Maybe you are familiar with the incredible brain benefits of intermittent fasting, fasting, and calorie restriction, but you are still wondering how/why the hell not eating can be so beneficial for health.
Based on my research there are two credible explanations for how this became beneficial:
Explanation 1- Fasting as a survival mechanism
If we imagine our primal ancestors during the times of woolly mammoths and saber tooth tigers, they were often forced to go long periods of time without food. Probably many hours a day, or even several days at a time. But these early humans still needed energy for muscle, brain, and organs throughout the body. They needed energy to hunt, find food, and ultimately survive. Therefore, it is likely that these fasting mechanisms evolved in order to 1) provide energy in the absence of food (particularly energy for the brain), 2) strengthen the human so that it can survive the food shortage and be better able to deal with those challenges in the future. Those who developed the best “survival mechanisms” would have survived and passed along these traits. Obviously, this does not happen over night and would have evolved over thousands and millions of years. Indeed, the phrase “that which does not kill me makes me stronger” is synonymous with fasting.
Explanation 2- Fasting is Synonymous with Sleep
We can all agree that the purpose of sleep is to repair and recover. So what if fasting is simply meant to happen alongside sleep as part of this repair mechanism? This makes sense when we consider that many of the repair processes during sleep are prevented by food consumption immediately before bed. For instance, eating carbohydrates right before bed can inhibit secretion of human growth hormone (HGH) from our pineal gland. HGH is intended to repair muscle, bones, and connective tissue (among other things) throughout our body. So all these benefits of fasting would happened during sleep IF we are indeed fasted, and then these benefits simply continue a little longer if we wake up and do not immediately break our fast.
Regardless of which theory you believe in, the health benefits of fasting are profound. Perhaps the most fascinating one is the ability of fasting to stimulate neurogenesis and plasticity in the brain.
Synaptic plasticity is the ability of the brain to change its structure and function based on our experiences. It’s the reason you can learn a new skill at 9 years old and 90 years old. But this only happens if the brain has the proper resources to do so, and fasting provides these resources.
We can’t technically identify synaptic plasticity in humans, but animal studies (including monkeys) shows that energy restriction (caloric restriction) increases synaptic plasticity.
Human findings correlate this since energy restriction (‘ER’ for short) preserves brain function in old age and improves memory and learning.
Neurogenesis is a process whereby stem cells in the brain form functioning neurons, which can then form connections with existing neurons.
Until less than 20 years ago, neuroscientists believed it wasn’t even possible to grow new neurons. Until it was shown that exercise may be able to trigger this. Now it has been shown that fasting may also trigger it. Out of all the fancy gadgets and technology these days, its two ancestral practices – food restriction and exercise – that may have the most benefit for your brain. This cannot be replicated with a pill folks.
Indeed, ER and fasting can enhance neurogenesis by mechanisms involving upregulation of the expression of trophic factors including brain-derived neurotrophic factor (BDNF), insulin-like growth factors 1 (IGF-1), and vascular endothelial cell growth factor (VEGF). This is an epigenetic mechanism, because life conditions (fasting) are leading to genetic changes (e.g. up regulation of BDNF). BDNF is like fertilizer for our brain cells; it protects the brain from neurodegenerative disease like Alzheimer’s or concussions, but is also crucial for learning and developing new skills. VEGF is responsible for promoting new blood vessels, leading to enhanced blood flow to the brain. This is a great thing, enhanced blood flow means more energy and nutrients, and improved cleanup of cellular waste and toxicity in the brain.
It should come as no surprise then that more studies which use fasting or ER (energy restriction) show remarkable improvements to brain function, even in the elderly. For instance, when the caloric intake of fifty normal elderly subjects was reduced by 30% for 3 months, the performance on memory tests improved significantly compared to two different control diet groups. BDNF is likely involved in these cognitive improvements. Looks like breakfast isn’t the most important meal after all.
Auriel A. Willette et al., “Calorie Restriction Reduces the Influence of Glucoregulatory Dysfunction on Regional Brain Volume in Aged Rhesus Monkeys,” Diabetes 61, no. 5 (May 1, 2012): 1036–42, https://doi.org/10.2337/db11-1187.
Tytus Murphy, Gisele Pereira Dias, and Sandrine Thuret, “Effects of Diet on Brain Plasticity in Animal and Human Studies: Mind the Gap,” Neural Plasticity 2014 (2014), https://doi.org/10.1155/2014/563160.
A. Veronica Witte et al., “Effects of Resveratrol on Memory Performance, Hippocampal Functional Connectivity, and Glucose Metabolism in Healthy Older Adults,” Journal of Neuroscience 34, no. 23 (June 4, 2014): 7862–70, https://doi.org/10.1523/JNEUROSCI.0385-14.2014.
Abdolhossein Bastani, Sadegh Rajabi, and Fatemeh Kianimarkani, “The Effects of Fasting During Ramadan on the Concentration of Serotonin, Dopamine, Brain-Derived Neurotrophic Factor and Nerve Growth Factor,” Neurology International 9, no. 2 (June 23, 2017), https://doi.org/10.4081/ni.2017.7043.