The survival of an organism relies on its ability to promptly, effectively and reproducibly communicate with brain networks that control food intake and energy homeostasis. To achieve this, circulating factors of hunger and satiety reflecting nutrient availability must cross the blood-brain barrier (BBB) to reach effectors neurons. A defect in this process invariably leads to uncontrolled body weight. Here I will discuss the key role played in this process by a peculiar type of glial cells named tanycytes, which have their cell bodies lining the floor of the third ventricle and their endfeet contacting the pial surface of the brain. Recent studies indeed suggest that tanycytes, besides regulating hypothalamic BBB plasticity according to nutrient status, capture metabolic signals such as leptin from the bloodstream and transport them towards their cell body for release into the cerebrospinal fluid. Blockade of this conduit for peripheral metabolic factors into the brain of obese individuals is thought to contribute to the pathophysiology of central hormonal resistance.