Hello Ibo and welcome! I think you are taking right step forward, by heading into carnivore lifestyle and by seeking community here. As for the diet soda, it is something you will want to aim at getting rid of. Club soda, plain seltzer, and sparkling water are good alternatives. But don't worry if you are not wanting to give it up immediately, sometimes it's easier to eliminate the worst things first, like foods with seed oils and sugars first, then naturally high carb foods, and so on. some people like Prof Bart Kay, think it makes more sense to go carnivore gradually like that to avoid drastic change that may shock the digestive system. The diet soda will eventually sabotage your efforts. Kelly Hogan of myzerocarblife on YouTube talks about how much harder Carnivore was for the first year or so because the artificial sweeteners gave her cravings. I'm not sure what is in coke zero, but aspartame is a neurotoxin and most other sweeteners negatively impact the gut.