Intermittent Fasting

Have you ever wondered why we eat 3 meals a day? And snacks in between? Most of us probably haven’t considered this, just accepted it… it is dogmatically ingrained in our society, and many western civilizations. But is it important? Is it biologically optimal? Is it GOOD for us? How do our bodies function when we follow this pattern? And how do they do when we DON’T follow this culturally-prescribed pattern of eating?

According to Abigail Carroll, and other historians this pattern of eating is a relatively new phenomenon, evolutionarily speaking. Ancient Romans ate one meal per day and considered eating more than this to be gluttonous. Ancient civilizations didn’t have sophisticated food storage technologies, and drive-through eating options, nor did they have food science that focused on ways to make the foods we eat trigger reward feedback pathways to keep us eating beyond the point of satiety. They lived under conditions of intermittent scarcity, with periods of time occurring when food was in short, very limited supply. Eating one meal per day, or eating smaller portions of food, as encountered, ‘foraging’ of sorts was the only option and our genes are actually designed with mechanisms to promote better health, when we do not eat excessively. Eating 3 meals per day, with additional snacks in between those meals, is excessive. The eating of an early morning meal shortly after rising (eventually termed ‘breakfast’ – to signify the ending or breaking of an overnight fasting period) became a ritual around the 17th century. Indigenous peoples of the new world did not follow these patterns. When European settlers arrived in North America, they viewed the native Americans as primitive and uncivilized with their foraging habits and unscheduled eating patterns, and the belief that those eating habits made native peoples ‘uncivilized’ further codified the belief in the superiority of eating 3 formal meals per day.

But, is it better? And what would better mean? It would be difficult for anyone to successfully argue, from a health standpoint, that the changes that have been made in agriculture over the past 80 years combined with the changes in how and what we eat, have been a net positive. At least not when it comes to our health.

Fast forward from the 18th century to today. Along the way, we have been dogmatically fed misinformation about when we should eat and the types of food we should eat, including being told for over a decade that an optimal food consumption pattern should include 6-12 servings of ‘grains’ – where the term grain was synonymous with refined, processed carbohydrates – (often with “research” sponsored by the grain and sugar industries) – and combined flawed or biased recommendations with a complete absence of education about nutrition, and the results are in. Soaring rates of chronic diseases like diabetes, high blood pressure, cancers, neurodegenerative disorders, and autoimmunity.

Without question, the way that we eat, as a society has been a significant contributor to all of these health consequences. Today I want to spend some time taking a look at one healthier option for eating patterns that has a lot of science showing how and look at some of the reasons why it is a much better health option for most, if not everyone.

It’s called intermittent fasting. (IF)

IF is a pattern of eating that has been shown to have a plethora of benefits on many aspects of our health. Not only does it tend to promote weight loss, and to decrease the production of free radicals in our bodies, it turns on evolutionarily conserved adaptive cellular responses – in our organs; it improves glucose regulation, increases our resistance to stress and it suppresses inflammation. During periods of fasting (exceeding at least 8, and more likely 12+ hours) cellular responses that promote repair work and the programmed cell-death of sick or non-functioning cells, including tumor cells occurs much more effectively.

IF shows benefit on conditions including: diabetes, cardiovascular disease, cancers, neurodegenerative brain disorders, and obesity, also in asthma, and other inflammatory and autoimmune conditions.  Scientists have gone so far as to say (with research to substantiate) that it slows or reverses aging. And therein, lies my fascination with intermittent fasting.

What is ‘intermittent fasting’ and how is it achieved? The three best studied forms of intermittent fasting are 

  1. alternate day fasting: 
  2. 5:2 intermittent fasting (though some advocate a 4:3 schedule of fasting, and
  3. daily time-restricted feeding.

These have different eating limitations, but have in common reduction of kcal intake (energy consumption) during the proscribed fasting interval and a resultant switch in metabolic pathways from glucose-consumption, to production and utilization of ketone bodies and fatty acids for the energy needs of the body. Ketone body production is a very important part of the health benefits of IF, as ketone bodies are not only a utilizable fuel source, they are more importantly, very powerful signaling molecules that have major, beneficial effects on cellular and organ functions.

  1. Alternate day fasting describes a variation of IF wherein one eats a healthy, appropriate amount of kcal on either 4 out of 7 days of the week, and consumes a restricted amount of total kcal on the alternating 3 days of the week. For men, typically 600kcal are consumed, and for women typically 500kcal on the “fasting” days. Some studies have shown that patients undertaking an alternate day fasting (4 days off and 3 days on) can lose 10-15 pounds in 3 months. Though weight loss is not the ultimate end point that I am placing emphasis on for the purposes of this discussion.
  2. A 5:2 regimen of IF incorporates 2 days of fasting, with 5 of the 7 days of the week having no restrictions. The two ‘fasting days must not be consecutive. 
  3. Daily time-restricted feeding involves eating during a set number of hours per day, typically being 8 hours of eating and 16 hours of fasting (called ‘leangains’) or, more strictly 4 hours of an eating window and 20 hours of fasting (called ‘warrior diet’ and typically the eating is done at the evening meal, or dinner).

