Keeping your weight is more about attitude & self-education.
Mrs. P has always struggled to keep her weight at a consistent level. She's tried every diet going, from Weight Watchers to the Atkins diet. The latter drove her gaga, lack of carbs are no good for the metabolism.
The only thing that works is smaller portions. For instance, when I cook chips or roasties I will give her half the amount. If I have 8 roasties she'll only get 4. It's about training your brain to except smaller amounts. If you get peckish between meals, she will now have a glass of water or weak squash.
Years ago, when I started this method, she lost over a stone in 3 months. And she is a wheelchair user so she can't exercise like the able bodied