Time Restricted Fasting

by Spencer ReedNutrition
Laughing women fasting

At this point, we’re all familiar with the idea that what we eat impacts our health. The burger, fries, and a chocolate shake western diet breeds chronic disease, while a diet rich in non-starchy vegetables, fruits, and other whole foods promotes wellness. We know that what we eat matters. But did you know that when you eat matters nearly as much?

Recently, time restricted fasting (TRF) has come to the forefront of nutrition research as a method to increase overall physical health, as well as prevent the onset of diseases later in life. This method consists of an approximately 12-hour period of eating followed by a 12-hour period of fasting. During the feeding period, people eat during the active part of their day, providing calories and energy to keep their bodies functioning properly. During the fasting period, usually occurring during the evening, people should restrict themselves from any food or drink intake besides water, allowing their bodies to focus energy elsewhere (1). In other words, you allow yourself to eat anytime in the 12 hour period. Outside of that 12 hour period, you don't eat. The number of calories consumed per day can remain around the same, just the frequency of and time allowed for eating is reduced (2).

We evolved to fluctuate through regular periods of feeding and fasting. Only recently have we had access to food literally 24 hours a day (the early humans didn't have UberEATS). So it makes sense that getting back in touch with this healthy rhythm of fasting and feeding would have health benefits. Below are some (definitely not all) of the more nuanced effects of TRF:

  1. TRF has been shown to promote cell autophagy, a process by which a cell degrades and recycles damaged proteins and other molecules. During periods of fasting, this process is upregulated—or more active than normal—and allows the body to cleanse itself of harmful substances, providing a protective role in cells. In the brain, the process of autophagy removes harmful materials from neurons, both protecting the neurons themselves from harm or death and improving the overall cognitive abilities of the brain (3).
  2. TRF helps reduce blood glucose (sugar) and insulin levels. High blood sugar affects millions of people worldwide and is a main symptom and cause of diabetes.  In addition, the hormone insulin plays a role in promoting cells to absorb glucose from the blood and minimizing inflammation, but too much insulin can cause a resistance to the hormone, reducing its effectiveness. Insulin resistance is one of the main causes of Type-II diabetes and plays a large role in the development of Alzheimer’s disease, so it’s important to keep blood glucose and insulin at an optimal level (4).
  3. TRF can serve to develop new neurons within the brain. Research has shown that dietary restrictions consisting of periods of fasting and periods of feeding enhanced neurogenesis—the creation of new neurons—in the brain (5). In addition, time restricted fasting also decreased the spontaneous death of newly-generated neurons within the brain, suggesting a positive role for TRF in the development and maintenance of brain cells (5).
  4. TRF plays a role in the inflammatory response of the body. Inflammation is our body’s response to attack by foreign or infectious molecules, serving a protective role. However, chronic inflammation can be detrimental for the body, particularly if the immune system goes overboard and targets healthy cells. Inflammation is one of the three main factors that contributes to Alzheimer’s disease (along with trophic withdrawal and toxic exposure). Research has shown that TRF can effectively reduce inflammatory processes (6).

So how does all this tie into Alzheimer’s disease?

Long story short, if you're concerned about the health of your brain, you should be practicing TRF.

In terms of autophagy, TRF allows the body time to recycle and degrade harmful proteins and other substances within neurons. Alzheimer’s is characterized by the loss and degradation of brain neurons, so any process that can help keep existing neurons functioning will decrease the cognitive decline associated with Alzheimer’s disease. Moreover, TRF was shown to increase neurogenesis and decrease the spontaneous death of newly-generated neurons, serving another role to promote the development and maintenance of neurons that could possibly be lost due to Alzheimer’s disease or cognitive decline.

In addition, Alzheimer’s disease is characterized as a protective response to three specific processes: inflammation, suboptimal levels of nutrients and other molecules, and toxic exposures (7). Regarding inflammation, the protective response of our bodies produces proteins called amyloids designed to fight off pathogens, yet these amyloids can go overboard and accumulate in neurons, destroying neuronal connections and leading to cell death. With this effect of inflammation in mind, TRF has been shown to reduce the inflammatory response in the body and thus help prevent and reverse Alzheimer’s disease.

Finally, insulin resistance is potentially the most significant single metabolic contributor to Alzheimer’s disease, its development, and its progression (7). Thus, it’s extremely important to prevent insulin resistance and allow the insulin to function as designed in the body. TRF has been shown to reduce blood glucose and insulin, inhibiting our bodies from developing insulin resistance.

It may take some time and effort to get accustomed to time restricted fasting into our hectic lives, but the overall health benefits remain clear. This one simple change to your daily routine will have a remarkable impact on your health, especially your brain health. Start practicing time restricted fasting today to start reaping the benefits!


1.) Chaix, A., Zarrinpa, A., Miu, P., Panda, S. (2014). Time-Restricted Feeding is a Preventative and Therapuetic Intervention against Diverse Nutritional Challenges. Cell Metabolism 20.6, 991-1005.

2.) Moro, T., Tinsley, G., Bianco, G., Pacelli, Q.F., Battaglia, G., Palma, A., Gentil. P., Neri, M., & Paoli, A. (2016). Effects of eight weeks of time-restricted fasting (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. Journal of Translational Medicine 14.290, 1-10.

3.) Alirezaei, M., Kemball, C.C., Flynn, C.T., Wood, M.R., Whitton, J.L., & Kiosses, W.B. (2010). Short-term fasting induces profound neuronal autophagy. Autophagy 6.6, 702-710.

4.) Barnosky, A.R., Hoddy, K.K., Unterman, T.G., & Varady, K.A. (2014). Intermittent fasting vs. daily calorie restrictions for Type-II diabetes prevention: a review of human findings. Translational Research 164.4, 302-311.

5.) Lee, J., Seroogy, K.B., & Mattson, M.P. (2002). Dietary restriction enhances neurotrophin expression and neurogenesis in the hippocampus of adult mice. Journal of Neurochemistry 80, 539-547.

6.) Faris, E.M., Kacimi, S., Al-Kurd, R.A., Fararjeh, M.A., Bustanji, Y.K., Mohammad, M.K., & Salem, M.L. (2012). Intermittent fasting during Ramadan attenuates proinflammatory cytokines and immune cells in healthy subjects. Nutrition Research 32.12, 947-955.

7.) Bredesen, D.E. The End of Alzheimer’s: The First Program to Prevent and Reverse Cognitive Decline. New York: Avery, 2017. Print.