Central circuits in control of energy expenditure: connecting energy and temperature homeostasis.

Energy expenditure (EE) is the dynamic physiological process that balances energy intake to maintain body weight and body temperature. Environmental changes induce EE adaptations that limit fluctuations in body weight or body temperature by balancing between body temperature defense and energy conservation. The central nervous system (CNS) orchestrates these adaptations by integrating multiple external and internal cues to coordinate thermogenesis together with other behavioral and metabolic processes. Key hypothalamic and brainstem nuclei form a distributed network that modulates autonomic output to peripheral organs, including sympathetic tone to brown and white adipose tissues. Here, we review known neural circuits and neurotransmitter systems, their integration with sensory pathways and functionally opposing output discrepancies that reveal knowledge gaps how the CNS switches between body temperature defense and energy preservation.