It is all about changing your life style….A substitute is something you use in order to have something similar to what you have always eaten. An alternative is something different which satisfies the same perceived need. Example: I love risotto but I am not eating white rice at the moment. I could use cauliflower ‘rice’ as a substitute (probably not very satisfying) or something else find on the internet. If I used a substitute, I would just be looking forward to when I could have risotto again and I would not have really changed by life style at all.
Instead I have looked for an alternative. I love pumpkin and clam risotto and pumpkin, chicken and bacon risotto. So, after careful thought, I made soup recipes as an alternative for both. Works for me. See my recipes for the details.