A recent study conducted by Macquarie University indicates that obesity may actually be a disorder of the brain, characterized by a progressive deterioration of cognitive processes that impact eating behaviors. The study shows that memory inhibition, which is the helpful ability to “block out” memories that no longer serve us (and which originates in the hippocampus), is liked to overeating. When our brains are functioning properly, our food-related memories should be prominent when we are hungry then recede when we are full. That way, thoughts of food disappear when eating is no longer the top priority.
Earlier studies in animals have determined that a diet high in fats and sugars, low in fruits, vegetables and fiber, impairs that process of inhibiting memories. On a practical level, this could mean that a Western-style diet interferes with the ability of the hippocampus to inhibit those sensory memories triggered by the sight or smell of delicious food. Without that inhibition, it is much more difficult to resist food even if you are full.
The study looked at healthy young people. They completed learning and memory tests that rely on the hippocampus, and they rated their desire for palatable snack foods before and following a filling meal. The participants who usually ate a Western-style diet learned more slowly, and had more difficulty remembering than subjects who ate a healthier diet. They also showed much smaller reductions in their desire for snacks when tested full rather than hungry.
The key point of the study is that there is a link between memory performance snack food ratings. The author of the study, Ph.D. candidate Tuki Attuquayefio, writes:
Even though they were full, they still wanted to eat the sweet and fatty junk food. What was even more interesting was that this effect was strongly related to their performance on the learning and memory task, suggesting that there is a link between the two via the hippocampus.
In summation, the Macquarie University study mirrors the earlier animal research, proving that a high sugar, high fat diet may cause people to do more poorly on learning and memory tests, as a result of the effects of their diet upon the hippocampus. This phenomenon could explain the persistent desire for snacks, even when the subject has eaten a satisfying meal.