sausage grinder and brainThere have been many disturbing studies on the effects of a high-fat diet on the brain. I’m thinking in particular of the 2009 study that suggested the American diet can be as addictive to the brain as heroin.

But a new study presented at the annual meeting of the Endocrine Society is even more concerning — and may provide a “missing link” in our understanding of the obesity epidemic.

Researchers led by Joshua Thaler of the University of Washington fed an American-style high-fat diet to lab rats over the course of eight months. They discovered that the diet not only harmed the rats’ bodies, but also appeared to cause measurable injury to their brains — including damage to nerve cells that control body weight. As Science Daily explains:

Within the first three days of consuming a diet that had a similar fat content to the typical American diet, rats consumed nearly double their usual daily amount of calories, Thaler reported. Rats and mice fed the high-fat diet gained weight throughout the study. These rodents developed inflammation in the hypothalamus, the part of the brain containing neurons that control body weight. At the same time, a group of support cells called glia and scavenger cells called microglia accumulated in the hypothalamus and appeared to become activated. Although this collective response to brain inflammation — called gliosis — subsided days later, it recurred after four weeks.

“Gliosis is thought to be the brain equivalent of wound healing and is typically seen in conditions of neuronal injury, such as stroke and multiple sclerosis,” Thaler said. “We speculate that the early gliosis that we saw may be a protective response that fails over time.”

In their experiments, Thaler said they also detected damage to, and eventual loss of, critical weight-regulating neurons. These neurons, called pro-opiomelanocortin (POMC) neurons, were reduced in number by month 8 of the high-fat diet in mice, according to Thaler. These results were not present in same-age rodents fed standard chow.

True, this study was of rats, not humans — though with good reason as picking apart the brains of humans is typically frowned upon.

If further research bears out this indication that a high-fat diet actually damages the part of the brain that controls weight regulation, then it would force us to change how we view obesity as a condition. The notion that obesity represents a failure of willpower on the part of the individual won’t hold up if there’s evidence that a high-fat diet itself causes the loss of specific neurological function. Perhaps it’s time for a new round of those “This is your brain” PSAs from the ’80s …