my body type is ectomorph with 5 feet 9 inch and 57kg. very skinny.

i plan to reach 70kg weight by lifting and high protein diet. but i wonder, will i lose back if i reduce my lifting workout and eat just normal 3 meals instead of 5-6 meals per day ?

in another words, will i stay on at 70kg if i stop working out and eating 3-4 meals per day ?