Will a Fasting Diet Give You The Results You Want?
Fasting has come in and out of vogue for generations. One year, it is the best thing you can do for your body to reduce disease, increase health, and even life expectancy, while the next, we’re told it can lead to a lowered metabolism rate and long-term weight gain.
So, which is it, what does the scientific evidence teach us? The truth may surprise you. Before we check out the latest trends, and what published journal articles tell us–let’s take a look at the roots of this ancient practice.
In this article:
- Why Do People Fast?
- Dangerous Fasting Diets
- The Different Types of Fasting and Fasting Diets
- Stages of Fasting
- Benefits of Fasting
- You Don’t Have to Starve on a Fasting Diet
- The “Healing Crisis” That Isn’t
- Side Effects of Fasting
- Choose a Fasting Diet Wisely
- Who Should Not Fast?
Why Do People Fast?
Fasting has been used for both physical and spiritual rejuvenation for thousands of years. The great Greek scholars, Socrates and Plato, fasted in order to purify the mind and body.
Hippocrates, the father of Western medicine and the famous Hippocratic Oath, believed that eating when sick simply feeds the illness. Pythagoras required individuals to fast before becoming his students, and considered a 40-day fast necessary to access deep truths:
“…Through this purification, my center of being has changed. From the intellect it has come down to the heart. Now I can feel things…Now, truth is not a concept to me, but life.”
-Pythagoras, following his 40 days of fasting¹
Many religious groups encourage fasting, including Muslims, who fast from sunrise to sunset during the holy month of Ramadan; Roman Catholics, who observe a 2 to 40-day fast during lent; and Latter-day Saints (Mormons) who observe a “Fast Sunday” the first Sunday of each month.
You’ll notice that most of the reasons for fasting are to promote clarity, health, and spiritual alignment—not weight loss.
Should you fast to lose weight?
While weight loss is a natural byproduct of going a length of time with absolutely no food, and it is the #1 concern of most Americans today, I recommend fasting or detoxifying with the intention of cleansing every cell in your body and taming inflammation, not the intention of fitting into a smaller pant size. (There are easier ways to lose weight!)
Does fasting lower your metabolism?
Keep in mind, that belief I mentioned earlier–that fasting leads to a lowered metabolism rate and, ultimately, weight gain–is a myth, not a science-based fact. Every time you take a sip of your smoothie, juice, even water, your body converts the fuel into energy that your body then uses to power every activity–a process known as metabolism. The rate your body performs this function is based on several factors including your body size and muscle mass.²
The Different Types of Fasting and Fasting Diets
Fasting is, in essence, consuming very little to no food. This reduction in caloric intake can last anywhere from 12 hours to a month or more, depending on the protocol.
Water fasting is going without food, and drinking only water, for an extended period of time. This practice gives the body time to rest from the processes and energy normally devoted to digesting food, and allows it the opportunity to focus on burning up accumulated toxins and fat stores, repairing tissues, and renewing at a cellular level.
Keep in mind that it is useful to prepare for such a water fast by preceding it with one to two weeks of a cleansing diet (no processed food or animal products or stimulants), followed by a few days of fresh juices, before limiting yourself to just water for a period of days or weeks.
Preparing the body gradually in this way allows waste products to move through the various organs of elimination and not overload the body as they break down. The body will, given time, begin to consume everything that is not vital to daily functions such as viruses, bacteria, chemicals, and heavy metals, to name a few.
(It will even break down some muscle tissue, but only the tissue that needs to be replaced anyway–muscle must regenerate, too! The body does not consume healthy tissue first because it’s resistant and hard to break down.)
Juice fasting is similar to water fasting in that your digestive system is getting a needed break from solid foods. It differs from water fasting in that your body is getting a limited amount of energy from nutrient-dense fresh vegetable and fruit juices.
These nutrients help maintain the alkalinity of the body as well as your glucose and electrolyte balances. Because your body is getting some calories, autophagy (when the body begins digesting itself in search of energy) is not quite as pronounced the first few days. The wonderful part of autophagy is this: your intelligent, amazing body goes after diseased and weakened tissues first, because healthy tissue is resistant to breaking down.
Dry fasting is, as I see it, fasting at its extreme. In essence, it entails denying yourself both food and water. This type of fasting seems to be most often performed as a sacrifice or a show of faith. LDS (Mormon) adherents are instructed to avoid both food and water for 24 hours, on the first Sunday of each month, for instance.
