Figure 1.Gastrointestinal signals regulate food intake. The majority of signals from the GI tract regulate the size of individual meals. Mechanoreceptors quantitating stretch of the stomach, and chemoreceptors activated by nutrients in the GI tract, transmit information via vagal and sympathetic afferents to the hindbrain nuclei. This information is then transmitted to the hypothalamus and other forebrain structures for integration with additional signals regulating food intake. Vagal afferents from the liver signal the presence of specific nutrients. Glucose and ketones act as signals to the CNS directly on responsive neurons in the hypothalamus. Gastrointestinal hormones such as CCK bind receptors in the liver to activate vagal afferents, or access the CNS via the circulation. Other hormones such as GLP-1 inhibit feeding by slowing gastric emptying. Figure reproduced with permission from reference 7.