn't always make people look emaciated, so how can people with no medical expertise recognize the problem among their own families and friends?

"Pay attention to activity levels," Platts-Mills suggested. "If older adults are continuing to do all their usual activities and enjoying them, then their diet is probably OK. If they are dropping activities, then it's time to start thinking about what might be causing the problem."

Listen for complaints about painful teeth and other dental problems, he added, since that can affect not only nutrition but other aspects of health. And if you suspect an older family member or friend is suffering from malnutrition, make sure that person has access to plenty of healthy food.