is this normal :/?

i am lossing weight without exercising this week by just eating junk food but not as many

i used to order 2 bigmacs and large fries and large cola but now just a 6 pack chicken nuggets and i lost weight in a couple of days like every a week or 2 i loss 1-2kg every time and i dont know if this is normal? i lost 20kg by eating junk food some days and i dont know if thats normal?

i used to be 90kg and now 70kg and im 5'10