Steady energy. By the time your child turns 4, his body is burning through glucose twice as quickly as yours. Derived from healthy carbohydrates, glucose is the brain’s main source of energy. Because kids metabolize it so fast, it’s important that they have a continuous supply, which means eating regular meals and snacking (on healthful foods) every few hours. An extended period without food can cause blood sugar levels to dip, resulting in impaired self-control, difficulty focusing, and downright crankiness.
“The role of nutrition in children's neurocognitive development, from pregnancy through childhood” by Nyaradi A, Front Hum Neurosci (2013).