Would inverting airplane front end increase lift and save fuel?

no

the fuselage of an aircraft is designed to create lift in the same way the wings do, but obviously it cant create as much lift.

Think about it, imagine two particles of air hit the nose of a plane at the same time, one particle goes up over the top and the other goes down underneath.
The particle that goes over the top has a greater distance to travel before it gets to the tail (because of the shape) than the particle that travels underneath.
the upper particle must then increase its speed (because of the laws of conservation, it must get out of the way of the particles coming after it) and will travel faster than the particle under the fuselage.

basic fluid mechanics will tell you that as velocity increases pressure decreases, so the result is a higher pressure below the plane than above it. so the high pressure below pushes the plane up. This is lift.

you could make the entire body a wing, ie, the flying wind. That has been done in military aircraft, see the reference. But there are a lot of problems.

wikipedia:
A clean flying wing is theoretically the most aerodynamically efficient (lowest drag) design configuration for a fixed wing aircraft. It also offers high structural efficiency for a given wing depth, leading to light weight and high fuel efficiency.

Because it lacks conventional stabilising surfaces or the associated control surfaces, in its purest form the flying wing suffers from the inherent disadvantages of being unstable and difficult to control. These compromises are difficult to reconcile, and efforts to do so can reduce or even negate the expected advantages of the flying wing design, such as reductions in weight and drag. Moreover, solutions may produce a final design that is still too unsafe for certain uses, such as commercial aviation.

Further difficulties arise from the problem of fitting the pilot, engines, flight equipment and payload all within the depth of the wing section. A wing that is made deep enough to contain all these elements will have an increased frontal area, when compared to a conventional wing and fuselage, which in turn results in higher drag and thus slower speed than a conventional design. Typically the solution adopted in this case is to keep the wing reasonably thin, and the aircraft is then fitted with an assortment of blisters, pods, nacelles, fins and so forth to accommodate all the needs of a practical aircraft.

Other known problems with the flying wing design relate to pitch and yaw.

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