Carb, fat and protein changes in vegetable fermentation, specifically a ballpark reduction arc in carbohydrates
on the &quot;Less important, but of keen interest&quot; question:
let's talk carbs instead of cals here.  cals are potential chemical energy stored in carbohydrates, fats, proteins, etc.  in vegetable fermentation, the fat and protein content is not a significant contributor to potential calories, so i'll confine this to carbohydrates
microbial fermenters' (effective, not comprehensive or quantitative) ...
most who do this don't track a carb burn rate, but they definitely notice when the jars quit bubbling.  CO2 output rate is directly proportional to carb burn rate, but those are very difficult to measure without specialized equipment
there are two ways that fermenting usually stops, when fermenters

run out of food (mostly carbs)
byproducts (here, lactic acid) are concentrated enough to halt reproduction

so if the jar's quit bubbling, it's important to understand that it might not be down to near zero carbs
inputs are

carbs
minuscule amounts of protein and trace minerals

outputs are

more fermenters
carbon dioxide, which is not retained by most canners
lactic acid
compounds that lend funk to flavor and aroma

note that fermenters consist mostly of:  water, lipids (structural and energy storage), and protein (structural and information storage)
to answer the keen interest ...

net change in carbs?  yes.  down
net change in protein?  yes.  up, but not by much
net change in fat/lipids?  yes.  up, but not by much