The Truth About Fasting: Although fasting has hit the mainstream, it is not a fad diet. With ancestral roots in religion, fasting is not limited to spirituality either. Today we dive into all things fasting and why it may be a habit to implement into your lifestyle.
The Truth About Fasting: What is Fasting?
Fasting is simply the period between eating. Technically you fast between every meal and, more notably, between your last meal and your breakfast. There are various kinds of fasts, including mono-fasts (consuming only one type of food), juice fasts (drinking only juice), water fasts (consuming only water), and dry fasts (consuming nothing at all).
Fasting can also refer to the period that you go without food or only drinking water. You may also be allowed to consume tea, electrolytes, salt, fatty coffee, or even small amounts of food during the “fasting period.”
Types of Fasting
As we have noted, there are many kinds of fasting. But some of the four most common and studied types include intermittent, alternate-day, prolonged, or a fasting-mimicking diets.
Time-Restricted Feeding (Intermittent Fasting)
Time-restricted feeding, also known as intermittent fasting, condenses all your eating into an eating window of under 12 hours. So if you have dinner at 8 p.m., you won’t have breakfast until 8 a.m; at the earliest. As you become more metabolically flexible, the eating window can be shortened, ideally to around six hours. Some people go as tight as one meal (known as one meal a day fasting, or OMAD).
The simplest way to start intermittent fasting is to skip either dinner or breakfast.
Alternate-day fasting is simply fasting for a total of 24 hours every other day. Typically this kind of fasting is paired with “feast” days on the non-fasting days. Although it is a less sustainable protocol than many others, it is often pursued as a method for rapid weight loss.
Prolonged Water Fasting
Longer fasts range in length, but a minimum of three days is suggested to start reaping the benefits.1 These fasts are typically done by consuming only water and occasionally electrolytes or salt. They can be implemented more often, for example, monthly or as a seasonal reset.
Although the benefits kick in after three days, five days is a better goal to reap more of the benefits of your fast. Longer water fasts can be done but should be supervised.
The fasting-mimicking diet is perhaps the most sustainable of all the fasting methods since it still allows you to consume food. The fasting-mimicking diet will enable you to eat around 20% to 25% of your typical daily energy needs on scheduled fast days, which typically go for five days straight. This caloric intake is a mindful balance of macronutrients to support ketosis so that despite eating food, you are still achieving autophagy and other benefits of fasting without any food.2
Fasting Around The World and Through the Ages
Fasting is found in nearly every major religious tradition worldwide, including Buddhism, Christianity, Hinduism, Islam, and Judaism.3
Going a time without food for therapeutic purposes also has very ancestral roots, dating back to ancient Greece, when Hippocrates (the “father of modern medicine”) advocated for it as a way for the body to heal itself.4 Despite its ancient roots, fasting has occurred throughout the ages thanks to many religious practices. In Ramadan, for example, Muslims are to fast from dawn to sunset every day for a month.5
In recent times, fasting has made a resurgence in popularity thanks to science. With ever-growing evidence supporting the benefits of fasting for health, weight loss, muscle tone, and longevity– fasting is becoming popular for anyone looking to improve their well-being.
The Truth About Fasting: Why People Fast
Apart from religious practices, one of the most significant reasons people fast is for weight loss. However, no matter the reason for fasting, the other side effects are profoundly beneficial. For example, studies show that fasting may help improve your glucose levels, insulin sensitivity, cholesterol, blood pressure, and other health issues.6-8
Fasting and Hunger
One of the most common questions about fasting is, “will I be hungry”? And the answer is: it depends. Your mindset, health state, and metabolic flexibility going into a fast will be the most significant determining factors to your hunger levels during a fast.
For those that are more metabolically flexible and overall healthy, many people report no sensations of hunger at all. However, signs of hunger later in a fast (sometimes not until day 10) are usually signs that it’s time to break the fast.
For others, hunger does come and generally passes relatively quickly. One of the biggest triggers for hunger is actually routine. Hunger pangs will occur during the time of day when you usually eat a meal. This can be a good time to sip on some salted water and wait for the hunger to pass. Distracting yourself from a task during typical meal times is another way to help reduce the intensity and duration of hunger during a fast.
The Truth About Fasting: Who Can Fasting Benefit?
The benefits of fasting are so far-reaching that nearly anyone will benefit from it. From reversing various ailments to promoting health and longevity, fasting is one of the most universally healing and accessible modalities on the planet.
