Rats Self-Select a Constant Protein-to-Carbohydrate Ratio Rather Than a Constant Protein-to-Energy Ratio and Have Low Plasma FGF21 Concentrations.

This study showed that self-selecting rats established PE ratios larger than those considered sufficient to achieve optimal growth in adult rats (10-15%), and the ratios were highly dependent on carbohydrates, apparently with the aim of maintaining a constant and high PC ratio. This was associated with a minimization of plasma FGF21.