Your question was: How to stop gaining back weight after Nutrisystem?.
One thing I noticed is that when I am maintaining, something that works great is to keep my scale in the kitchen. I was able to keep the weight off for quite a long time while I had that in there, but one day, my husband who is very overweight, "Accidentally" dropped something on it and it broke. That was when the weight started creeping back up as I had no concept that I was gaining until I could not wear my clothes anymore.
I'm getting a really nice scale and it is living in my kitchen. If it accidentally gets broken again, someone will be buying a new one right away!! Haha!..
I weigh myself daily (twice a day actually - morning and night). For me it keeps me on track. I am able to make adjustments and catch myself before things get out of hand. I have got to know my body and what it's normal fluctuations are. If I am not drinking enough water - the scale is the first place I notice it.
Katie mentioned diabetics having to watch what they eat. I guess my scale is my diabetic equivalent of a glucose monitor..
Keep up the good fight Pop-Tart...