For a long time, fats were considered detrimental the a healthy diet. In the 1970s and 80s, fad diets like the Scarsdale and grapefruit diets were all the rage. There was a new market of low-fat food products (which typically contained more sugar and carbohydrates). Researchers later questioned the potential drawbacks of severely restricting all dietary fats. Nevertheless, this craze has left people with negative views on dietary fats. So it may be shocking to learn that recent studies indicate that a high-fat diet could help preserve good brain health.
The Connection Between Fats and Cognition
First, it’s important to note the different types of fats. One kind benefits brain health, and the other may worsen it. Some small studies in rodents have linked a high-fat, fast-food diet to brain inflammation and poorer memory. The authors found that metabolic issues disrupt the function of the hippocampus, the part of the brain that’s vital for forming memories.
Fast food, fried food, and highly processed food tend to contain large amounts of saturated fat and partially hydrogenated fats, such as trans fat. These ingredients can increase the risk of type 2 diabetes, heart disease, metabolic syndrome, and, according to this research, worsen cognition. Metabolic syndrome has already been linked with poorer memory, cognitive decline, and an increased risk of dementia.
“We have long known about the association between metabolic syndrome, being overweight, and how unhealthy fatty diets may be associated with dementia,” said Derek Cheng, DO, a neurologist at Stamford Health, to Medical News Today. He commented on a recent study where the team put mice on a high-fat diet for two days. “However, it is interesting in this study to see just how quickly, in just a few days, memory formation may be impacted by a poor diet.”
Meanwhile, a diet high in healthy fats from fish, nuts, and other whole foods can improve mental processing. The human brain is composed of approximately 60% fat (dry weight), and consuming omega-3 fatty acids helps support its function. Despite accounting for only 2% of the body’s weight, the brain uses around 20% of its energy. This makes it sensitive to what the digestive system is breaking down for fuel. It’s no surprise that many people with digestive disorders, such as IBS and gastroparesis, report brain fog and grogginess, as documented in a 2025 study.
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Can You Prevent Alzheimer’s with a High-Fat Diet?
Researchers at the University of Missouri tested how a ketogenic diet can affect brain health. The diet is known for being high in fats and low in carbohydrates. Their study, published in the Journal of Neurochemistry, found that this approach can slow or even prevent cognitive decline in people genetically predisposed to Alzheimer’s disease. However, more in-depth research is needed to confirm and extend this, particularly given that the study was conducted in mice. The researchers found that female mice with the APOE4 gene (which is highly associated with Alzheimer’s) showed improved brain health when eating a diet high in healthy fats. This was not the case with the mice eating a diet high in carbs. (Interestingly, males did not show the same level of improvement.)
“When we eat carbs, our brains convert the glucose into fuel for our brains, but those with the APOE4 gene, particularly females, struggle to convert the glucose into brain energy, and this can lead to cognitive decline down the road,” said doctoral student and co-author Kira Ivanich in a press release. “By switching to a keto diet, ketones are produced and used as an alternative fuel source. This may decrease the chance of developing Alzheimer’s by preserving the health of brain cells.”
This study promotes the concept of “precision nutrition.” This method counters the “one-diet-fits-all” idea and creates dietary plans based on a person’s specific biology, genetics, lifestyle, etc. “Instead of expecting one solution to work for everyone, it might be better to consider a variety of factors, including someone’s genotype, gut microbiome, gender and age,” said Ai-Ling Lin, a professor in the University of Missouri School of Medicine. “Since the symptoms of Alzheimer’s, which tend to be irreversible once they start, usually appear after age 65, the time to be thinking about preserving brain health is well before then. So hopefully our research can offer hope to many people through early interventions.”
Creating a Personalized High Fat Diet for Brain Health
On the topic of precision nutrition, keep in mind that a ketogenic diet is very restrictive, unfit for people with certain medical conditions, and certainly not the only way to consume more healthy fats. Neurologist Dr.Bryan Neth, who has studied the effect of diet on Alzheimer’s, eats more similarly to the Mediterranean diet. As a parent, it can be challenging to make healthy meals with little kids, so Neth focuses more on whole foods and fresh produce rather than ultra-processed foods. The Mediterranean diet tends to involve olive oil, fish, nuts, avocados, and seeds that are high in healthy fats. Some people have been taught to avoid these kinds of foods.
“...Good quality fats are absolutely fundamental for brain health and health of the cardiovascular system,” said Dr. Neth in an episode of Mayo Clinic’s podcast On Nutrition. “…It’s important to have the good quality fats that make up the cell membranes in the brain to have good brain health…” He added that these healthy fatty foods can contain micronutrients like vitamin E and Omega-3s, which also contribute to good brain health.
Although eating healthily is currently not proven to prevent Alzheimer’s, it can help people feel better and think better within a short period of time. So here are some high-fat foods to incorporate into a brain-healthy diet:
- Olives
- Olive oil and vegetable oils like sesame, walnut, and canola
- Walnuts
- Pistachios
- Almonds
- Pine nuts
- Pecans
- Brazil nuts
- Peanuts
- Flax seeds
- Chia seeds
- Soybeans
- Avocados
- Fatty fish such as tuna, cod, salmon, herring, sardines, and whitefish
- Dark chocolate
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