Some of the top benefits include:
1. Promotes Balance of Blood Sugar and Insulin Sensitivity
Studies on all different kinds of fasting show that fasting may improve blood sugar levels.9 In addition, fasting has been linked with improved insulin sensitivity, meaning that the insulin receptors work more effectively, even once the fast is over. Such studies have also been done on people with diabetes, demonstrating the blood-sugar balancing benefits during a fast and plausible solution for reversing diabetes long-term.6
2. Reduces Inflammation
Chronic inflammation is a marker of essentially all disease models.10As such; we are mitigating the long-term chronic inflammation in the body should be important to anyone who wants a long and healthy life. In addition, fasting has been shown to significantly decrease inflammatory markers in the body in intermittent fasting and a fasting-mimicking diet.
3. Promotes Heart Health
Although heart disease is the single most giant killer in America, studies suggest that altering your lifestyle is the most effective way of reducing your risk. Fasting has been linked to balanced blood pressure, improved triglyceride markers, and improved cholesterol levels– all crucial factors in generating heart health7,13
4. Boosts Cognitive Health and Prevents Neurodegenerative Disorders
Fasting shows promising results in the world of cognitive and neurodegenerative health. For example, one study highlights the ability of intermittent fasting to improve brain function and structure.14 This may be partly due to the highly anti-inflammatory nature of fasting.
Studies also show the profound impact that fasting may have on preventing or even reversing a wide range of neurodegenerative diseases like Alzheimer’s and Parkinson’s.15-16
5. Improves Metabolic Health and Promotes Weight Loss
The specific mechanisms behind why fasting promotes weight loss go far beyond calories-in and calories-out. Caloric intake has very little to do with the long-term weight loss benefits sustained through fasting. More relevant are various aforementioned benefits, including increased insulin sensitivity and reduction of inflammation.9,11
Studies comparing caloric restriction with fasting parameters demonstrate that fasting promotes more fat loss while preserving muscle tissue.17
6. Promotes Longevity
Although the longevity studies are currently limited to animal models, the results are so astounding that you might do a double-take. For example, one study delayed the aging of rats and extended their lifespan by 83% compared to the non-fasted rats.18 Studies on various other animals suggest similar findings, so although no human-longevity studies exist yet, you can bet that between all the benefits mentioned in points one through five, implementing fasting into your lifestyle is likely to increase your time on the planet too.19-20
The Truth About Fasting: Is Fasting Safe?
Many of the benefits surrounding fasting have a homeostasis effect, meaning that they help bring your current state into balance. For example, cholesterol levels will find balance, whether too high or too low. Similarly, the weight will drop in someone overweight, but muscle can be promoted in someone underweight.
If you are currently on medication, fasting should be done supervised by your medical practitioner since the dosage of your medication will have to be altered during a fast.
Fasting is not recommended for women who are pregnant or breastfeeding. It is also not recommended for individuals with disordered eating habits since it can be psychologically destabilizing to restrict food severely.
Fasting should not be taught to or promoted in children and teenagers for psychological reasons, but both age groups do it naturally fast. One way to cultivate a healthy relationship with food and fasting may be to not force meals or mealtimes in children and teens by letting them eat intuitively.
Ease Into Fasting
Prolonged or alternate-day fasting could be tough to stick with over the long term, especially if you are new to fasting. Other versions of fasting, like intermittent fasting or the fasting-mimicking diet, can help ease you into longer fasts by promoting metabolic flexibility and insulin sensitivity.
Although fasting is often linked to a religious habit, the latest science highlights that the benefits extend themselves far beyond spirituality. Various kinds of fasting, including intermittent fasting, prolonged fasting, alternate-day fasting, and the fasting-mimicking diet, all hold similar benefits. These benefits include balancing blood sugar levels, promoting heart health, boosting cognition, improving metabolic health and weight loss, and promoting longevity. Fasting can benefit nearly anyone but should be avoided if you have a history of eating disorders, are pregnant, or are breastfeeding. In addition, longer fasts should be medically supervised.
Medical Disclaimer: This article is based upon the opinions of The Cell Health Team. The information on this website is not intended to replace a one-on-one relationship with a qualified healthcare professional and is not intended as medical advice. It is intended to share knowledge and information from the research. This article has been medically reviewed by Dr. Charles Penick, MD, for the accuracy of the information provided. Still, we encourage you to make your own healthcare decisions based on your research and in partnership with a qualified healthcare professional.
