Benefits of Intermittent Fasting for Your Brain and Body

Benefits of Intermittent Fasting for Your Brain and Body
By Team Perlmutter
Category: Food

With all of the hype around fasting, you may believe it to be just another modern dietary fad, but the truth is that fasting is as old as our species. Until very recently, humans have always had periods of going without food. Fasting is baked into our evolution and our physiology and it can yield benefits to our brains and bodies, at a biochemical level, that we’re only just beginning to understand.

Many of us are blessed to live in a world with abundant food, but that wasn’t always the case. Throughout our evolutionary history, sometimes days, weeks, and months would pass during which food resources were scarce. These periods without food provided small hormetic stresses on our genome — meaning stresses that turn out to be beneficial to our bodies. In the absence of calories, life-sustaining, protective genes responsible for cellular repair and protection are activated, inflammation is reduced, and anti-oxidative defenses are increased.

This means that simply going without food for a while may have anti-aging, anti-inflammatory, and anti-tumor benefits that are available to anyone, at any time.

Fasting basics

Readers of my book Grain Brain know that the first step I recommend in the Grain Brain diet is a 24- to 48-hour water fast (with the important caveat that you should check with your physician first). This can be as simple as eating normally on a Sunday, finishing dinner by 6 PM, and drinking only water until 6 PM on Monday when you can enjoy a nice meal again. I recommend doing a 24- to 48-hour fast at least four times a year, though some enjoy doing a 24-hour fast as often as twice each week.

One of the most obvious and immediate benefits of fasting is psychological — the opportunity to conquer a fear of hunger. We’ve been indoctrinated to avoid hunger at all costs, fearing a blood-sugar crash or the feeling of being “hangry.” Fasting gives you the chance to push through the discomfort of mild hunger to discover the clarity and freedom on the other side. It can reinvigorate your whole relationship with food and give you a greater sense of balance, control, and enjoyment.

Fasting’s Effect on the Body

When our bodies fast, we begin to mobilize glycogen from the liver and the muscles. When our glycogen stores are depleted, our metabolism shifts and we start to mobilize fat and use it to create ketones, a source of energy that powers the brain in a different way, helping it to function more efficiently. Beta-HBA, the principal ketone, has been shown to be a super-fuel that produces ATP energy more efficiently than glucose.

Not only does Beta-HBA protect neuronal cells from toxins associated with Alzheimer’s and Parkinson’s, it also improves antioxidant function, increases the number of mitochondria, and stimulates the growth of new brain cells.

Daily Caloric Restriction vs. Fasting

Caloric restriction is one way to spur production of this valuable ketone, but many people find reducing daily caloric intake too tough to adhere to long-term. The good news is that intermittent fasting — restricting food intake for anywhere from 24- to 72-hours — is another effective way of increasing production of beta-HBA, and many people find it much more manageable and sustainable than daily caloric restriction.

Fasting can help us reap many of the benefits of caloric restriction in a way that allows us to eat normally for a majority of the time. In addition to increasing beta-HBA, fasting also activates the Nrf2 gene pathway that aids detoxification, decreases inflammation, and stimulates mitochondrial growth. When the body is in a fasted state, even the process of apoptosis (or programmed cell death) is refined, eliminating damaged cells that can lead to the development of cancer.

Does Fasting Slow Metabolism?

Even with all these important benefits, some may be reluctant to try fasting due to the outdated belief that it lowers metabolism and forces the body into starvation mode, causing it to hang on to fat. But in fact, the opposite is true. A regular schedule of intermittent fasting can actually accelerate and enhance weight loss. According to a recent review of 40 independent studies, intermittent fasters lost an average of 7-11 pounds over the course of ten weeks.

Supercharge your Brain

Another benefit of fasting is the stimulation of BDNF, a protein that plays an integral role in stimulating the growth of new brain cells and the performance of existing neurons. BDNF is best described as the brain’s “growth hormone,” and stimulating its production is easily one of the best things you can do for your body and your brain.

To recap, some of the many benefits of fasting include:

  • Enhancing the same beneficial genetic pathways that are activated by caloric restriction, with a fraction of the difficulty
  • Stimulating the production of BDNF, the brain’s growth hormone, which also supports the function of existing neurons
  • Stimulating mitochondrial replication
  • Accelerating weight loss (when done on a regular schedule)
  • Decreasing inflammation
  • Enhancing protection from diseases including Alzheimer’s, Parkinson’s, and cancer
  • Improving antioxidant function
  • Increasing production of beta-HBA, a super-fuel for the brain and body

But again, it’s important that you consult your physician before integrating fasting into your life. It may be contraindicated for those who are insulin-dependent diabetic, have a history of eating disorders, or suffer from ulcers. If your doctor gives you the green light, here’s the protocol I recommend.

How to Fast

Try a 24-hour fast to start. As you get more comfortable with it, and your body becomes more efficient at using fat for fuel, you can experiment with occasional fasts of 48- or even 72-hours. But for now, choose one day that you want to spend fasting. Some prefer a Sunday, others like to fast on a workday when they can stay busy and distracted.

If you opt to fast on a Monday, finish your dinner on Sunday by around 6 PM, then stop consuming all calories. Nothing should pass your lips except water or some herbal tea.

Stay well-hydrated throughout the day, and notice how you feel. Hunger may start to roll in in waves by late morning, but notice how it always eventually subsides. Do you notice any more mental clarity than usual? Rest assured, your body will use its ample reserves of glycogen and fat to provide you with the fuel and energy you need.

By 6 PM on Monday, you’re all done! Treat yourself to a healthy and nutritious meal. Take the opportunity to savor each bite and notice how delicious it tastes.

Your body and brain will thank you.

Want to learn more about the ketogenic diet? Then consider checking out my e-guide to this incredibly powerful dietary and lifestyle choice.

Related Topics

Fasting  BDNF  Metabolism  Inflammation  

Share This


Dr. Perlmutter is one of the leading lights in medicine today, illuminating the path for solving chronic illness

Mark Hyman, MD