First of all, fast is not starvation. Starvation is the involuntary absence from eating forced upon by outside forces; this happens in times of war and famine when food is scarce. Fasting, on the other hand, is voluntary, deliberate, and controlled. Food is readily available but we choose not to eat it due to spiritual, health, or other reasons.

Fasting is as old as mankind, far older than any other forms of diets. Ancient civilizations, like the Greeks, recognized that there was something intrinsically beneficial to periodic fasting. They were often called times of healing, cleansing, purification, or detoxification. Virtually every culture and religion on earth practice some rituals of fasting.

Before the advent of agriculture, humans never ate three meals a day plus snacking in between. We ate only when we found food which could be hours or days apart. Here, from an evolution standpoint, eating three meals a day is not a requirement for survival. Otherwise, we would not have survived as a species.

Fast forward to the 21st century, we have all forgotten about this ancient practice. After all, fast is really bad for business! Food manufacturers encourage us to eat multiple meals and snacks a day. Nutritional authorities warn that skipping a single meal will have dire health consequences. Overtime, these messages have been so well-drilled into our heads.

Fasting has no standard duration. It may be done for a few hours to many days to months on end. Intermittent fast is an eating pattern where we cycle between fasting and regular eating. Shorter fasts of 16-20 hours are generally done more frequently, even daily. Longer fasts, typically 24-36 hours, are done 2-3 times per week. As it happens, we all fast daily for a period of 12 hours or so between dinner and breakfast.

Fasting has been done by millions and millions of people for thousands of years. Is it unhealthy? No. In fact, numerous studies have shown that it has unhealthy health benefits.

What Happens When We Eat Constantly?

Before going into the benefits of intermittent fasting, it is best to understand why eating 5-6 meals a day or every few hours (the exact opposite of fasting) may actually do more harm than good.

When we eat, we ingest food energy. The key hormone involved is insulin (produced by the pancreas), which increases during meals. Both carbohydrates and protein stimulate insulin. Fat triggers a smaller insulin effect, but fat is rarely eaten alone.

Insulin has two major functions –

  • First, it allows the body to immediately start using food energy. Carbohydrates are rapidly converted into glucose, raising blood sugar levels. Insulin directs glucose into the body cells to be used as energy. Proteins are broken down into amino acids and excess amino acids may be turned into glucose. Protein does not unnecessarily raise blood glucose but it can stimulate insulin. Fats have minimal effect on insulin.
  • Second, insulin stores away excess energy for future use. Insulin converters excess glucose into glycogen and store it in the liver. However, there is a limit to how much glycogen can be stored away. Once the limit is reached, the liver starts turning glucose into fat. The fat is then put away in the liver (in excess, it becomes fatty liver) or fat deposits in the body (often stored as visceral or belly fat).

Therefore, when we eat and snack throughout the day, we are constantly in a fed state and insulin levels remain high. In other words, we may be spending the major of the day storing away food energy.

What Happens When We Fast?

The process of using and storing food energy that occurs when we eat goes in reverse when we fast. Insulin levels drop, prompting the body to start burning stored energy. Glycogen, the glucose that is stored in the liver, is first accessed and used. After that, the body starts to break down stored body fat for energy.

Thus, the body basically exists in two states – the fed state with high insulin and the fast state with low insulin. We are either storing food energy or we are burning food energy. If eating and fasting are balanced, then there is no gain gain. If we spend the majority of the day eating and storing energy, there is a good chance that overtime we may end up gaining weight.

Intermittent Fasting Versus Continuous Calorie-Restriction

The portion-control strategy of constant caloric reduction is the most common dietary recommendation for weight loss and type 2 diabetes. For example, the American Diabetes Association recommends a 500-750 kcal / day energy deficit coupled with regular physical activity. Dietitians follow this approach and recommend eating 4-6 small meals throughout the day.

Does the portion-control strategy work in the long-run? Rarely. A cohort study with a 9-year follow-up from the United Kingdom on 176,495 obese individuals indicated that only 3,528 of them succeeded in attaining normal body weight by the end of the study. That is a failure rate of 98%!

Intermittent fast is not constant caloric restriction. Restricting calories causes a compensatory increase in hunger and worse, a decrease in the body's metabolic rate, a double curse! Because when we are burning fewer calories per day, it becomes increasingly harder to lose weight and much easier to gain weight back after we have lost it. This type of diet puts the body into a “starvation mode” as metabolism revs down to conserve energy.