- Cheng, Chia-Wei, et al. “Prolonged Fasting Reduces IGF-1/PKA to Promote Hematopoietic-Stem-Cell-Based Regeneration and Reverse Immunosuppression.” Cell Stem Cell, vol. 14, no. 6, 2014, pp. 810–823., doi:10.1016/j.stem.2014.04.014.
- Wei, Min et al. “Fasting-mimicking diet and markers/risk factors for aging, diabetes, cancer, and cardiovascular disease.” Science translational medicine vol. 9,377 (2017): eaai8700. doi:10.1126/scitranslmed.aai8700
- Kerndt, P R et al. “Fasting: the history, pathophysiology, and complications.” The Western journal of medicine vol. 137,5 (1982): 379-99.
- “Fasting.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., www.britannica.com/topic/fasting.
- “Ramadan.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., www.britannica.com/topic/Ramadan.
- Arnason, Terra G et al. “Effects of intermittent fasting on health markers in those with type 2 diabetes: A pilot study.” World journal of diabetes vol. 8,4 (2017): 154-164. doi:10.4239/wjd.v8.i4.154
- Bhutani, Surabhi et al. “Improvements in coronary heart disease risk indicators by alternate-day fasting involve adipose tissue modulations.” Obesity (Silver Spring, Md.) vol. 18,11 (2010): 2152-9. doi:10.1038/oby.2010.54
- Beleslin, Biljana et al. Srpski arhiv za celokupno lekarstvo vol. 135,7-8 (2007): 440-6. doi:10.2298/sarh0708440b
- Barnosky, Adrienne R et al. “Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings.” Translational research : the journal of laboratory and clinical medicine vol. 164,4 (2014): 302-11. doi:10.1016/j.trsl.2014.05.013
- Hunter, Philip. “The inflammation theory of disease. The growing realization that chronic inflammation is crucial in many diseases opens new avenues for treatment.” EMBO reports vol. 13,11 (2012): 968-70. doi:10.1038/embor.2012.142
- Faris, Mo’ez Al-Islam E et al. “Intermittent fasting during Ramadan attenuates proinflammatory cytokines and immune cells in healthy subjects.” Nutrition research (New York, N.Y.) vol. 32,12 (2012): 947-55. doi:10.1016/j.nutres.2012.06.021
- Choi, In Young et al. “A Diet Mimicking Fasting Promotes Regeneration and Reduces Autoimmunity and Multiple Sclerosis Symptoms.” Cell reports vol. 15,10 (2016): 2136-2146. doi:10.1016/j.celrep.2016.05.009
- Beleslin, Biljana et al. Srpski arhiv za celokupno lekarstvo vol. 135,7-8 (2007): 440-6. doi:10.2298/sarh0708440b
- Li, Liaoliao et al. “Chronic intermittent fasting improves cognitive functions and brain structures in mice.” PloS one vol. 8,6 e66069. 3 Jun. 2013, doi:10.1371/journal.pone.0066069
- Halagappa, Veerendra Kumar Madala et al. “Intermittent fasting and caloric restriction ameliorate age-related behavioral deficits in the triple-transgenic mouse model of Alzheimer’s disease.” Neurobiology of disease vol. 26,1 (2007): 212-20. doi:10.1016/j.nbd.2006.12.019
- Duan, W, and M P Mattson. “Dietary restriction and 2-deoxyglucose administration improve behavioral outcome and reduce degeneration of dopaminergic neurons in models of Parkinson’s disease.” Journal of neuroscience research vol. 57,2 (1999): 195-206. doi:10.1002/(SICI)1097-4547(19990715)57:2<195::AID-JNR5>3.0.CO;2-P
- Varady, K A. “Intermittent versus daily calorie restriction: which diet regimen is more effective for weight loss?.” Obesity reviews : an official journal of the International Association for the Study of Obesity vol. 12,7 (2011): e593-601. doi:10.1111/j.1467-789X.2011.00873.x
- Goodrick, C L et al. “Effects of intermittent feeding upon growth and life span in rats.” Gerontology vol. 28,4 (1982): 233-41. doi:10.1159/000212538
- Honjoh, Sakiko et al. “Signalling through RHEB-1 mediates intermittent fasting-induced longevity in C. elegans.” Nature vol. 457,7230 (2009): 726-30. doi:10.1038/nature07583
- Sogawa, H, and C Kubo. “Influence of short-term repeated fasting on the longevity of female (NZB x NZW)F1 mice.” Mechanisms of ageing and development vol. 115,1-2 (2000): 61-71. doi:10.1016/s0047-6374(00)00109-3