Some doctors who lead fasting retreats claim that the “burn” in the body is exponentially increased, by a day or two of fasting with no water. I have not been able to find published scientific evidence to prove this, however.
But your body is still going through the detoxification process, only without the aid of water to carry away the toxins. If you feel compelled to undergo a dry fast, be sure to complete a detoxification process first, and I cannot see the value of doing it for more than a day at a time. Water is essential.
For those of you who are nervous about the thought of no food for days on end, you’ll be happy to hear that there are alternatives. These “modified fasts” allow food, under restricted conditions, claiming the benefits of fasting without being hungry. The following are types of modified fasting.
Modified Fasting: Fasting-Mimicking Diet (FMD)
Dr. Valter Longo, director of the Longevity Institute at USC and one of the world’s leading researchers in longevity, developed the newly popular Fasting-Mimicking Diet.
In his book, The Longevity Diet, he describes how his specially formulated plant-based protocol allows you to experience the full benefits of a five-day fast while still consuming pre-packaged snacks and meals that have been designed so that your body does not recognize the nutrients as food and therefore mimics a fasting state.4
[Related Vibe Podcast: Fasting for Longevity With Dr. Valter Longo]
This protocol allows you to reach a biological fasting state while still consuming food. We will cover the trials Longo and fellow researchers have conducted, later in this post, that suggest “fasting-mimicking” modified fast health benefits are possible from eating 600 to 800 calories a day, for a few days at a time.
Modified Fasting: Intermittent Fasting
Growing in popularity, this protocol involves lowering caloric intake for a few days a week. For instance, you would eat normally for five days and then consume less than 600 calories for two days.
I don’t actually consider this practice to be “fasting.” It’s really just “time-restricted eating,” and it’s a bizarre modern phenomenon that we must suggest to people that they stop grazing the entire 16 hours they are awake.
Since the dawn of man, people have eaten 2 or 3 meals a day, and have abstained for 12 to 16 hours.
“Intermittent fasting” is simply eating breakfast, lunch, and dinner (sometimes skipping one of these meals), and not eating in between.
Time-Restricted Eating (TRE)
This type of fasting diet is also gaining in popularity, and involves not eating for an extended period each day. The hours you abstain from food vary dramatically–anywhere from 12 to 20 hours.
It’s a strange modern American phenomenon, that people eat all day, every day. This is likely part of why we have unprecedented levels of health problems and obesity–it’s not just what we’re eating; it’s also how often and for how long.
So, “time-restricted eating” seems very basic to me, just getting us to recognize that the body needs 12 hours to rest from food–and perhaps doesn’t quite qualify as “fasting.”
The Stages of Fasting
It takes time for your body to go through the various fasting stages. After the first day or two, the body depletes its glycogen stores from the muscles and the liver—the stored carbohydrates that provide quick energy. It then begins consuming fat for its energy requirements as well as protein.
You’ve probably heard of the term “ketosis.” Ketosis is a metabolic state that occurs in this first stage, when your glucose levels are in short supply, which leads the liver to turn fat into ketones as an alternative fuel source.
In essence, you are burning up your fat for fuel. Fasting is a much better way to enter the state of ketosis than the popular low-carb, high-fat, ketogenic craze that has been debunked by numerous doctors and health researchers.
Once ketosis occurs, big changes begin, which includes autophagy—a process in which, due to limited nutrients, your cells begin to eat debris and eliminate waste in order to optimize their chances of survival.
As autophagy continues, the “survival of the fittest” becomes evident as old and damaged or defective cells begin to die off. At that point, stem cells that repair and replenish tissues shift from a dormant state to a state of self-renewal, rebuilding the system from the ground up—including the regeneration of new immune system cells.
The Benefits of Fasting, According to Studies
Studies show that when done correctly, fasting offers a wide array of benefits. These include the following:
Increases mental clarity and energy.
Clinicians have found that fasting, particularly between day two and seven, corresponds with an improvement in mood, an increase in alertness, and a sense of serenity.5
In a study conducted by Dr. Longo, mice that received a Fasting-Mimicking Diet for four-day cycles twice a month, starting in middle age, showed better short and long-term memory as well as increased learning abilities.3
Aids in cellular renewal and stem cell-based regeneration.
