This invention is a device and method for selectively and automatically reducing absorption of unhealthy food in a persons gastrointestinal tract, while allowing normal absorption of healthy food. In an example, such a device can comprise: a food-identifying sensor an absorption-reducing substance an implanted reservoir and a release-control mechanism that selectively and automatically releases the substance into the persons gastrointestinal tract when the sensor detects that the person is consuming unhealthy food.
