The hypothalamus is a small area of the brain that controls important functions like metabolism, homeostasis, emotions, circadian rhythms, and hormone secretion. It regulates these functions through coordinating the autonomic nervous system and endocrine system. Studies have shown that exercise can restore neuron sensitivity in the hypothalamus to reduce food intake and promote weight loss. Depression has also been linked to changes in hypothalamic gene expression. Additionally, research on fear responses in rodents suggests that the hypothalamus, not the amygdala, is the main brain structure that controls fear behavior.