A study published in USC News showed that prolonged fasting “induced immune system regeneration, shifting stem cells from a dormant state to a state of self-renewal.”6
Dr. Longo and his team of researchers discovered that fasting for prolonged periods (going without food for periods of two to four days at a time) broke down a significant number of white blood cells which triggered stem cell-based regeneration of new immune system cells, thus stimulating strengthened immune function.
Later, they found in both animal and human studies that a modified fast of suppressing calories to 800 or fewer, for a few days at a time, achieved very similar health benefits to water-only fasting.
Clears the body of toxins, mucous, yeast, and bacteria.
Unfortunately, we currently live in a toxic soup. There are 85,000 chemicals in use in the United States with nearly 5,000 going into our food, air, and water supplies. The average baby is born with about 280 chemicals in their umbilical cord, 180 of which are known carcinogens.7,8
In order to really thrive, you need to clear these toxins, chemicals and carcinogens from your body.
It is the responsibility of your liver, kidneys, lungs, colon, lymphatic system, and skin to eliminate these pathogens and waste products. In order to support them in their efforts, consider including a diet that mimics a fast through detoxification principles. This process eliminates those deeply embedded toxins through your natural detoxification pathways.
An example of this is bisphenol-A (BPA), a synthetic estrogen that leaches out of plastics and other material and hides in your fat cells. In fact, this toxic chemical is so prevalent it is difficult to avoid, does not degrade or break down, ever, and has been linked to cancer, cardiovascular disease, and diabetes.
This is just one of many toxins we are faced with. The good news? Fasting can help optimize detoxification processes and pathways, and give the body time and space to eliminate at a much higher rate.
Improves immune function against cancer cells.
Dr. Longo and Sebastian Brandhorst, another researcher from the Longevity Institute at USC, believe that periodic fasting demonstrates a wide range of beneficial effects that help prevent cancer and increase the effectiveness of current cancer therapies.9
One of their many studies at USC revealed that a diet that a modified fast could trigger the same effects produced by immunotherapy—a therapy that relies on the immune system to kill cancer cells.
The study found that the modified fast weakened the cancer cells and revved up the immune system—making chemo more effective against the cancer and less toxic to healthy cells.2
Improves markers associated with diabetes.
There are several studies that suggest periods of fasting improve insulin sensitivity, which decreases the risk of developing diabetes.
A study published in 2017 revealed that a four-day modified fasting diet triggered changes in mice that led to pancreatic β cell regeneration and the return of insulin secretion—changes that correspond to the reversal of type 2 diabetes.10
Another study showed the regeneration of insulin-producing beta cells as well as the reversal of both type 1 and type 2 diabetes symptoms.
Improves markers associated with neurological health, including multiple sclerosis.
While still under clinical and laboratory investigation, Dr. Longo and his team of researchers have had remarkable results with mice placed on the modified fast he calls the “fasting-mimicking diet.” One study showed the reduction or elimination of the symptoms of multiple sclerosis as well as regeneration of the damaged myelin sheath in their spinal cords.
In older mice, this type of fast promoted new nerve growth in the hippocampus (the part of the brain involved in the formation of new memories) as well as improving cognitive performance and decreasing the risk factors associated with diabetes, cardiovascular disease, and cancer.11
Reduces markers associated with heart disease.
When researchers asked 71 participants to complete three cycles of a modified fasting diet, the results were remarkable.
In addition to weight loss, subjects reduced their blood pressure, total cholesterol, and C-reactive protein (CRP), a marker of inflammation.12
Increases life expectancy.
An article in Mechanisms of Aging and Development reported that it has been well-known for some 70 years, and backed by studies, that restricting the food intake of rats, mice, hamsters, dogs, fish, and even yeast extends their life span.12 When mice eat 30 to 40 percent fewer calories, they developed half the tumors and other diseases than their cousins eating a normal diet.
Our bodies renew themselves on a daily basis. In fact, it is estimated that in one year’s time, 98 percent of our body is replaced. We have a new liver in about 6 weeks, new skin every 30 days, and our gastrointestinal tract regenerates in less than a week. This suggests how powerful our opportunity for a fresh new start is!
Giving your digestive system a break by minimizing your food intake and making sure that what you do eat is pure, natural, and easy to digest gives the 60 trillion cells that make up your body a chance to come clean and be the brilliant purpose-filled organisms that they are.
