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Intermittent Fasting & Cognition: Change When You Eat to Boost Your Brain

Feb 04, 2023

Is fasting just the latest health craze, or can it really make a difference in our health? Let’s examine the science behind fasting and how it impacts our brains.

Our day-to-day lives are incredibly different than they were in decades prior. As technology expands and we become a more global society, we often find ourselves staying up later. And as many people watch TV, play video games, or chat with a friend in another time zone late into the night, they may find themselves doing something else, too: eating. (The phrase “midnight snack” exists for a reason, right?)

Not only do we find ourselves staying awake longer, we’re doing so when food is more widely and readily available to us than ever. Whether you’re digging through your fridge at 10pm, ordering take-out from your favorite late-night spot, or hitting up a 24-hour corner store, there are more and more opportunities for us to spend more and more hours of the day eating. But around-the-clock consumption isn’t the healthiest choice to get our daily nutrition.

What is intermittent fasting?

Most diet and nutrition plans function by telling you what to eat. But fasting is about when you eat - and when you don’t eat. Essentially, fasting is a dedicated period of time during which you choose not to eat. Intermittent fasting refers to developing an ongoing pattern of cycling through periods of eating and fasting.

What doesn’t count as intermittent fasting?

While there are several different ways to create and follow an intermittent fasting plan, there’s one major caveat to keep in mind. In order for your body and brain to capitalize on the health benefits of intermittent fasting, the time spent fasting must include some of your waking hours. In other words, taking a break from eating every night while you’re asleep doesn’t count! Your fasting period may include the time you spend asleep, but eating immediately before bed or right after waking up isn’t generally recommended by intermittent fasting plans.

How does intermittent fasting work?

Though its recent popularity in health and fitness spheres may lead you to think intermittent fasting is just the latest health craze, the practice of fasting dates back centuries. People and cultures around the world have engaged in fasting for spiritual and health purposes. But how and why does fasting actually work? Let’s take a look at the science behind eating, and how fasting affects our bodies and brains.

Promoting metabolic switching

When our bodies digest the food we eat, they break down the carbohydrate components (sugars and starches) into a type of sugar called glucose. This glucose is released into our bloodstream, where it can be used immediately for energy to keep us awake, alert, and functioning. Energy we don’t use immediately gets stored for future use; some as glucose, and the rest as fat. Once we stop eating, our bodies rely on this stored energy to sustain themselves.

Going short periods without food means our bodies only need to exhaust the energy stored as glucose. However, the longer we go between meals, the more of this stored energy gets used up. Eventually, the body will run out of glucose energy, and instead begin burning fat for energy. This process is referred to as metabolic switching.

When a person engages in intermittent fasting, they prolong the period of time between meals. This encourages metabolic switching and leads the body to burn fat.

Entering ketosis

Following this metabolic shift, our bodies enter ketosis. Ketosis is the metabolic state during which our bodies burn fat for energy. It’s named after ketones, the compounds formed when our bodies’ fat stores break down. Essentially, the longer you fast, the more ketones your body produces. Ketosis reduces the amount of glucose used by the brain, which research has shown may help improve neurological conditions, such as Alzheimer’s disease. 

Encouraging cellular autophagy

Every tissue and organ in our bodies is made up of cells, and each cell is made up of multiple parts that keep it functioning properly. Over time, these cell parts can become worn down, defective, or even stop working entirely. Luckily, our bodies know exactly how to handle this: they disassemble, salvage, and reassemble the working parts into new cells. This process is called autophagy.

Autophagy is essential to keep our cells (and our organs, and our bodies) functioning properly. It gets rid of nonfunctional “junk” cell parts, optimizes cell performance, and even helps destroy pathogens like viruses and bacteria. 

The process occurs naturally, but you can also induce autophagy by adding stress to your cells, sending them into “survival mode.” One of the simplest ways to induce autophagy is to fast. When your body doesn’t have a constant stream of nutrients from eating, you essentially force it to repurpose existing cells to function.

Using fasting to take control of your body & health

Choosing to incorporate intermittent fasting into your life is about more than choosing when and when not to have a meal. The goal isn’t just to have better control over your eating habits, but to have better control over how your body processes and reacts to the nutrition you provide it. Intermittent fasting can help foster metabolic flexibility, allowing you to take control of your body’s ability to burn either glucose or fat for energy. It will also let you promote cellular autophagy - essentially setting up a regular “housekeeping” schedule for your cells.

