The dietician is telling you the old way of thinking. If you don't eat many carbs, the body will convert protein and fat into glucose to feed your brain and other cells. Most of my meals have NO potato/pasta/rice/bread and I'm healthier than I've ever been. Here are some examples:
With bolognese sauce, I have shredded white cabbage.
On shepherds pie, I use mashed cauliflower.
With stews/casseroles, I have carrots, green beans, butternut squash, etc.
With homemade curry, I blitz raw cauliflower in the food processor and then stir-fry it to make cauli rice.
Weekend breakfast is scrambled egg, lean bacon, sausage, mushrooms, tinned tomatoes (no toast or hash browns).
With a roast dinner, I do have a little bit of spud - but I roast 2-3 NEW potatoes in their skins.