I think it is possible for the server to return content in response to a PUT. If you are using a response envelop format that allows for sideloaded data (such as the format consumed by ember-data), then you can also include other objects that may have been modified via database triggers, etc. (Sideloaded data is explicitly to reduce # of requests, and this seems like a fine place to optimize.)
If I just accept the PUT and have nothing to report back, I use status code 204 with no body. If I have something to report, I use status code 200, and include a body.