Intermittent fasting is the practice of occasionally going for extended periods without eating. We all do some form of intermittent fasting every single day, except we don’t call it that. We call it sleeping.
Fasting is one of the most ancient and widespread healing traditions in the world. Humans have fasted for most of their history, whether it’s during the typical overnight period, during more extended periods of food scarcity, or for religious reasons.
Hippocrates (460 – 370 BC) prescribed the practice of fasting. He wrote, “To eat when you are sick, is to feed your illness”. The ancient Greek writer and historian Plutarch (46 – 120 AD) also echoed these sentiments. He wrote, “Instead of using medicine, better fast today . ” Ancient Greek thinkers Plato and his student Aristotle were also staunch supporters of fasting. Humans, like most animals, do not eat when they become sick. For this reason, fasting has been called the ‘physician within’.
Fasting for spiritual purposes is widely practiced, and remains part of virtually every major religion in the world. Jesus Christ, Buddha and Prophet Muhammad (صلى الله عليه وسلم )all shared a common belief in the healing power of fasting. In spiritual terms, it is often called cleansing or purification, but practically, it amounts to the same thing. The practice of fasting developed independently among different religions and cultures, not as something that was harmful, but something that was deeply, intrinsically beneficial to the human body and spirit.
In Buddhism, food is often consumed only in the morning, and followers fast from noon until the next morning daily. In addition to this, there may be various water-only fasts for days or weeks on end. Greek Orthodox Christians may follow various fasts over 180-200 days of the year. Muslims fast from sunrise to sunset during the Islamic month of Ramadan. The Prophet Muhammad (صلى الله عليه وسلم ) also encouraged fasting on Mondays and Thursdays of every week. Ramadan is the best studied of the fasting periods. It differs from many fasting protocols in that fluids are also forbidden. In addition to fasting, they also undergo a period of mild dehydration.
Physiological Changes to the Body during Fasting
The transition from the fed state to the fasted state occurs in several stages:
1. Feeding– During meals, insulin levels are raised. This allows uptake of glucose into tissues such as the muscle or brain to be used directly for energy. Excess glucose is stored as glycogen in the liver.
2. The Post-Absorptive Phase– 6-24 hours after beginning fasting- Insulin levels start to fall. Breakdown of glycogen releases glucose for energy. Glycogen stores last for roughly 24 hours.
3. Gluconeogenesis– 24 hours to 2 days after fasting– The liver manufactures new glucose from amino acids in a process called “gluconeogenesis”. Literally, this is translated as “making new glucose”. In non-diabetic persons, glucose levels fall but stay within the normal range.
4. Ketosis– 2-3 days after beginning fasting– The low levels of insulin reached during fasting stimulate lipolysis, the breakdown of fat for energy. The storage form of fat, known as triglycerides, is broken into glycerol and fatty acids. Glycerol is used for gluconeogenesis. Fatty acids may be used directly for energy by many tissues in the body, but not the brain. Ketone bodies, capable of crossing the blood-brain barrier, are produced from fatty acids for use by the brain. After four days of fasting, approximately 75% of the energy used by the brain is provided by ketones.
5. Protein Conservation Phase– 5 days after fasting– High levels of growth hormone maintain muscle mass and lean tissues. The energy for maintenance of basal metabolism is almost entirely met by the use of free fatty acids and ketones. Increased adrenalin levels prevent the decrease in metabolic rate.
The human body has well developed mechanisms for dealing with periods of low food availability. In essence, what we are describing here is the process of switching from burning glucose (short term) to burning fat (long term). Fat is simply the body’s stored food energy. In times of low food availability, stored food is naturally released to fill the void. The body does not ‘burn muscle’ in an effort to feed itself until all the fat stores are used.
Intermittent Fasting Benefits
Below are only some of the amazing benefits of intermittent fasting:
Helps You Lose Weight and Belly Fat
· Improves appetite control - Intermittent fasting will generally make you eat fewer meals and eat less calories.
· Intermittent fasting enhances hormone function to facilitate weight loss.
· Lower insulin levels, higher growth hormone levels and increased amounts of noradrenaline all increase the breakdown of body fat and facilitate its use for energy.
· Increased growth hormone release - helps to preserve muscle mass and bone density as well as aid fast recovery after exercise.
· Increases Metabolic Rate – after only 48 hours of fasting a 3.6% increase in metabolic rate was seen which was stimulated by the release of adrenalin. The increase in adrenalin boosts energy even while in resting state.
· Fasting transitions the body from burning sugar to burning fat and increases in fat burning.
Lowers Insulin Resistance - Prevent Type 2 Diabetes
· Improves blood sugar control - by lowering blood glucose and increasing insulin sensitivity.
· Blood levels of insulin drop significantly, which facilitates fat burning. This effect is seen with fasting periods as short as 24-36 hours.
