I want to get my truck lifted but would it be less fuel economic(apart from the fact that it would be a bit heavier) like would the structure make it less fuel efficient?
yes it will, but to what extent depends on the lift size and tires you chose. best thing is to make sure you re gear the truck for the bigger tires.
The weight will hurt slightly and changing the aerodynamics will also like make it slightly worse but by far the biggest hit will be from the larger tires which is the reason most people do a lift in the first place. Larger tires are more weight and usually softer which causes more drag. They also change your drive ratio. The engine will be turning slower at a give speed than it did stock. This MAY be ok on the highway but will most likely hurt because you will not be running the engine in its optimum rpm for power and at the same time are asking it to do more work so the most likely result is worse MPG.
If you get bigger tires it most definitely will
