Our brain consumes a significant amount of energy, accounting for about 20% of the body's total energy consumption. Most of this energy is used for information processing. While research shows that increased mental activity does lead to slightly higher energy consumption, this increase is minimal, region-specific, and often offset by energy decreases in other areas. Feeling exhausted after mental activity is likely due to mental stress rather than actual energy depletion. Pacing yourself can help avoid mental overload, stress, and fatigue.