Statistics
Statistical Abstract of the United States gives access to statistics collected by the United States Government. The latest statistics available may be from 2006 or 2007, possibly later, with occasional projections for 2010. This information is also available in book format with an index at the Libraries' Reference Desk. Sometimes it's easier to page through a book than second-guess a machine! There is an online index, but be aware that the numbers refer to table numbers, not pages.
There is a section for Health and Nutrition. Some of the tables deal with hunger and some with food consumption (Tables 209-213). You might also find useful information by looking up food, especially food costs.
The Economic Research Service (http://www.ers.usda.gov/Briefing/FoodSecurity/) is a division of the U.S. Department of Agriculture. This link takes you to a page which defines terms like food insecurity and has articles dealing with it rather than to the main page (http://www.ers.usda.gov/) because it is most specific to the topic, but it may be worthwhile to check out the main page. Pay attention to the navigation boxes on the right and left of the main section. This will give you access to more in-depth material, including graphs and statistics, which can be downloaded. Be sure to cite the source.
The World Hunger Organization has a good article explaining hunger and its interrelationships with poverty. It has a bibliography which has citations to reliable journals and other trustworthy websites, like the Food and Agriculture Organization of the United Nations. Its Report on the State of Food Insecurity in the World, 2009, has useful information.