The wing on the Skyvan, and its longer derivatives, sat/sits on top of the fuselage. The fuel was/is stored in that part of the wing.
As this section went across the top of the fuselage, its upper side retained the aerofoil shape of the rest of the wing.
So to an extent that would have generated some lift, I guess. Whether that section counts as wing or fuselage is a matter of semantics, in my unscientific view. But this feature is why people talk about a "lifting fuselage", I think.
Any benefit would have been outweighed (if you'll forgive the rather loose use of that term in this context) by the shape of the rest of the aircraft.
As previously remarked, the Skyvan flew due to being repelled by the Earth.
None the less, it had a better STOL take-off performance, with a higher payload, than a Twin Otter. Not a lot of people know that.