Carbs are great for metabolism! In fact high carb diets are about as good as a low carb diets for reversing metabolic issues. The real problem seems to be "balanced meals" that have moderate amounts of all macros.
We don’t really know the design process for QWERTY but it wasn’t about avoiding mechanical jams. Avoiding mechanical jams was the reason Dvorak was invented.
QWERTY if anything seems to be about being convenient for transcribing Morse code. Letters with a similar Morse code are grouped etc.