It's not so much a problem of calories, but more so due to the actual action of chewing. There is an intimate connection between your jaw and your intestines (and pancreas). When you start chewing your body releases digestive enzymes in preparation fro digestion of solid food. Then the next time you go to actually eat solid food, your digestive enzyme pool is depleted, and your digestion in hampered. Additionally, your pancreas will release insulin as a response to chewing, something you certainly don't want. The breath strip might be a better option due to no chewing, but then you have problems with the artificial sweeteners possibly causing insulin secretion. Also, in a fasted state the body absorbs any ingested materials much more quickly and efficiently. I'm not so sure that you want your body absorbing neurotoxins, like so many artificial sweetners are, at any great efficiency. To give you an example, when I used to IF I would sometimes eat a piece of sugarless gum. Well, predictably, I would ALWAYS get and intense headache, loss of concentration, and lethargy immediately after beginning to chew the gum.
There are dreams we’re taught are normal, whether it’s money or success or any of those things, but we shouldn’t believe in those things if they are not important to us. There is an ocean between our real lives and what is expected of us.” -Tim Lambesis