(CNN) -- The number of Americans fighting off hunger stayed level last year, though food insecurity rates remain the highest they have been since the federal government began keeping track 15 years ago, a Department of Agriculture report released Monday found.

About 14.7 percent of U.S. households were "food insecure" in 2009, meaning they had difficulty feeding one or more of their members at some point last year due to a lack of financial resources, according to the report.

That equates to 17.4 million households total, or roughly 45 million people.

This year's rate marked a slight increase in percentage from 2008, when 14.6 percent of American households had trouble putting food on the table.

The situation was especially dire for more than one-third of those households -- 6.8 million total, equating to 5.7 percent of all U.S. households -- that the report's four authors classified as having "very low food security."

This number, too, changed little in 2009 compared to the previous year.

A lack of resources prompted one or more members of these households to eat much less or otherwise adjust their eating patterns.

The typical household in this category struggled with food issues for at least a few days a month over seven months of the year, the report said.

Households headed by single parents were more likely to struggle with food insecurity than those with two parents at home.

Hunger-related issues were more prevalent among African-American and Hispanic households than white ones, the study found.

Access to food was also more common in large cities than in rural areas, exurbs or suburbs.

Most of those classified as "food insecure" reported getting benefits from the federal government's three main anti-hunger initiatives: the Supplemental Nutrition Assistance Program, the National School Lunch Program and the Special Supplemental Nutrition Program for Women, Infants and Children, better known as WIC.

In a press release, the U.S. Department of Agriculture reported that 18.7 percent more people had participated in the former program in 2009 over 2008. Rates also rose for the "free lunch" program (up 5.4 percent) and WIC (up 5.8 percent).

"This report highlights just how critical federal nutrition assistance programs are for American families," USDA Under Secretary for Food, Nutrition and Consumer Services Kevin Concannon said in a statement.

The annual report from the Economic Research Service extrapolated from surveys of 46,000 households conducted on the Department of Agriculture's behalf by the U.S. Census Bureau. People responded to questions such as their ability to afford balanced meals, whether they adjusted the size of meals due to lack of money, or if they ever went hungry due to a lack of financial resources.