Intermittent fast does not have any of these drawbacks.

Health Benefits Of Intermittent Fasting

Increases metabolism leading to weight and body fat loss

Unlike a daily caloric reduction diet, intermittent fasting increases metabolism. This makes sense from a survival point. If we do not eat, the body uses stored energy as fuel so that we can stay alive to find another meal. Hormones allow the body to switch energy sources from food to body fat.

Studies demonstrate this phenomenon clearly. For example, four days of continuous fast increased Basal Metabolic Rate by 12%. Levels of the neurotransmitter norepinephrine, which prepares the body for action, increased by 117%. Fatty acids in the bloodstream increased over 370% as the body switched from burning food to burning stored fats.

No loss in muscle mass

Unlike a constant calorie-restriction diet, intermittent fasting does not burn muscles as many have feared. In 2010, researchers looked at a group of subjects who underwent 70 days of alternate daily fasting (ate one day and fasted the next). Their muscle mass started off at 52.0 kg and ended at 51.9 kg. In other words, there was no loss of muscles but they did lose 11.4% of fat and saw major improvements in LDL cholesterol and triglyceride levels.

During fasting, the body naturally produces more human growth hormone to preserve lean muscles and bones. Muscle mass is generally preserved until body fat drops below 4%. Therefore, most people are not at risk of muscle-wasting when doing intermittent fasting.

Reverses insulin resistance, type 2 diabetes, and fatty liver

Type 2 diabetes is a condition where there is simply too much sugar in the body , to the point that the cells can no longer respond to insulin and take in any more glucose from the blood (insulin resistance), resulting in high blood sugar. Also, the liver becomes loaded with fat as it tries to clear out the excess glucose by converting it to and storing it as fat.

Therefore, to reverse this condition, two things have to happen –

  • First, stop putting more sugar into the body.
  • Second, burn the remaining sugar off.

The best diet to achieve this is a low-carbohydrate, moderate-protein, and high-healthy fat diet, also called ketogentic diet. (Remember that carbohydrates increases blood sugar the most, protein to some degree, and fat the least.) That is why a low-carb diet will help reduce the burden of incoming glucose. For some people, this is already sufficient to reverse insulin resistance and type 2 diabetes. However, in more severe cases, diet alone is not sufficient.

What about exercise? Exercise will help burn off glucose in the skeletal muscles but not all the tissues and organs, including the fatty liver. Clearly, exercise is important, but to eliminate the excess glucose in the organs, there is the need to temporarily “starve” the cells.

Intermittent fast can accomplish this. That is why historically, people called fast a cleanse or a detox. It can be a very powerful tool to get rid of all the excesses. It is the fastest way to lower blood glucose and insulin levels, and ultimately reversing insulin resistance, type 2 diabetes, and fatty liver.

By the way, taking insulin for type 2 diabetes does not address the root cause of the problem, which is excess sugar in the body. It is true that insulin will drive the glucose away from the blood, resulting in lower blood glucose, but where does the sugar go? The liver is just going to turn it all into fat, fat in the liver and fat in the abdomen. Patients who go on insulin often end up gaining more weight, which worsens their diabetes.

Enhances heart health

Overtime, high blood glucose from type 2 diabetes can damage the blood vessels and nerves that control the heart. The longer one has diabetes, the higher the chances that heart disease will develop. By lowering blood sugar through intermittent fasting, the risk of cardiovascular disease and stroke is also reduced.

In addition, intermittent fasting has been shown to improve blood pressure, total and LDL (bad) cholesterol, blood triglycerides, and inflammatory markers associated with many chronic diseases.

Boosts brain power

Multiple studies demonstrated fasting has many neurologic benefits including attention and focus, reaction time, immediate memory, cognition, and generation of new brain cells. Mice studies also showed that intermittent fast reduces brain inflammation and delays the symptoms of Alzheimer's.

What To Expect With Intermittent Fasting

Hunger Goes Down

We normally feel hunger pangs about four hours after a meal. So if we fast for 24 hours, does it mean that our hunger sensations will be six times more severe? Of course not.

