Is it possible to audit changes on List fields in SharePoint 2013? What I'm looking for is to get some report when certain fields in a List is changed by users, not looking for values but just a report on which of the fields were changed?
There are certain classes defined inside Microsoft.SharePoint namespace which you can use to customize your audit report.
Please look into this URL.It actually tells you about auditing and different levels of auditing in Sharepoint.
Without Server Coding
We can use audit feature of Microsoft SharePoint Server 2013 or SharePoint Online to track which users have taken what actions on the sites, content types, lists, libraries, list items, and library files within your site collections
So in List,Libraries and Sites category you can check the event "Editing Content types and columns to get the columns that have been modified or edited by user"
The audit log captures the following information for the events that are selected to be audited.
Site from which an event originated
Item ID, type, name, and location
User ID associated with the event
Event type, date, time, and source
Action taken on the item
To view Audit log reports