Overeating can cause the brain to lose control and cause damage potentially leading to diabetes, heart disease, and other ills - according to new U.S. research.

Eating too much appears to make a usually dormant immune system pathway in the brain, sending out immune cells to attack and destroy non-existent invaders. The finding could help explain why obesity causes so many different diseases, and also may offer a way to prevent obesity itself.

Lead researcher, Dongsheng Cai of the University of Wisconsin-Madison, claims, "This pathway is usually present but inactive in the brain."

Cai's team worked in mice, seeking to explain studies that have found obesity causes chronic inflammation throughout the body. They homed in a specific compound found in the hypothalamus, the part of the brain linked with metabolism. 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."

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