The thing with low carb is that it tends to be high fat, as you need to have something to get your energy from - if you're still eating carbs in other meals, then most of my low to no carb recipes will only make you fatter...
If you want carb substitutes, then try boiling and mashing cauliflower (keep the pan over the heat when you mash it as a lot of liquid comes out) for a mash substitute - I add a tsp of chicken bouillon and a knob of butter, chives and sour cream if I'm feeling flash.
Swede can be treated as potato, you can make chips, roasties and mash out of it.
Glazed turnips make a lovely roast potato substitute.
More carby, but v. nice is butternut squash - halve, remove seeds, paint with oil and bake in the oven then cut into chunks to serve (it's a bit tasteless if you just boil it).
Cabbage or leeks chopped and stir-fried/boiled make a good tagliatelle type substitute for pasta
Shave courgettes from top to bottom with a potato peeler and fry (don't boil, they will disintegrate) for another pasta substitute - you will need lots, they shrink horribly.
Fresh cauliflower grated small and stir-fried makes a good rice substitute.
Similarly, run fresh sprouts through the food processor/blender til chopped small, then stir fry for a 'bed' to put your meat n' sauce on.
Also spinach as a base - I use frozen spinach, melt it down in a frying pan with a bit of garlic then add a 1/4 cup of cream and a 1/4 cup of grated parmesan (I use the dried stuff that comes in the shaker) and stir til all gooey and melted in - yummingtons!
I can post some actual low-carb recipes if you'd like...?