Is the caloric content of chewing gum in reference to what is provided from chewing alone, or from ingesting it?
Just a WAG, but I doubt there’s much in the way of calories in the gum itself. Pretty much all the calories have to come from the sugars it contains. And whether or not you swallow the gum, you’re going to ingest this sugar and get the calories by chewing it…
If it’s measured by bomb calorimeter, they just burn it. This would release all the stored energy including the polymers from the gum and stuff like that.
That said, that energy from the food you eat depends on the food. We don’t cleanly burn your food; a certain amount passes through undigested. Back to your question - you won’t get the energy from the gum since you spit it out, but you will digest the leached sugars. Likewise with roughage from bran, since a large amount of it passes undigested, the true calorific value would be less than that measured.
Random cite
Another tidbit about gum is if you are hungry don’t chew gum to deter it. just swallowing the juices mixed with your saliva will get your stomach churning. worse than before you chewed the gum.