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Study: High-Fat Diet Can Prove Harmful To The Brain

AUGUSTA, Ga. (CBS) – Need another reason to put down that fried doughnut?

A high fat diet not only causes people to become overweight, it also appears to prompt immune cells in brains to become sedentary and consume connections between neurons, according to a study out of the Medical College of Georgia at Georgia Regents University.

Dr. Alexis M. Stranahan, a corresponding author of the study in the journal Brain, Behavior, and Immunity, provides input on why fat is not good for the brain.

"Normally in the brain, microglia are constantly moving around. They are always moving around their little fingers and processes. What happens in obesity is they stop moving. They draw in all their processes; they basically just sit there and start eating synapses. When microglia start eating synapses, the mice don't learn as effectively."

Researchers say going back on a low-fat diet for two months can reverse the trend of shrinking cognitive ability as weight begins to normalize, at least in mice.

"On the one hand, that is very scary, but it's also reversible, meaning that if you go back on a low-fat diet that does not even completely wipe out the adiposity, you can completely reverse these cellular processes in the brain and maintain cognition," Stranahan says.

Researchers say the study looked at normal male mice. One group ate a diet in which about 10 percent of the calories came from saturated fat, and the other group ate food that was 60 percent fat.

The study says researchers chose food that had similar levels of other key ingredients such as macronutrients and protein.

Scientists took a series of metabolic levels at four, eight and 12 weeks, such as weight, food intake, insulin and serum glucose levels in the mice.

Researchers say they also measured in the hippocampus, which they say is the center of learning and memory, levels of synaptic markers, proteins found at synapses that correlate with the number of synapses.

The study found, "By 12 weeks the fat-eating mice were obese, had elevated cytokine levels and a reduction in the markers for synapse number and function."

"When you get out to 12 weeks, you start seeing great increases in peripheral obesity. While you don't see insulin resistance, you also start seeing loss of synapses and increases in inflammatory cytokines in the brain," according to Stranahan.

Scientists found "obesity yields extreme overkill in microglia, which are typically extremely discriminating and helpful to neurons."

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