Eating is necessary for survival, but it is also one of the great pleasures enjoyed by human beings. Research to date shows that palatable food can be rewarding in a similar way to drugs of abuse, indicating considerable comorbidity between eating disorders and substance-use disorders. Analysis of the common characteristics of both types of disorder has led to a new wave of studies proposing a Gateway Theory of food as a vulnerability factor that modulates the development of drug addiction. The homeostatic and hedonic mechanisms of feeding overlap with some of the mechanisms implicated in drug abuse and their interaction plays a crucial role in the development of drug addiction. Studies in animal models have shown how palatable food sensitizes the reward circuit and makes individuals more sensitive to other substances of abuse, such as cocaine or alcohol. However, when palatable food is administered continuously as a model of obesity, the consequences are different, and studies provide controversial data. In the present review, we will cover the main homeostatic and hedonic mechanisms that regulate palatable food intake behavior and will explain, using animal models, how different types of diet and their intake patterns have direct consequences on the rewarding effects of psychostimulants and ethanol.