And the easiest foods to digest are raw, simple plant foods.
You Don’t Have To Starve On A Fasting Diet
You don’t have to limit yourself to water for weeks at a time in order to obtain the health benefits associated with fasting. Undergoing a unique plant-based detoxification program can result in the same biological rewards without the feelings associated with starvation.
Detoxification “Fasting Diet”
The 26-day detox that I undertake twice a year has four phases, which systematically cleanses the colon, liver, kidneys, gallbladder, lymphatic system, and blood.
The first phase prepares your body for fasting by limiting your daily intake to meals that consist of vegetables and a bit of oatmeal for the first four days.
This is followed by a “fast” of green smoothies for three days—giving your body the nutrients it needs while it enters the biological fasting phase.
This green smoothie fast in the first week is followed by a schedule of re-introducing categories of foods (so this detoxification protocol also qualifies as an “elimination diet”), giving specific organs a chance to rest.
After a period of breaking down and eliminating catarrhal mucoid plaque from the 35 feet of the gastrointestinal tract, and after a kidney cleanse, you are ready for a liver and gallbladder flush.
You can watch a free video masterclass about the science and purpose behind this kind of highly cleansing diet to achieve many of the benefits of fasting without actually depriving yourself of food completely.
The “Healing Crisis” That Isn’t
I was surprised after my first major detox, when I was in my early 30’s, that my body released emotions as well as toxins. Emotions that had long been buried came to the surface and passed through me—leaving me forever. I talk more about the experience of this “emotional detox” in the last video of the masterclass.
In addition to uncomfortable emotions, a deep cleanse can also result in what is known as a healing crisis, or “Herxheimer reactions.” These include headaches, skin rashes, lower energy, itching, and diarrhea, to name the most common, for a day or two, and occasionally longer.
In actuality, it is not a crisis but a sign of toxicity leaving the body—your body is cleaning out the toxins, bacteria, viruses, and chemicals that have lodged in your tissues.
Unfortunately, these toxins must pass through the bloodstream in order to be flushed out of your body. As they are filtered and eliminated from your body, you can experience cleansing symptoms that include:
- Muscle or joint aches and pains
- Low-grade fever
- Symptoms associated with a previous illness or injury
- Anxiety and mood swings
- Skin breakouts
- Loss of energy
Consider these passing symptoms as a sign that your body is cleaning out its cells and tissues which will leave you, ultimately, in a state of regeneration and renewal. (For more significant reactions, see your functional medicine practitioner and discontinue or modify the cleanse protocol.)
There are ways to clear these cleansing reactions more quickly:
- drink lots of water
- get plenty of rest
- dry-brush your skin (to improve lymphatic flow) and massage your colon to help in the elimination process
- spend time in an infrared sauna
- get a professional massage
- try a coffee enema.
And know that this, too, shall pass; cleansing crises rarely last longer than a day or two. (Again, if your reactions are severe, consult your trusted healthcare practitioner immediately.)
Side Effects of Fasting
While Herxheimer reactions can be considered “side effects” of fasting, they signal that healing is taking place. But there are other fasting side effects to be aware of–ones that tell you it may be time to stop your fast and begin re-introducing your body to whole, healthy foods.
Ever see Dallas Buyers Club, a movie that starred Matthew McConaughey as an AIDS patient? In order to look the part of a man dying from AIDS, he decided to go on a stringent diet. In four months, he lost 47 pounds and definitely got the look he was going for–hollowed-out cheeks and a body that looked like it could not support his head.
Besides the gaunt look, extreme and prolonged fasting/dieting can lead to muscle weakness and a compromised immune system. At a certain stage, the detrimental side effects of this type of fasting diet outweigh any benefits. These side effects include:
- Irregular heartbeat
- Muscle weakness
- Disorientation or confusion
- Susceptibility to illness (possible sign of weakened immune function)
- Abdominal swelling with pain in the upper right abdomen (possible signs of liver damage)
- Fluid retention and decreased urine output (signaling possible kidney damage)
Choose A Fasting Diet Wisely
Many individuals report relief from chronic diseases after undergoing a fasting diet. But it’s important to choose one that doesn’t end up causing other problems.
A saying from the Ayurveda healing system describes it perfectly: “When lifestyle is wrong, medicine is of no use. When lifestyle is right, medicine is of no need.”
