To butter or not to butter? That is the question. Researchers found that high-fat diets can cause active immune cells in the brain to become inactive and start consuming neuron connections. Switching back to a low-fat diet after two months into the high-fat diet path can reverse the cognitive shrinking activity.

The problem starts when too much of the consumed fat produces chronic inflammation. This leads to an autoimmune response from the microglia - the central nervous system's first and foremost form of active immune response. Microglia's interior is highly acidic which aids in their function to consume and purge infectious agents found in the brain and promote neuron health.

"Microglia eating synapses is contributing to synapse loss and cognitive impairment in obesity," said Medical College of Georgia's Alexis M. Stranahan, the study's corresponding author.

In the mice study, the test subjects failed to learn effectively when they became obese. The mice were fed the minute equivalent of healthy and fast-food diets in humans. The diets contained similar proteins and macronutrients. One group of male mice was fed a diet wherein 10 percent of the calories are from saturated fat while the other group consumed 60 percent fat.

During the 12th week, researchers found higher levels of cytokines and reduced numbers of synapses among the mice subjects. When the mice get obese, the microglia tends to focus on overeating. Half of the mice who ate a high-fat diet were switched back to a low-fat diet and it took two months for their weight to normalize. Despite the switch, their overall fat levels remained higher compared to the mice who didn't gain weight.

Stranahan stressed that it is a terrifying consequence however, it is also reversible. Going back to a low-fat diet will not get rid of the obese state but it can wholly reverse the cognitive shrinking ability in the brain. The study delivered the first few evidence of fat's negative effects on the brain. In a normal scenario, microglia moves around constantly in the brain. During obesity, microglia stops moving and begins consuming synapses.

The study findings were published in the Brain, Behaviour, and Immunity journal.

Photo: Rebecca Siegel | Flickr

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