Think of the wings as the glass and the fuselage as the tea in the glass. The pilot's glass of tea is imitating what the wings and fuselage that contain the glass are doing.
If the pilot turns the plane at the correct rate, it's a 1 G maneuver. If he turns a little too fast (like spinning your arm too fast) the downward acceleration relative to the fuselage becomes greater than 1 G. If he turns too slowly, the downward acceleration is less than 1G and the tea might spill.
I use the term downward acceleration because "G Force" is not a term that physicists like to use.
If the pilot turns the plane at the correct rate, it's a 1 G maneuver. If he turns a little too fast (like spinning your arm too fast) the downward acceleration relative to the fuselage becomes greater than 1 G. If he turns too slowly, the downward acceleration is less than 1G and the tea might spill.
I use the term downward acceleration because "G Force" is not a term that physicists like to use.