Overeating Causes Brain Chemistry Imbalances

Dongsheng Cai, lead researcher of the University of Wisconsin-Madison, claims that this immune pathway is present but typically inactive in the brain. The researchers have used mice to explain studies that indicate obesity causes chronic inflammation throughout the body. They focused on a specific compound in the hypothalamus, the area of the brain that regulates metabolism.

Typically, this compound is present in high levels but is dormant. However, when the mice were given a high-fat diet, this compound became highly active. Once the compound became active, the body began ignoring signals from leptin, a hormone that helps regulate appetite and insulin. Cai thinks his team as discovered the switch responsible for the diseases associated with overeating.

Cai and his team claim that the hypothalamic compound could be behind an entire line of modern diseases linked to over-nutrition and weight gain. It’s unknown why this compound can be found in the brain and the immune system. Cai presumes the compound once had a role in guiding immune defense. However, in today’s society, this pathway is triggered by a different problem – overeating.

Normally, this compound is present in high levels but inactive. When the mice were fed a high-fat diet, it became extremely active. With this compound active, the body ignored signals from leptin, a hormone that normally helps regulate appetite and insulin. Cai believes his team has discovered a master switch for the diseases caused by overeating.

According to his team, "[This] Hypothalamic [compound] could underlie the entire family of modern diseases induced by over-nutrition and obesity." It's not known why this compound can be found in the brain and the immune system. Cai adds, "Presumably it played some role to guide the immune defense. In today's society, this pathway is mobilized by a different challenge - over-nutrition."

Although overeating can create chemical imbalance in the brain, the reverse is also true. A brain imaging study in the U.S. Department of Energy’s Brookhaven National Laboratory reveals a key difference between normal obese subjects and those who are compulsive binge eaters. In the case of binge eaters, the mere sight or smell of desirable food can cause a large spike in dopamine – the brain chemical associated with reward and motivation. The findings suggest that this dopamine change may trigger incidence of binge eating.

Researchers provided one obese group with stimulating food and the drug, methylphenidate, which blocks reuptake of dopamine and allows it to linger longer. The triggering food caused significant spikes in dopamine levels within the caudate and putamen regions of the brain in overeaters, but not in normal eaters. Subjects, who suffered with the most severe cases of binge eating, had the highest dopamine levels in the caudate.