first of all to say that I work in Italy
In here we are doing quite a lot of flights so short (probably more in the 500km range than in the shorter ones).
as you can imagine most of the fuel is burnt for takeoff so despite the distance a 737 would need just over a ton just to reach a "low" (eg. 27000') cruising level.
Personally I am flying a Turin-Rome FCO sector every day and the typical fuel burn for a sector like this is 2400KG. (probably up to 2600 if full in a no wind condition)
Alitalia is flying sometimes these routes with A321 which is about the same size of a 757 but no clou on how much they burn.
Hope to be of help.