The physiology of fasting is inherent in our species as it is in other animals. It is a survival mechanism for times when food is scarce. A classic example of fasting for survival is hibernation. Animals enter a state of dormancy in which their body temperature, metabolic rate, heart rate, and respiration all drop to conserve energy when food is not available and environmental conditions are unfavourable.
A common physiological feature of most fasting mammals is that their bodies feed on the accumulated fat of their fat stores. We are mammals.
We humans were once hunter gatherers, and experienced conditions when food was scant. To feed a small tribe, hunters would work together to capture a large animal. This might have taken hours, if not days, or even weeks. To adapt, the body stored fat in lean times and burned it in times when food was hard to find.
With the movement of time, tribal members may have noticed changes in themselves during and after fasting, for example increased energy and mental acuity as well as the disappearance of certain illnesses. Longer surviving individuals may have noticed that people lived longer if their food source was not as constant as compared to other tribes, and came to realize that fasting was beneficial.
As tribes increasingly coalesced into larger social groups, spirituality and religion became important. Fasting, since it was known to physically benefit the body, enhance mental acuity and facilitate a spiritual experience, was incorporated into their belief system. Fasting was practised in ancient Egypt, Mesapotamia, and ancient Greece. It is performed in Hinduism, Buddhism, Judaism, Christianity, and Islam.
Today, the need to fast is critical. For many societies, food is constantly available, and there are no feeding and fasting cycles; but our body has not changed. It is still adapted to food scarcity and food abundance cycles. The body cannot cope with a constant consumption of carbohydrates. Hence the prevalence of the growing disorder of modern times: type 2 diabetes.
Intermittent Fasting
Intermittent fasting, or time restricted eating, mimics a food abundant and food scarcity cycle. It is probably the most powerful tool in existence to put T2D into remission given the nature of the disorder. T2D is a dietary disorder caused by too much sugar in the body. The body’s principal energy stores, the liver and body fat are full, and can no longer store any excess.
To recap, normally, when feeding, the liver, heart, and kidneys obtain their energy from glucose drawn from the blood stream. When we are not eating, we still need a source of energy to drive the metabolism of our bodies.
The Energy for Metabolism
To get an idea of the metabolic powerhouse and its needs, it is helpful to know that our energy ultimately comes from ATP (adenosine triphosphate) molecules.
For all cells in the body, glucose is the preferred energy source. Each glucose molecule produces 38 ATP molecules. The body needs 
molecules of ATP per second to survive and at any given moment, it only has enough in store for six seconds of life. Food is digested and carbohydrates are ultimately broken down into the glucose molecules burned to drive the body’s metabolism. The energy required when we are not eating- comes from the body’s stores, the liver and body fat.
The Toggle
The switch from using dietary glucose to non-dietary glucose is signalled by the hormone insulin. When insulin is high the body uses glucose from food, and the excess glucose is stored in the liver as glycogen and is also transformed into fat.
On the other hand, when insulin is low, the glucose comes from body stores.The stored sugar and body fat are burned. This is an ongoing cycle and is the reason why there is always that six-second storage of the necessary amount of ATP to keep us alive when we sleep.
Sugar and The Liver
It follows that by extending the amount of time we sleep or don’t eat, we burn off our body energy stores for a longer period of time. In other words, the longer we are in a fasting state, the more fat we burn off.
During our waking hours, after a typical meal we use the energy from the food we eat, but four hours after finishing that meal, we start to use that stored sugar called glycogen, from the liver.
At that moment the entire body gets its ATP molecules from this source. This liver glycogen store will last for about 24 hours If you habitually consume high amounts of carbohydrates, whereas it will deplete sooner if you eat fewer carbohydrates.
As the liver empties, gluconeogenesis (glucose making) takes place, in which protein, lactates and glycerol are transformed into glucose for energy use. This process occurs after 16 to 28 hours of fasting.
Autophagy
Furthermore, during this time, a process called autophagy is accelerated. The body literally starts to selectively feed on itself; it recycles defective cells and their components.
Damaged cells degrade and their contents are fed into the gluconeogenesis (glucose making) mechanism in the liver. In this way the body provides energy for itself and heals. Studies show that autophagy can unblock atherosclerotic arteries. Cell Metabolism (2011;13 6:655-67).