· Longer duration fasts reduce insulin even more dramatically.
· Regular fasting, in addition to lowering insulin levels, has also been shown to improve insulin sensitivity significantly.
Beneficial For Heart Health
· Intermittent fasting has been shown to improve numerous different risk factors, including blood pressure, total and LDL cholesterol, blood triglycerides, inflammatory markers and blood sugar levels.
· Improves cardiovascular function by offering protection against ischemic injury to the heart.
· It lowers blood lipids including decreasing triglycerides and LDL cholesterol.
· It lowers blood pressure through changes in sympathetic/parasympathetic activity
Reduces Oxidative Stress and Inflammation in the Body
· A study from Obesityshows that fasting produces an anti-inflammatory effect on the neuroimmune system that a high-fat diet would otherwise prevent.
· Lowers markers of inflammation (including CRP<, IL-6, TNF, BDNF, and more)
· Intermittent fasting may enhance the body's resistance to oxidative stress.
Good for Your Brain
· Several studies in rats have shown that intermittent fasting may increase the growth of new nerve cells, which should have benefits for brain function.
· It also increases levels of a brain hormone called brain-derived neurotrophic factor (BDNF), a deficiency of which has been implicated in depression and various other brain problems.
· It can also improve neuronal plasticity by offering protection against neurotoxins.
· Animal studies have also shown that intermittent fasting protects against brain damage due to strokes.
· Intermittent fasting may delay the onset of Alzheimer's disease or reduce its severity.
· Fasting may protect against other neurodegenerative diseases, including Parkinson's and Huntington's disease but more studies are needed to confirm this.
Repairs Damaged Cells
· When we fast, the cells in the body initiate a cellular "waste removal" process called autophagy.
· This involves the cells breaking down and metabolising broken and dysfunctional proteins that build up inside cells over time.
· Autophagy helps cells overcome stresses brought on from external causes like the deprivation of important nutrients, as well as internal issues like pathogens or invading infections organisms.
· Increased autophagy may provide protection against several diseases, including cancer and Alzheimer's disease.
Helps You Live Longer
· There are beneficial changes in several genes and molecules related to longevity and protection against disease.
· Studies in rats have shown that intermittent fasting extends lifespan in a similar way as continuous calorie restriction.
· In some of these studies, the effects were quite dramatic. In one of them, rats that fasted every other day lived 83% longer than rats who didn’t fast.
Fasting for Health
Fasting is defined as the voluntary act of withholding food for a specific period of time. In some fasting schedules non-caloric drinks such as water and tea are permitted. An absolute fast refers to the withholding of both food and drink. This may be done for religious purposes, such as during Ramadan in Islam.
Here are some popular methods used today for improving health:
· The 16/8 Method- It involves skipping breakfast and restricting your daily eating period to 8 hours, for example from 1 pm to 9 pm. Then you "fast" for 16 hours in between.
· Eat-Stop-Eat- This involves fasting for 24 hours, once or twice a week, for example by not eating from dinner one day until dinner the next day.
· The 5:2 Diet- On two non-consecutive days of the week, only eat 500-600 calories. Eat normally the other 5 days.
· The ‘Warrior’ diet– The core of the diet consists of eating all meals in the evening during a 4 hour window. The fasting period of 20 hours consisted of most of the day. There was also an emphasis on natural unprocessed foods and high intensity training.
· Alternate-day fasting- Fasting every other day, either by not eating anything or only eating a few hundred calories.
If you are an all-around healthy person, there is no risk in trying intermittent fasting. But anyone with an eating disorder, a history of eating disorders, or body dysmorphia should not try intermittent fasting. People with diabetes, women who are pregnant or breastfeeding, and those taking prescription medication that has to be taken at a specific time with food are also not candidates for intermittent fasting.
Careful monitoring by a health professional should be done if you are planning to fast longer than 24 hours. If you feel unwell at any point during the fasting, you must stop. You may feel hungry, but you should not feel faint, or unwell or nauseated. This is not normal and you should not attempt to ‘push through’. Be wary of a condition known as hypoglycaemia which often manifests as shaking, sweating and sometimes seizures.
The natural rhythm of life is Feast and Fast. There are times that you should feast (weddings, celebrations), and there are times that you should fast. Intermittent. To go on a ‘diet’ or restrict calories for years could be harmful and ultimately may prevent you from shifting the excess fat. Always consult your physician for advice.
To Sum Up…
Fasting is truly an idea that has withstood the test of time. It has been used for weight loss, to improve heart health, extend life, prevent Alzheimer’s, prevent insulin resistance and even slow down the entire aging process. Rather than something we’re forced to endure – a result of poor food availability or cultural expectations – intermittent fasting is becoming something that health and physique-oriented people are seeking out in order to keep their bodies in top shape. What’s new is that clinical research on intermittent fasting benefits for health and longevity is now beginning to catch up.