Glucose uptake across the blood-brain barrier primarily uses GLUT1 transporters, which are largely independent of insulin, diet, and exercise.

“at the blood-brain barrier glut4 plays a minor to no role in glucose uptake the blood-brain barrier in contrast has a predominance of glute ones one expression is not controlled by what you eat it's not controlled by how you exercise to a large extent and it's not controlled by the same mechanisms that govern insulin regulated glucose signaling”