The Brain Runs on Fat: Revisiting the Preferred Fuel of Human Evolution For decades, we've been told that glucose is the primary—and preferred—fuel for the human brain. But what if that story is incomplete? Emerging research and a deeper look at our evolutionary biology suggest that ketones—not glucose—may be the brain’s true super fuel , especially in states of fasting, endurance, or low carbohydrate availability. 🦴 A Look Back: Human Evolution and Energy Our ancestors didn’t eat every 3 hours. Instead, they evolved to thrive in environments where food availability was unpredictable , and long stretches without carbohydrate were common. During those times, the body would enter nutritional ketosis , converting fat into ketone bodies like beta-hydroxybutyrate (BHB) —which are not just an alternative fuel, but in many ways a superior one . Persistence hunting (chasing prey for hours): fueled by fat, not carbs. Rapid brain growth in Homo erectus : likely supported by nu...