If you’re eating a high-fat diet, you could be causing inflammation in your brain! High-fat diet? Think burgers and ‘some fries with that.’ Pizza and fast food chicken. Think potato chips and pretzels. Biscuits, doughnuts, and ready-to-eat microwave meals. These are all examples of foods that are part of a high-fat diet. We know these foods are bad for us, but we need them anyway because they are so convenient and they taste great.

Think about the effect of ultraprocessed high-fat foods on brain function. Not surprisingly, it’s bad news. This kind of high-fat diet causes inflammation in the brain! It is especially bad in older people and causes memory impairments. That’s scary!

There is no question that a typical Western high-fat diet causes cognitive impairments. It is an important topic on which there is a lot of research. The negative effects arise from saturated and trans fats. You’ll find these fats in ultraprocessed foods.

It’s not all bad. Certain high-fat diets, like a ketogenic diet, emphasize healthy fats (e.g., monounsaturated and omega-3s). Healthy fats have beneficial effects on memory and are protective for brain health. It’s the composition of the fats, rather than just their quantity, that is critical.

Burgers and fries are a common part of a high-fat diet

Aging and Metabolism

Children and young adults metabolise fats differently to older people, which has a lot to do with middle age spread!  As you age, the type of food you eat should change. However, for many of us, our diet remains the same. In fact, all that changes as we age is the waist size of our clothing!

Effect of a High-Fat Diet

The effect of a high-fat diet has been studied in detail in rats and the effects appear amazingly quickly.  Within three days, signs of inflammation appear in the brains of laboratory animals started on a diet high in saturated fats. We can see elevations of major histocompatibility complex II and an increase in microglial markers of inflammation. Additionally, and importantly, that effect applies only in aged rats, not young rats. 

An aged rat

From memory tests, we can tell that the rats develop a problem with consolidation of information in memory. Furthermore, a substance that causes inflammation, interleukin 1β (IL-1β) increases in the brain. Specifically, IL-1β accumulates in structures that play a critical role in memory formation. (Yip, the hippocampi.) Additionally, IL-1β also accumulates in areas involved in fear learning. (Yeah, you guessed it, the amygdalae). As I’m sure you’ve figured already, the longer animals eat a high-fat diet, the worse their memory gets. The same applies to us, of course!

Here’s the kicker. We can reverse the memory impairment if we let the rats run free and exercise. Doing so reduced the inflammation in their brains and their memory improved. We know from other research that exercise helps to reduce hippocampal inflammation. Better still, reverting back to a healthy diet sees an improvement in memory functioning, although the rats remain tubby.  Go figure! Of course, we can also use drugs to block the effects of IL-1β but who needs needs drugs if we can solve the problem with a change of diet and exercise? Right?

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