But what do these internal benefits mean for you? Let’s look at how intermittent fasting can impact our health.

Health benefits of fasting

Periods of fasting can influence your metabolism, how your body burns energy, and how frequently your cells recycle themselves to boost performance. Here are some of the health benefits that you can experience from intermittent fasting.

Weight loss

Weight loss is one of the most popular reasons people try intermittent fasting. Because fasting generally works by reducing the amount of food you eat, the reduced caloric intake can help you lose weight. However, it’s important to remember that fasting alone can’t make you lose weight in a sustainable and healthy way. You still need to follow a proper balanced nutrition plan during your eating cycles. (For most people, this means focusing on non-starchy vegetables, protein, and healthy fats.)

Heart health

Several studies indicate that intermittent fasting can help reduce blood pressure and cholesterol levels in adults, as well as improve resting heart rates. So, fasting can contribute to a decreased risk for heart disease and better heart health overall. 

Improved cognitive performance

Though further study is needed, research examining intermittent fasting determined it boosted both brain structure and cognitive performance in mice. Specifically, fasting may help improve our working memory and our verbal memory. Other studies indicate that the autophagy encouraged by fasting can help promote better brain health, thanks to increased regeneration of nerve cells.

In addition, fasting can contribute to several different ways to counter cognitive decline, including creating insulin sensitivity, reducing inflammation, increasing circulation and optimizing blood pressure, and addressing mitochondrial and other cell deficiencies.

Decreased risk of neurodegenerative disorders

Beyond generally increasing your brain’s function and performance, intermittent fasting may also help decrease your risk for neurodegenerative disorders, such as Alzheimer’s disease and Parkinson’s disease. Over time, damaged DNA that builds up in our genome can lead to increased cell mutations that go unrepaired, leading to problems in our cognitive function. When we fast, our brain cells begin to conserve resources and increase autophagy, leading to the formation of new synapses and neural pathways. These new networks in our brains can help stave off neurodegenerative disorders.

Fasting FAQs

Here are a few more common questions you may have about fasting.

What can I eat while fasting?

During fasting periods, you should continue to stay hydrated by drinking plenty of water. You may also opt to consume zero-calorie beverages like black coffee and tea. Fasting in general doesn’t dictate what you can and can’t eat when your fast ends. However, if you want to experience the full health benefits of fasting, you should avoid binge-eating and junk foods, and focus on consuming a balanced diet of proteins, leafy greens, and healthy fats.

How long should I fast?

There are several different approaches for how to construct an intermittent fasting plan. However, most people will opt to fast for between 12 and 16 hours a day. This leaves a window of 8-12 hours during which you can eat each day. You may want to start with a 12/12 fasting/eating cycle and then increase your fasting hours over time.

Can I fast for longer periods of time?

Prolonged fasting - aka fasting for 48 hours or more - can also have health benefits, such as encouraging autophagy, enhancing stem cell production, and increasing our cells' resistance to stress. However, the longer you go without eating, the more your body will need to adjust. Consult your doctor for more information about safely and effectively extending your fasting period.

What are the side effects of fasting?

Side effects of fasting can include hunger, fatigue, irritability, insomnia, constipation, and headaches. However, these symptoms generally disappear over time as your body gets accustomed to your new eating schedule. Most people report the side effects of fasting disappear after about a month. If fasting leaves you feeling sick or dizzy, like you might pass out, you may need to adjust your diet to safely maintain your blood sugar levels. Low blood sugar levels can be caused by a number of factors, including not enough healthy fats and too many carbohydrates and unhealthy sugars in your diet. Again, talk to your doctor if you experience any severe symptoms after beginning a fasting regimen. 

Is intermittent fasting right for me?

Intermittent fasting is safe for most adults; however, no one diet or nutrition plan works the same for every person. It’s also important to note that fasting may be unhealthy or unsafe for certain individuals, such as:

  • Children and teens under 18
  • People with diabetes
  • People with or recovering from eating disorders, such as anorexia or bulimia
  • People currently taking medications that require a food intake
  • People who are underweight

Remember to always discuss any significant changes in your diet and eating habits with your doctor. 

More nutrition tips to feed your brain

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