What is intermittent fasting and what are the benefits?

January 30, 2020 Evolve Further

Intermittent fasting, refers to a diet that involves avoiding food intake, for a period of time, on a regular basis. Intermittent fasting delivers many benefits beyond just weight-loss, it may even help to extend lifespan. In this article we explore what intermittent fasting is, what benefits it can deliver and various methods of practicing this diet.

What is intermittent fasting?

Intermittent fasting is a special diet in which people have to restrict how much or when they eat food in a given period of time. It involves eating food only during a specific number of hours in a day or week.

Intermittent fasting differs from other diets in that it does not tell you what you can or can’t eat, nor how much to eat. During the feeding times you can eat whatever you want, and as much as you want!

There are various methods of intermittent fasting, some lasting hours and some lasting several days, we will go into more detail on the different methods of fasting later in this article.

Typically, during the period of fasting you may not eat any food, however there are exceptions on some longer fasting programs you may be allowed a small amount of calories. During the fasting period you are allowed to drink water, unsweetened tea and coffee, and other low-calorie beverages.

What are the benefits of intermittent fasting?

Promotes longevity

Animal studies have shown that intermittent fasting can significantly extend lifespan. The results are striking, in one study rats who fasted every other day lived 83% longer on average than the control group (1).

While the effect on longevity hasn’t been proven in humans, intermittent fasting has been shown to deliver a range of benefits in humans which should contribute to increased lifespan, these are outlined below.

Promotes weight loss

Obesity is one of the common precursors to several diseases including heart attacks, high cholesterol, stroke, hypertension, and diabetes. These disorders are known to reduce the lifespan of a person and also affect their quality of life.

Intermittent fasting can promote weight loss by triggering the use of fats stored in the body (2).

Intermittent fasting involves eating fewer meals, which reduces the calorie intake of a person. Unless the person compensates for the reduced number of meals by overeating during the phase of food intake (typically you won’t), the overall calorie consumption of a person stands reduced.

Intermittent fasting also causes reduced insulin production, increased growth hormone secretion (up to 5x normal amounts), and increased norepinephrine levels all of which support the breakdown of fats to be used as energy (3) (4).

Fasting is a quick way to lose weight

May help prevent cancer

Fasting slows down the rate of cell growth, and stimulates autophagy, the body’s clean up mode. Both of these effects may help to reduce the growth of cancers, or even eliminate small tumors and pre-cancerous cells. Conclusive human studies are still needed but the results in animals appear promising.

In one study a group of rats were infected with tumors, 50% of those on calorie restriction survived 10 days later, whereas only 13% of those with normal diets survived (5).

In addition, fasting during chemotherapy treatment seems to reduce the side effects of chemotherapy. This works because chemotherapy targets rapidly dividing cells. During fasting cell division slows down, this slowing effect is far more pronounced in regular tissues than in cancer cells. Thus the chemotherapy is able to better target cancer cells while affecting fewer healthy cells (6).

Improves organ and brain health

Intermittent fasting can improve the health of vital organs including the brain, heart, liver, and kidneys, thereby improving longevity. For example; research studies have revealed that intermittent fasting can improve the risk factors for heart attacks such as hypertension, inflammatory markers, cholesterol and triglycerides levels, and blood sugar levels (7).

It can also slow down the degenerative changes in the brain and improve cognitive functions such as memory, attention span, and problem-solving skills. It may reduce the risk of degenerative brain disorders like Alzheimer's disease, and dementia and thus, improve longevity (8).

Fasting can help protect our brains from degenerative diseases like dementia

How else does it benefit longevity, at a cellular level?

Improved cellular clean up processes

Our cells incur a huge amount of DNA damage on a daily basis. This is caused by environmental factors such as solar radiation and pollution, by-products from our metabolism such as free radicals, and the DNA replication itself is prone to error.

Fortunately, our bodies can repair damaged DNA. One method of DNA repair is via the sirtuin proteins. Sirtuins are a family of proteins that assist in DNA repair. They are activated when the body senses it is in a stressed state (e.g. fasting). Activating the sirtuins accelerates the DNA repair processes in our bodies.

