I was off of phen for a month. I maintained the first 2 weeks. The last 2 weeks I gained 9 lbs but that was because I had a personal crisis and I used food as comfort.

But the first 2 weeks I ate normal - even had some fast food and didnt gain anything during that time.
I also took phen about 7 years ago and lost about 45 lbs. I did gain all the weight back and then some but over a period of 5 years and went through a gallbladder removal and a divorce during that time.