This definitely can have a huge impact on your ability to focus and work productively.

However, I think the data here on the paleo diet is somewhat outdated "paleo 1.0" information, dating from back when people in the evolutionary medicine community were confounding ill effects from specific grains and other foods with carbohydrates. I recommend the diet advice of Stephan Guyenet, Shou-Ching and Paul Jaminet, and Kurt Harris over the information at that link.