Acceleration of Metabolism
During fasting, insulin drops, but the counter-regulatory hormones rise:
after 24 hours growth hormone is at about three or four times its normal level and will continue to rise even after five days of fasting. The growth hormone will be necessary to synthesize proteins to rebuild structures when we break the fast;
norepinephrine, and epinephrine (nordrenaline, and adrenaline) are secreted giving an energetic feeling,
metabolic rate is further accelerated by activation of the mechanism responsible for the fight and flight response, the sympathetic nervous system. The heart rate is increased and glucose enters the blood enabling you to fight if you have to, or flee.
Putting Type 2 Diabetes into Remission
Fasting effects a transition from burning glucose derived from food or from the liver to glucose from protein and then body fat. When the glucose levels are high as in the bloodstreams of T2 diabetics, then any extra fasting time will allow us to use up the excess sugar.
If we want to put the disorder into remission and lose weight to below our genetically determined weight threshold, then fasting gives us the time our bodies need to transition from burning glucose directly to burning body fat.
14 Benefits of Intermittent Fasting
1. Autophagy is activated and the body heals.
2. Growth hormone is secreted, which
leads to increased muscle mass, cognitive improvements, weight loss and
healthier arteries.
3. Brain derived neurotrophic factor is
released also giving you better memory, cognition as well as a healthy brain.
4. You get increased energy.
5. Blood pressure normalizes.
6. It lowers insulin resistance.
7. It accelerates weight loss.
8. It reduces low density lipids in the blood thereby reducing the risk of cardiovascular disease.
9. It reverses cardiovascular disease.
10.It reduces inflammation.
11.It raises the levels of healthy high density lipids.
12.It combats aging.
13.It reduces the risk of cancer and can even reverse it.
14.It puts type two diabetes into remission.
10 Fasting Tips for Type 2 Diabetics
1. If you are taking medication to treat type two diabetes, you must first talk to your doctor. Why? Your medication is prescribed according to your diet and you are now going to change the way you eat. By constantly monitoring your blood glucose concentrations, you will avoid steep fluctuations and resulting complications.
For example, sweating and shaking are symptoms of low blood glucose, which is dangerous. You will see that the glucose levels will drop, and your doctor will adjust your medication accordingly
You must always monitor your blood glucose levels. By far the most efficient way to keep track of your blood glucose is with a continuous glucose monitor.
2. Start slowly, have three meals a day with 12 hours of fasting. Remember, included in that 12- hour period is the amount of time you sleep.
3. Cut out snacks, refined sugar, and bread.
4. Lower your carbohydrate intake from 100g down to 50g or 30g per day. It takes time and you might find it difficult.
5. You might find it difficult at first because of hunger. But don’t give up. Hunger is just a sensation. It is brought on by the hormone ghrelin, mostly made in the stomach and partly made in the small intestine. Eur Endocrinol. 2015 Aug; 11(2): 90–95. It adapts to your habitual eating times. For example, if you always eat at 1:00 p.m. a wave of ghrelin occurs before that time, giving you the sensation of hunger. You might say to yourself, “I feel hungry, it must be lunch time.”
After eating, the ghrelin levels drop and we don’t feel hungry. This pattern occurs even if we don’t eat. We will feel hungry, but after the habitual mealtime has passed, ghrelin levels drop, the sensation of hunger subsides, and we will no longer have that craving for food. The takeaway is that if we ignore the hunger sensation at our regular eating times, the feeling of hunger will pass and that ghrelin, which causes the sense of hunger, will adapt to our new eating schedule.
6. Substitute carbohydrates with fat. Eat food that naturally has fat in it: avocados, nuts, beefburgers, whole eggs, fatty fish, cream cheese. Add olive oil, coconut oil or butter to your vegetables.
7. Drink enough water and get minerals from leafy vegetables and supplements like pink salt, and magnesium citrate.
8. Slowly extend your fasting time to about 18 to 20 hours. Reduce to two meals in the eating window. Six weeks after you reach this level, you will see your weight reducing. Remember always communicate with your doctor.
9. Try to fast for 24 hours at least once a week, progressing to three times a week.
10. Try reducing your meals to once a day.
The Benefits of Intermittent Fasting Are Enhanced by Doing Exercise
Exercise how and when you usually do it. You will feel a little tired at first but after a few weeks, your body will adapt
Once you reach the level of being able to fast for 24 hours, exercise optimizes the hormonal benefits: your metabolic rate increases thus burning fat at an even faster rate; you can exercise harder producing more muscle mass which absorbs glucose, and increased growth hormone levels allow you to recover more quickly