extreme weight gain

Last September I went on a mass gaining workout and diet. I started out around 195lbs and for the first week on around a 3500 to 4000 cal diet I didn’t gain a pound. During the second week bang, things changed. I put on about 4lbs and then it tappered off to around 1 to 2lbs a week. During the middle of January I went on a cutting phase and cut my diet back to around 2000 cal and added cardio and ,for the first week, once again, no change in body weight. During the second week repeating itself, like magic I droped 4lbs. This has happened to me every time I have made extreme changes in my diet. Has anyone else experieced similar things? Do you have an explanation for this?

aliens!