It is still possible to gain if you eat a lot of naughties for the whole Christmas period, I didn't do too well the one just gone...mainly due to a record number of bottles of Baileys I expect!!!
However, things like roast potatoes you probably won't find you eat often and so a couple small ones for a special occasions , cut into teeny bits and well chewed, usually are OK.
If you start with really tiny amounts as well you should be able to enjoy a little taster of your old faves but the amounts will be so much less and hopefully you will enjoy it overall more because you won't be stuffed to the gills all through it.
I can only have one little mince pie for example, where before I could easily eat 2 or 3 without really thinking about it.
Plus you will be so much more into going out and glamming up at that time of year etc you will find that some of the goodies you can take or leave.
That's a nice feeling x