You may have felt it after a rare indulgence in fast food — a slowing down, not just physically, but mentally. It turns out research supports the connection between your cheeseburger binge and foggy thinking. A recent study finds that fat is bad for our brains.
During the study, researchers put one group of mice on a diet composed of about 10 percent of calories from saturated fat. The other ate a fast-food type diet of 60 percent fat. Both diets had similar levels macronutrients and protein so that all other dietary factors were equal. (1)
Scientists checked the weight, food intake, insulin and serum glucose levels of the mice at four, eight and 12 weeks. They also took note of markers in the hippocampus, the region in the brain where learning and memory take place.
Here’s what happened. Microglia are the immune cells of the brain. When activated by disease, microglia find injured neurons in the brain and strip away synapses, the connections between neurons. Microglia remove weak connections that can impede brain function. (2)
Normally, microglia buzz busily about the brain keeping things in order, removing damage. A high-fat diet creates inflammation throughout the body (3) and, scientists have discovered, the same holds true for the brain.
A high-fat diet that leads to obesity sets the microglia on an indiscriminate warpath. Instead of focusing on injured neurons only, the microglia attack them all.
Neuroscientist Dr. Alexis M. Stranahan, corresponding author of the study, shared with Science Daily, "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," reported Stranahan.
This means an inflamed brain is a brain losing synapses, and lost synapses mean slower cognition. Stranahan offered this metaphor: "Instead of doing garbage disposal, [the microglia] are taking your mailbox, your front door, your kitchen sink and all the stuff that you need, and not doing their job of getting rid of trash."
The good news? You can restart your brain by returning to a low-fat diet.