The reasons why IF are so important and so beneficial, have to do with our evolutionary history and the fact that as we evolved, there were periods of starvation that were inevitable and our ability to survive and perpetuate despite those periods of scarcity – required alternative mechanisms of survival. The adaptations that our bodies utilized then, still exist, but are rarely required now, in our time of caloric abundance, and more so – in a time of nutritionally-deficient caloric abundance. In other words, we live in a time of cheap, easily, readily available foods, that offer minimal nutrition. Empty calories, comprise an abundance of the standard American diet (SAD).

When we abstain from eating, our bodies will gradually use up our glucose that is in our bloodstreams after the last meal we consumed. Once those glucose supplies are depleted (within a few hours after a meal), our bodies begin to access other sources of glucose- specifically those stores in the liver, and utilizes glucose produced by the liver, at around 12 hours of fasting, our bodies have utilized the glycogen reserves of the liver and – in the absence of new sources of glucose, our metabolism seeks out another source of fuel for our cells; that source, is fatty acids, triglycerides, stored in our bodies as fat cells. Triglycerides are broken down into free fatty acids and glycerol; then the FFAs are transported to the liver which converts them into ketone bodies; which are released into the blood, and circulated throughout the body. These ketone bodies can be utilized as a cellular source of energy, by all cells including neurons. A state of ketosis “flips” a metabolic switch in our cells, which has effects upon cellular responses, that are known to decrease inflammation and inflammatory markers; they regulate the expression and activity of proteins and molecules that are known to positively influence health and aging. Intermittent fasting also shows benefits across many health parameters.

If IF sounds difficult or intimidating, don’t worry. It doesn’t have to be, and there are ways to ease into it. But when you consider the health benefits, hopefully it will seem worth the effort, and more importantly, worth the benefits. 

Let’s look at the benefits!

Heart Health 

IF improves indicators of CV disease in animals and humans including blood pressure, resting heart rate, HDL, LDL, triglycerides, insulin and insulin-resistance. 

CVD is the number one killer of Americans both men and women. Atherosclerosis, or plaque-build up in the vessels is the leading cause of vascular disease. The reasons why it develops are myriad, and it is a multi-step process, and I will not go through the details of it here, as it is fairly complex, but there are inflammatory markers that are produced and that reflect various steps in the process. Many of these are positively affected when IF is implemented. IL-6, homocysteine, adiponectin, CRP, and leptin levels are a handful of the markers, that are found to be affected positively/beneificially when one follows intermittent fasting. 

Blood pressure.

IF has a beneficial effect on lowering blood pressure. Studies in the USA and out of Germany both showed a decrease in systolic and diastolic blood pressure, accompanied by a slight reduction in resting heart rate. Both of these are beneficial for heart health.

Cholesterol measurements.

IF improves measurements of LDL, HDL, oxLDL, triglycerides, glucose levels, and insulin and insulin-resistance. All of which have important positive effects on decreasing the chance of developing heart disease.

Brain Health

Brain health and cognitive function have been studied in both humans and animals who practice IF. In animal studies that looked at cognitive function, IF enhanced multiple measurements – including: spatial memory, associative memory, and working memory. A study that looked at older adults with mild cognitive impairment, a 1 year program of caloric restriction showed improvements in verbal memory, executive function and global cognition. Given the epidemic of dementias and the aging population, combined with the lack of any effective pharmaceutical interventions, it would seem that calorie restricting diets offer a promising, easy intervention to implement, though much more study is needed. Preclinical evidence shows that ADF can delay the onset and progression of animal models of both Parkinson’s disease nd Alzheimer’s disease. At the molecular level, IF and CR diets bolster mitochondrial function, BDNF production, autophagy, and antioxidant defenses. 


It is believed that IF impairs energy metabolism in cancer cells and inhibits their growth, and leaves them more susceptible to clinical treatment regimens. Trials are currently ongoing looking at effects of IF on patients with breast, ovarian, prostate, endometrial and colorectal cancers as well as glioblastoma. 

Asthma. MS. And Arthritis. Have all shown improvements in patients who practice IF. The precise mechanisms are not completely understood, but it is known that b-hydroxy-butyrate (a ketone body produced in the state of intermittent fasting… and also produced by the phyla of the microbiome that are nourished by plant-based diets) has a beneficial effect on decreasing inflammation in the lungs. One study that looked at patients who adhered to an alternate day fasting regimen found that over a 2-month period, participants noted decreased asthma symptoms and decreased airway resistance.  Multiple sclerosis shows improvement as well. Mouse models of MS found that the nerve demyelination (that is seen in MS) was reduced when alternate day fasting and energy-restriction was imposed on the mouse models. 

There are so many things that go into being healthy and more importantly perhaps, into wellness. For most people, they feel pretty good regardless of the food choices we make, and getting inadequate sleep and not enough exercise, for years, even decades. For most of us, there will come a point in time, when all of the sudden: nothing ‘changes’, but everything changes. When the same poor dietary choices, and lack of sleep, and absence of any stress-coping mechanisms ‘all of the sudden’ leaves them feeling really poorly. 

There are lots of tests that can be run, lots of money to be spent, and lots of supplements to take and hormones to try, and sometimes people get some degree of relief. But when we are pursuing true wellness, the foundation is always the same: eat better, sleep adequately, and move regularly. Everything else is fine-tuning. Amongst all of the diet-fads that exist, if you are looking to improve your health in areas that include: brain health, heart health, energy and performance, longevity, and lowered inflammation, intermittent fasting has more scientific support and rational than many options. When done properly it may be the most important part of wellness that we incorporate into our daily lives.

In good health,

Dr. Wendy

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