I concur with Andy, but in a few more words:
The fuselage of an aircraft provides no lift (or it does so very inefficiently in lifting-body designs), therefore it only contributes to weight and drag. It's a necessary evil in most practical aircraft because the basic idea is to move people or things with the airframe, so a compromise is reached between cargo volume and acceptable fuselage drag. If you instead remove the fuselage, leaving just the wing, you reduce weight (so less lift is required) and drag (so less thrust is required, which allows smaller engines which are also a contributor to airflow inefficiencies).
This is the mentality behind Northrop's various "flying wings" (YB-35, XB-49, B-2) as well as NASA's Pathfinder-style aircraft including Centurion and Helios, and certain other designs such as White Knight (the mother ship for SpaceShipOne; it is technically a twin-boom fuselage design not unlike the P-38, but it was intended to minimize fuselage surface area).