Many people are concerned that fast will will result in extreme hunger and overeating. Studies shown that on the day after a one-day fast, there is, indeed, a 20% increase in caloric intake. However, with repeated fasting, hunger and appetite surprisingly decrease.

Hunger comes in waves. If we do nothing, the hunger dissipates after a while. Drinking tea (all kinds) or coffee (with or without caffeine) is often enough to fight it off. However, it is best to drink it black though a teaspoon or two of cream or half-and-half will not trigger much insulin response. Do not use any types of sugar or artificial sweeteners. If necessary, bone broth can also be taken during fasting.

Blood sugar does not crash

Sometimes people worry that blood sugar will fall very low during fasting and they will become shaky and sweaty. This does not actually happen as blood sugar is tightly monitored by the body and there are multiple mechanisms to keep it in the proper range. During fasting, the body begins to break down glycogen in the liver to release glucose. This happens every night during our sleep.

If we fast for longer than 24-36 hours, glycogen stores become depleted and the liver will manufacture new glucose using glycerol which is a by-product of the breakdown of fat (a process called gluconeogenesis). Apart from using glucose, our brain cells can also use ketones for energy. Ketones are produced when fat is metabolized and they can supply up to 75% of the brain's energy requirements (the other 25% from glucose).

The only exception is for those who are taking diabetic medications and insulin. You MUST first consult your doctor as the dosages will probably need to be reduced while you are fasting. Otherwise, if you overmedicate and hypoglycemia develops, which can be dangerous, you must have some sugar to reverse it. This will break the fast and make it counter productive.

The dawn phenomenon

After a period of fasting, especially in the morning, some people experience high blood glucose. This dawn phenomenon is a result of the circadian rhythm wherebyby just before awakening, the body secretes higher levels of several hormones to prepare for thecoming day –

  • Adrenaline – to give the body some energy
  • Growth hormone – to help repair and make new protein
  • Glucagon – to move glucose from storage in the liver to the blood for use as energy
  • Cortisol, the stress hormone – to activate the body

These hormones peak in the morning hours, then fall to lower levels during the day. In non-diabetics, the magnitude of the blood sugar rise is small and most people will not even notice it. However, for the majority of the diabetics, there can be a noticeable spike in blood glucose as the liver dumps sugar into the blood.

This will happen in extended fasts too. When there is no food, insulin levels stay low while the liver releases some of its stored sugar and fat. This is natural and not a bad thing at all. The magnitude of the spike will decrease as the liver becomes less bloated with sugar and fat.

Who Should Not Do Intermittent Fasting?

  • Women who want to get pregnant, are pregnant, or are breastfeeding.
  • Those who are malnourished or underweight.
  • Children under 18 years of age and elders.
  • Those who have gout.
  • Those who have gastroesophageal reflux disease (GERD).
  • Those who have eating disorders should first consult with their doctors.
  • Those who are taking diabetic medications and insulin must first consult with their doctors as dosages will need to be reduced.
  • Those who are taking medications should first consult with their doctors as the timing of medications may be affected.
  • Those who feel very stressed or have cortisol issues should not fast because fasting is another stressor.
  • Those who are training very hard most days of the week should not fast.

How To Prepare For Intermittent Fasting?

If anyone is thinking about starting intermittent fasting, it is best to first switch to a low-carbohydrate, high-healthy fat diet for three weeks. This will allow the body to become accustomed to using fat rather than glucose as a source of energy. That means getting rid of all sugars, grains (bread, cookies, pastries, pasta, rice), legumes, and refined vegetable oils. This will minimize most side effects associated with fasting.

Start with a shorter fast of 16 hours, for example, from dinner (8 pm) until lunch (12 pm) the next day. You can eat normally between 12 pm and 8 pm, and you can eat either two or three meals. Once you feel comfortable with it, you can extend the fast to 18, 20 hours.

For shorter fasts, you can do it everyday, continuously. For more extended fasts, such as 24-36 hours, you can do it 1-3 times a week, alternating between fasting and normal eating days.

There is no single fast regimen that is correct. The key is to choose one that works best for you. Some people achieve results with shorter fasts, others may need longer fasts. Some people do a classic water-only fast, others do a tea and coffee fast, still others a bone broth fast. No matter what you do, it is very important to stay hydrated and monitor yourself. If you feel ill at any point, you should stop immediately. You can be hungry, but you should not feel sick.