Macro partitioning

Fructose ingestion acutely and robustly increases FGF21 blood levels in both mice and humans, whereas glucose causes only a modest and delayed increase, establishing a liver-brain feedback loop for sugar consumption regulation.

Eating fructose triggers a rapid spike in FGF21, a hormone that helps regulate sugar intake, while glucose has a much weaker effect. This suggests your body uses FGF21 to specifically manage fructose consumption.