In my experience, the 26-day detox is a fasting-like diet that enables the body to cleanse and rebuild, like fasting does, but anyone can do the 26-day detox. (Most people have never fasted for even a day and are fearful of the process. If that’s you, try a dedicated detox first!)
This protocol provides a safe avenue for ridding the body of toxins, while giving your cells the nutrition they need to regenerate healthy tissues and systems.
Who Should Not Fast?
If you are pregnant or suffer from an eating disorder, now is not the time to undergo a fast. If you have a serious illness, discuss the protocol with your health care provider before considering a fasting diet of any kind.
Conclusion: Fasting Diets
- Fasting has been used for cleansing, renewal, and spiritual awakening for thousands of years.
- There are several different types of fasting diet regimens including water and juice fasting, dry fasting, the Fasting-Mimicking Diet (FMD), intermittent fasting, alternate-day fasting, and time-restrictive eating.
- Water and juice fasting, as well as FMD (fasting mimicking), get your body into a biological fasting state and offer the most dramatic changes in terms of cleansing and rejuvenation.
- Fasting has been shown in studies to increase longevity; reduce blood pressure, cholesterol, triglycerides, inflammation, and C-reactive protein; clear the body of toxins, mucous, yeast, bacteria, and cancer cells; promote cellular renewal and stem cell-based regeneration; increase mental clarity and energy, and may help play a role in reversing significant illness like multiple sclerosis, cancer, and diabetes.
Robyn Openshaw, MSW, is the bestselling author of The Green Smoothies Diet, 12 Steps to Whole Foods, and 2017’s #1 Amazon Bestseller and USA Today Bestseller, Vibe. Learn more about how to make the journey painless, from the nutrient-scarce Standard American Diet, to a whole-foods diet, in her free video masterclass 12 Steps to Whole Foods.
- Olsen, Brad. Modern Esoteric: Beyond Our Senses. CCC Publishing. 08/2017.
- Fung, Jason Dr. How to Fix Your Broken Metabolism by Doing the Exact Opposite. Intensive Dietary Management. https://idmprogram.com/fix-broken-metabolism/
- Longo, Valter PhD. The Longevity Diet. Avery. 2018.
- Trepanowski, John F. et al. Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults. Jama Internal Medicine. 07/2017. https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2623528
- Fond, Guillaume et al. Fasting in Mood Disorders: Neurobiology and Effectiveness. A Review of the Literature. Psychiatry Research. 10/2013. https://www.sciencedirect.com/science/article/pii/S0165178112008153
- Wu, Suzanne. Fasting Triggers Stem Cell Regeneration of Damaged, Old Immune System. USC News. 06/2014. https://news.usc.edu/63669/fasting-triggers-stem-cell-regeneration-of-damaged-old-immune-system/
- Openshaw, Robyn. 26-Day Detox. Robyn Openshaw/GreenSmoothieGirl.com. 12/2017.
- Fitzgerald, Randall. The Hundred-Year Lie: How to Protect Yourself from the Chemicals That Are Destroying Your Health. Dutton. 2006.
- Brandhorst S, Longo VD, Fasting and Caloric Restriction in Cancer Prevention and Treatment. Recent Results in Cancer Research. 10/2016. https://www.ncbi.nlm.nih.gov/pubmed/27557543
- Cheng, Chia-Wei et al. Fasting-Mimicking Diet Promotes Ngn3-Driven β-Cell Regeneration to Reverse Diabetes. Cell. 02/2017. https://www.cell.com/cell/fulltext/S0092-8674(17)30130-7
- Brandhorst, S. et al. A Periodic Diet that Mimics Fasting Promotes Multi-System Regeneration, Enhanced Cognitive Performance, and Healthspan. Cell Metabolism. 07/2015. https://www.ncbi.nlm.nih.gov/pubmed/26094889
- Wei, Min et al. Fasting-mimicking Diet and Markers/Risk Factors for Aging, Diabetes, Cancer, and Cardiovascular Disease. Science Translational Medicine. 02/2017. http://stm.sciencemag.org/content/9/377/eaai8700
- Masoro, EJ. Overview of Caloric Restriction and Ageing. Mechanism of Aging and Development. 09/2005. https://www.ncbi.nlm.nih.gov/pubmed/15885745/
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