Hi
I was told to add things like real butter and other higher calorie items to maintain my weight if needed.
Although so far I have not needed to as my weight has remained quite stable now without me having to do anything, so it might be that the body is able to manage itself once your natural target has been reached, that's the bodies target not yours.
Don't forget that most target weights are not easily attained as after significant weight lose you will be carrying around about a stone of loose skin, so trying to attain a weight based on the normal charts could result in you being under weight. so aim for a weight at the top end or just above you doctors weight chart.
In my case although a healthy BMI is 25 or below, my Dietician told me to stop loosing weight when my BMI was just over 26, so its still showing me as slightly over weight, but if my loose skin was removed I would be well in the healthy BMI range.
Hope this has helped.
Paul