I have two Hubs that will give you some recipes (and nutritional information) for vegetables that you can substitute for potatoes or rice.
As you probably know (and the reason why you are probably asking the question?), potatoes and rice are very high starch. Thus, they have a high glycemic index. By replacing them with celery root or other vegetables (see my Cauliflower recipe for Cauliflower mash...a great sub for mashed potatoes), you lower your overall caloric intake.
My two hubs:
1. Celery Root As A Substitute for Potatoes:
2. How to Make Broccoli and Caulflower That Even Your Kids Will Love, https://delishably.com/vegetable-dishes/broccoli-b... (the first two recipes--the ones without the high calorie blue cheese)