High fat diets trigger inflammation in the brains of older people and cause memory impairments. These diets also go by names such as ketogenic diet, Atkins diet, and Banting diet. While high-fat diets have become very popular, and for some people have been a means of losing weight, their effect of brain function needs to be considered since it is known that high-fat diets are associated with cognitive impairment.
Children and young adults metabolise fats differently to older people, which has a lot to do with middle age spread! As you age, your dietary intake should change, but for many of us, our diet remains the same and all that changes as we age is the size of our clothing.
The effect of a high-fat diet has been studied in detail in rats and the effects appear amazingly quickly. Within three days of being changed to a diet high in saturated fats, there are signs of inflammation in the brains of these laboratory animals (major histocompatibility complex II is elevated and microglial markers of inflammation are increased), but only in aged rats, not young rats. On memory tests, the rats showed signs of impaired consolidation of information in memory and the researchers found that interleukin 1β (IL-1β), a substance that causes inflammation, was increased in memory regions of the brain (the hippocampi) and in regions involved in fear learning (the amygdalae). The longer the animals are kept on a high-fat diet, the worse their memory impairment.
Blocking the action of IL-1β with a receptor antagonist, reverses the memory impairment. Also, when the rats are allowed to exercise, inflammation is reduced in their hippocampi and their memory improves. We know from other research that exercise helps to reduce hippocampal inflammation. Reverting back to a normal diet sees an improvement in memory functioning, although the rats remain tubby. Go figure!