The explanation I have heard is that when you don't consume a lot of carbs, your muscles aren't going to be running on glucose and so they decrease sensitivity so that glucose goes to the brain which will always need some glucose no matter what. This is how we partition glucose in ketosis. Why waste glucose on muscles when glucose is scarce 99% of the time? Also when your muscles are running on fats, they aren't going to be so ready to just take in glucose right away, they're burning the fats. It's a transient and unimportant thing since 50g of carbs isn't that much, and it is absorbed slowly in real food. If you started eating more carbs your sensitivity would go back up.
Here is the link. http://high-fat-nutrition.blogspot.c...tance-and.html
Fasting glucose is a better measure for metabolic health.
Stabbing conventional wisdom in its face.
Anyone who wants to talk nutrition should PM me!