NodeJS + Mongoose: Updating all fields on a Mongoose model

I'm building out an api using Node, MongoDB and Mongoose. One thing that is bugging me is that you can't seem to set multiple fields at once:

app.put('/record/:id', function(req, res) {
  Record.findById(req.params.id, function(err, doc) {
    if (!err) {
      doc.update(req.params);
      doc.save();
...

However, it seems that you have to work out the update query and run it on the Model object rather than on the document object. Unless you want to assign individual properties and run save() at the end.

Is there any way of accomplishing this without having to write a Mongo query?