Bad spark plugs can be a cause of a lean engine condition with the fuel and ignition system.
The engine needs the proper amount of spark to ignite the fuel properly and when the spark plugs are worn down or fouling out then the spark plugs cannot produce the proper amount of spark to ignite the fuel.
So then a lean condition occurs as a result of the bad spark plugs.
Other causes of a lean engine condition are bad fuel pump, low fuel fuel pressure, dirty fuel injectors, bad ignition coil, bad spark plug wires or even low engine compression.
If your engine is having a lean condition then you should take it to a mechanic and have them put a testing computer on the vehicle to diagnose exactly what is causing the lean condition.
Even Autozone or Oreilly Auto Parts can check your engines computer for codes if your check engine light is on and then they can tell you what is going on with the vehicle.