A reduced ability to achieve the same blood ketone levels via fasting may indicate changes in diet composition or fatty acid composition.

“It could be that they are more efficiently utilizing their ketones now. So you're accumulating fewer of them because you are drawing them off. You are utilizing them more. They have become a more preferred substrate.”

“It could be that they're actually just producing less of them. In other words, they're doing something different that they didn't realize they were doing in the past. Maybe they've changed their composition of fatty acids. Maybe they're eating more protein. Maybe they have more carbohydrate in their diet, things like that.”