Intermittent fasting is an eating pattern where you switch between periods of eating and fasting. Fasting typically involves eating no food at all, but in some approaches, it means eating a reduced number of calories.
Scientists have only recently begun to look closely at the relationship between intermittent fasting and brain health. However, there’s already some evidence that it may have certain cognitive benefits as we get older, as well as reduce symptoms of mental health conditions like anxiety and depression.
Restricting your food intake may also increase your ability to produce new brain cells, which could improve some aspects of memory.
If you try intermittent fasting, it’s important to choose the right foods between fasts.
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Read on for more information about the links between intermittent fasting and brain health, and to learn about the best foods to support your overall health.
What is intermittent fasting?
Intermittent fasting is an approach to eating that involves switching between periods when you don’t consume any calories and periods when you eat as usual — or when you limit the amount you can eat on certain days.
Intermittent fasting goes back thousands of years and is a part of many cultures and religions. Researchers have studied its use for weight loss since the early 20th century and have looked at its other potential health benefits more recently.
There are three common approaches to intermittent fasting:
Time-restricted eating: This involves a window of time when you eat as usual and another when you fast. The most common method is 16/8, with an 8-hour period when you can eat and 16 hours (including while you’re asleep) when you don’t eat. Consuming any calories will, in theory, break your fast. There are also 14/10 and 20/4 versions of this.
Alternate-day fasting: With this method, you switch between days with a normal eating routine and days when you eat very little. Some people follow a modified version that allows around 500 calories, either as a small meal or spread throughout the day.
5:2 fasting: Rather than alternating days, you select 2 days a week when you limit your calories to around 500–800 a day.
Fasting and brain health
Scientists have conducted only a limited amount of clinical research into how intermittent fasting may affect brain health. However, large-scale studies based around religious fasting show encouraging results when it comes to brain function during aging and mental health conditions.
Brain function during aging
There is some evidence that intermittent fasting may help to improve certain aspects of brain function as we get older, such as mild cognitive impairment (MCI). MCI is a stage that comes before dementia. It includes problems with memory or thinking and is known to be reversible.
One study involved three groups of people aged 60 and above with mild cognitive impairment. One group followed intermittent fasting twice a week from sunrise to sunset as part of their religious practices. Another group did so less often, while a third group did not fast at all.
A follow-up 3 years after the study began found that almost 25% of people in the regular fasting group now had no cognitive impairment, compared with 14% in the occasional fasting group and less than 4% in the non-fasting group.
People in the group who regularly followed intermittent fasting also performed better at cognitive tasks.
The regular fasters lost more weight and improved their metabolic profiles, and had different social factors than the other participants, so it’s hard to say for sure what was behind the improvements to brain function.
However, researchers found that the participants who regularly fasted had higher levels of an enzyme that may protect against cell damage. They also showed increases in ketones, the fuel that your body burns from fat stores during periods of fasting.
Further research is needed to find out whether these substances are involved in the potential link between intermittent fasting and improvements in brain function as we age.
A number of studies have looked at the impact that intermittent fasting might have on mental health issues, including stress, anxiety, and depression.
A recent scientific review analyzed 11 of these studies, with a total of over 1,400 participants.
Most studies were based on fasting between dawn and sunset during the Islamic holy month of Ramadan. Others involved 5:2 and 1-day-a-week fasts, as well as 14/10 time-restricted eating.
The scientists found that fasting during Ramadan was associated with improvements in stress, anxiety, and symptoms of depression.
When taken together, the studies for other forms of intermittent fasting didn’t produce significant results. However, when poorer quality research was removed, the remaining studies showed that participants had lower levels of anxiety and depression after following intermittent fasting.
While these are promising results, what scientists don’t currently know is exactly how fasting and improvements in mental health are linked and whether this is related specifically to the way intermittent fasting works or simply due to eating fewer calories.
Studies involving rodents have shown that intermittent fasting increases the animals’ ability to produce new brain cells, a process known as hippocampal neurogenesis. This process is important when it comes to certain aspects of memory, so scientists have begun to follow it up with research involving people.
In one small study, volunteers aged 35–75 with overweight followed either intermittent fasting or a standard calorie-restricted diet for 4 weeks.
The results showed improvements in both groups for a process called pattern separation, which helps your brain to distinguish between similar memories. However, when it came to recognition memory, people in the intermittent fasting group actually showed worse ability afterward.
The researchers concluded that eating fewer calories might help improve types of memory that are based on hippocampal neurogenesis. However, there was no evidence to suggest that this has to do with the specific way intermittent fasting works.
What to eat while intermittent fasting
Intermittent fasting means going for longer than usual without eating, or limiting the calories you consume. So, it’s important to make sure that when you do eat, you’re getting a healthy diet that can support you through the fasting periods.
Eating a wide range of plants will feed the “good” bacteria that live in your gut and help you to get the nutrients you need.
Sources of high-quality fiber and protein can also help you to feel fuller for longer.
Try to include:
legumes, like chickpeas and lentils
nuts and seeds, fish and poultry
There’s evidence that eating these types of foods — often included in the Mediterranean diet — may also help with your brain health.
One large-scale study, involving people with an average age of 70, found that sticking more closely to a Mediterranean diet was associated with a lower risk of cognitive problems.
Although there are some broad guidelines you can follow to improve your diet, everyone responds to food differently.
Choosing the right foods for your body can reduce your risk of chronic conditions like heart disease, stroke, and type 2 diabetes, and can improve your overall health.
With ZOE’s at-home test, you can measure your blood sugar and blood fat levels and get a snapshot of the different bugs that live in your gut.
Based on your unique results, the ZOE program gives you personalized nutrition advice to help you choose the best foods for your body.
People who closely followed their personalized ZOE nutrition plan for 3 months lost an average of 9.4 pounds in body weight, and over 80% said they had more energy and didn’t feel hungry.
You can take a free quiz to learn more about what ZOE can do for you.
Research into links between intermittent fasting and brain health is in its early stages.
However, there’s some evidence that eating in this way may help to improve some aspects of brain function as we age and reduce symptoms of mental health issues like anxiety and depression.
If you do try intermittent fasting, it’s important to eat a healthy diet in the periods between fasts to support your overall health and your brain health. The Mediterranean diet provides some broad guidelines for this.
However, ZOE’s research has shown that everyone responds differently to foods, and understanding your personal responses can help you choose the best foods for you.
Take our free quiz to learn more about how ZOE’s at-home test can help you.
Adherence to a Mediterranean diet and cognitive function in the Age-Related Eye Disease Studies 1 & 2. Alzheimer’s & Dementia. (2020). https://alz-journals.onlinelibrary.wiley.com/doi/abs/10.1002/alz.12077
Dietary protein — its role in satiety, energetics, weight loss and health. The British Journal of Nutrition. (2012). https://pubmed.ncbi.nlm.nih.gov/23107521/
Energy restriction enhances adult hippocampal neurogenesis-associated memory after four weeks in an adult human population with central obesity; a randomized controlled trial. Nutrients. (2020). https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC7146388/
Fasting interventions for stress, anxiety and depressive symptoms: a systematic review and meta-analysis. Nutrients. (2021). https://www.mdpi.com/2072-6643/13/11/3947
Fiber up, slim down. (2018). https://www.heart.org/en/healthy-living/healthy-eating/losing-weight/fiber-up-slim-down
Intermittent fasting enhanced the cognitive function in older adults with mild cognitive impairment by inducing biochemical and metabolic changes: a 3-year progressive study. Nutrients. (2020). https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC7551340/
What is mild cognitive impairment? (2021). https://www.nia.nih.gov/health/what-mild-cognitive-impairment