D7 RSS Feeds - Omitting Content Fields
You can specify under "Manage Display" how the content you want to feed will look in the "RSS" (or any other) viewmode. By default, you only have the body (or any additional fields) available. To have more control over what's displayed in which viewmode, you can use the Display Suite module. This module allows you (among many other features) to use another layout for this content. By enabling a layout on the viewmode you like, you also get additional fields like for example the Author and the Post date which you then can enable or disable.