Whilst in level flight you weigh 1 G, as does the whole aircraft. Pulling up and opening the throttle to maintain the speed will cause the whole mass to go up and around. Inertia will now cause the whole aircraft and you within it to weigh more than 1 G so the wings have to be made to increase lift to overcome this and continue the loop. As one goes over the top gravity reduces the weight of the aircraft and occupants so for them to remain at + G the wings have to develop (downwards) lift that is equivalent of more than 1G when straight and level. The recovery is self explained.
Simples.