The National Institute of Diabetes and Digestive and Kidney Diseases has published a guide called "Young at Heart: Tips for Older Adults". This guide gives useful information about healthy eating and exercise. This nutrition information can help you to lower your risk for obesity, type 2 diabetes, coronary heart disease, cancer, and other chronic diseases. In addition, exercise may also help to ward off depression. You can access the full report here.
Young at Heart: Tips for Older Adults
You can find even more in-depth dietary guidelines in "Dietary Guidelines for Americans 2010", from the U.S. Department of Agriculture and the U.S. Department of Health and Human Services.