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Sodas: The conventional variety are, of course, not an option if you want to follow a paleo diet. There are some made of 100-percent fruit juice, with carbonation added, that would be a healthier choice, although if weight loss is your primary goal, I would limit anything this sweet to only very occassionally (i.e. once or twice a week, at most). I don't see that the carbonation, in and of itself, would affect you in terms of weight, but note that it is "basic" in terms of its pH, which means it will counteract your natural stomach acids. If taken with food, it may have some inhibitive effect on your ability to fully and properly digest your food.
Potatoes: Aren't the sort of root vegetable favored in a paleo diet. Carrots, turnips, parsnips, rutabaga, etc., are better choices. Yams (or sweet potatoes) are okay in moderation, but keep in mind that they (like fruit juices) are higher in natural sugars, which will cause more dramatic insulin spikes, which will inhibit the fat burning effect... you'll still see results, but not as quickly, the more you include these sorts of food. Standard potatoes (white, red, yellow) are quite starchy, and will have a similar effect, as they convert to sugar in the body almost immediately upon consumption.
There are good alternatives out there to help you cope with initial cravings. Check out these cookbooks for some great ideas:
http://www.marksdailyapple.com/the-primal-blueprint-reader-created-cookbook/ Good luck, and keep us posted!