“Where do reward signals for food come from? In this lecture I will discuss findings from work in humans and in animals demonstrating that the value of food lies, not in the food itself, the pleasure it evokes or the nutrients it supplies the body, but rather in the organism’s ability to transform nutrients into vital resources, such as cellular fuel. This physiological process requires the integration of internal and external signals through gut-brain reinforcement learning. I will conclude by considering the implications of this process for understanding the link between the modern food environment and the obesity and diabetes pandemics.”