The department said in a report on Wednesday that the number of poor Americans who repeatedly ran short of food increased by 800,000 in 2011, Reuters reported.
The report added that women living alone and African-American households suffered the biggest increase in very low food security.
The US government said on Tuesday that a record number of 46.7 million people were enrolled for food stamps in June, showing a 173,000-increase compared with May.
Official figures showed a 3.3-percent hike in participation in the public aid program compared to last year.
According to almost everyone who experienced very low food security, the poor people did not have the money to buy food.
Some 97 percent of poor people said they cut back on the amount they ate or skipped a meal, while 91 percent said it happened often throughout the year.
The food crisis in the US is one of the controversial issues during the presidential election campaign.