Today we're talking about a fundamental topic for anyone who decides to follow a low-carbohydrate or ketogenic diet, in which therefore the daily carbohydrate quota is pre-set, low and must not be exceeded.
When we talk about carbohydrates we know that they are not all the same and not all have the same effects on our body.
When we embark on a diet that must take into account the carbohydrates introduced, we always refer to NET CARBOHYDRATES, i.e. those carbohydrates that our body is able to digest and absorb (and therefore transform into energy).
What are the carbohydrates that our body is NOT able to digest or only partially digests?
First of all the fibers that don't come absorbed in the small intestine. Intestinal bacteria ferment transform soluble fibers into SCFA (short-chain fatty acids), which provide minimal calories and have neutral or beneficial effects on blood sugar.
The other carbohydrates that are not absorbable are polyols which include the most common sweeteners. Here is the article on sweeteners with the net carbohydrates and the glycemic index of each.
Apart from synthetic sweeteners such as sucralose, for example erythritol and stevia are not absorbed while others such as maltitol and xylitol are only partially absorbed (therefore the polyols deriving from the latter should not be subtracted in full from the calculation of carbohydrates).
In general, therefore, when we have TOTAL CARBOHYDRATES we could subtract FIBERS and POLYOLS (these in full or less depending on the sweetener from which they derive)
And this happens if you look at an American nutrition label where this count is evident 
In the European and Italian nutritional tables, on the other hand, FIBERS should not be subtracted because they are already counted separately and not included in the calculation of carbohydrates.
Here is an example in which the polyols must be subtracted (because they derive from erythritol) but the fibers are already separate 
