Is Food Addictive? New Study Says 'Yes' in Rats

By Torey Jones, MS RD LDN

In a recent study, researchers Paul Johnson and Paul Kenny from the Scripps Research Institute in Florida examined the effects of a high-fat diet on brain reward systems in rats.  Johnson and Kenny were interested in determining whether food has addictive properties, similar to that of known drugs.  They also tested whether food overconsumption has the ability to affect nerves signaling satisfaction and satiety in the brain.

Johnson and Kenny divided rats of equal weight into groups – those that had unlimited access to a “cafeteria diet” (energy-dense foods such as sausage, bacon, cheesecake, pound cake, frosting and chocolate) and those with standard rat chow and limited access to fatty foods. Not surprisingly, weight increased rapidly in rats with unlimited access to the cafeteria diet. In fact, the caloric intake of these rats nearly doubled that of the rats with limited access to cafeteria foods.

The ob ob mouse (for illustration purposes only; not associated with this study)

Johnson and Kenny went on to analyze the effects of a cafeteria diet on brain reward function, or the feeling of satisfaction after a stimulus. The rats that became obese showed a worsening of brain reward function over time. Simply put, while the rats continued to eat these foods, the cafeteria diet no longer produced the same internal satisfaction. The researchers point out that this deficit in brain reward function is the same mechanism that plagues cocaine or heroin addicts; the amount that once provided a sense of satisfaction no longer produces the same reward response.

Researchers conclude that “over-stimulation of brain reward systems through excessive consumption of palatable, energy-dense food induces a profound stage of reward hyposensitivity and the development of compulsive-like eating.” In other words: eating a calorie-dense, high-fat diet led to lesser internal satisfaction from these foods but unchanged consumption over time.