The human body makes the exact amount of sugar it needs through a process called "gluconeogenesis." All sugars added exogenously (i.e. by eating carbohydrates, which break down to sugar), is harmful, as it throws this natural process out of whack.

And fiber is worse than useless. It's just sawdust that clogs up your GI tract and causes all sorts of digestive issues like IBS, leaky gut, crohn's/ulcerative colitis, etc. Oh and since you can't absorb any of it, it makes you fart and shit more. Yay!!
https://youtu.be/xqUO4P9ADI0?si=c27yjNx4_Qspyrx0
https://youtu.be/rr9yEqmro20?si=7i7osyqbDmawOAKm