“Highly palatable” foods – those containing fat, sugar and salt – stimulate the brain to release dopamine, the neurotransmitter associated with the pleasure center, he found. In time, the brain gets wired so that dopamine pathways light up at the mere suggestion of the food, such as driving past a fast-food restaurant, and the urge to eat the food grows insistent. Once the food is eaten, the brain releases opioids, which bring emotional relief. Together, dopamine and opioids create a pathway that can activate every time a person is reminded about the particular food. This happens regardless of whether the person is hungry.
Not everyone is vulnerable to “conditioned overeating” – Kessler estimates that about 15 percent of the population is not affected and says more research is needed to understand what makes them immune.
But for those like Kessler, the key to stopping the cycle is to rewire the brain’s response to food – not easy in a culture where unhealthy food and snacks are cheap and plentiful, portions are huge and consumers are bombarded by advertising that links these foods to fun and good times, he said.