Paying the brain's energy bill

How have animals managed to maintain metabolically expensive brains given the volatile and fleeting availability of calories in the natural world? Here we review studies in support of three strategies that involve: 1) a reallocation of energy from peripheral tissues and functions to cover the costs of the brain, 2) an implementation of energy-efficient neural coding, enabling the brain to operate at reduced energy costs, and 3) efficient use of costly neural resources during food scarcity. Collectively, these studies reveal a heterogeneous set of energy-saving mechanisms that make energy-costly brains fit for survival. •Brains are metabolically expensive.•Peripheral functions are sacrificed to fuel brain function.•Efficient-coding reduces the operational costs of the brain.•Costly neural functions are reduced during food scarcity.•Food-seeking neural functions are specifically enhanced in times of hunger.