Fasting also stimulates a cellular detoxification processes known as autophagy (9). Autophagy is the body's way of cleaning out cellular trash to restore the health and functioning of cells. This cellular trash if left uncleared can lead to inflammation and even cancer.

Every day our DNA incurs millions of DNA strand breaks, which need to be repaired

Improved mitochondrial functions

A research study conducted by Harvard researchers has shown that intermittent fasting could increase lifespan by slowing down degenerative changes in the body and delaying the effects of aging. It is believed to work by improving general health by modifying the activities of the mitochondrial network inside the body cells and tissues (10).

Mitochondria work like small power plants for our cells. Mitochondria also play a key role in the aging of the cells. The studies have shown that changing the shape of mitochondrial networks can enhance the power generating abilities of the cells and thereby improve their longevity and lifespan.

More importantly, it also illustrates that fasting could manipulate these mitochondrial networks and thus, maintain their "youthful" state (11).

Mitochondria are the power factories of our cells

Reduced oxidative stress and inflammation

Oxidative stress and inflammation in the cells can speed up the aging process.

Oxidative stress occurs due to the damage caused by unstable molecules known as free radicals. Free radicals have the ability to react with and damage other molecules such as proteins and DNA. This can trigger degenerative and cancerous changes in healthy organs. Similarly inflammation in the body can cause damage to nearby cells and DNA.

Several studies have shown that intermittent fasting could enhance the body's resistance to free radical damage or oxidative stress and reduce inflammation to slow down aging. It can also reduce the risk of cancer by protecting healthy cells against toxins and carcinogenic agents like free radicals (12).

What method of intermittent fasting seems to be the most effective?

There are several different forms of intermittent fasting, the most common approaches are described below. Ultimately, the best method of fasting is the one which works for you. Choose something you can stick to and incorporate in your routines.

Shorter fasts

Shorter fasts last for less than 24 hours. Shorter fasts are more suitable for people who are new to fasting and are not used to avoiding food intake for prolonged hours. Shorter fasts still deliver a range of benefits and can be easier to incorporate into your weekly habits.

There are two common approaches, the 16:8 and the 20:4.

In 16:8 intermittent fasting, the person should fast every day for 16 hours continuously. Sometimes, it is also called the 8-hour eating ‘window’ method. All meals should be consumed within the 8-hour time period. The 8-hour time period needs to be continuous and cannot be broken down into two or more phases.

For the rest of the 16 hours of each day you should not consume any calories. This method can be followed safely every day.

An example of 16:8 is eating all your food between 11:00 am and 7:00 pm. This would require you to skip breakfast and have an early dinner. You can eat 2 or 3 meals during the 8-hour period. You can also choose any continuous time period of 8 hours to eat depending on your routine or personal preferences.

20:4 is another form of short fasting method that involves a 4-hour window for eating and a 20-hour window for fasting. You can choose a continuous time period of 4 hours such as between 1:00 pm and 5:00 pm every day and avoid food intake for the remaining 20 hours. This would generally involve eating 1 meal or 2 smaller meals within the 4-hour period.

Shorter fasts need to be done more frequently in order to derive the expected health benefits.

24-hour fasts

A longer fast of 24 hours can be adopted by those who feel they have the capacity to go without food for a longer duration. We suggest you try a couple of shorter fasts first before working your way up to a 24-hour fast.

The 24-hour intermittent fasting involves avoiding food intake from lunch to lunch or dinner to dinner. For example; you can eat dinner on the first day, , skip breakfast and lunch the next day, then eat dinner. This form of intermittent fasting is usually done 1 to 3 times per week.

The 5:2 intermittent fasting approach is a popular form of the 24 hour fast. The 5:2 approach involves fasting for 24 hours 2 times per week, on the other 5 days you can eat normally.

Alternate-day fasting is another common approach to the 24 hour fast whereby a person fasts for 24 hours every second day. During the other days they can eat normally.

Extended fasting

This form of intermittent fasting lasts for more than 24 hours. Extended fasting is recommended only for people who have some experience with fasting and are already comfortable fasting for 24 hours. Anyone considering extended fasting should consult their doctor first to ensure they would not be at any risk while fasting.

Extended fasting involves avoiding food intake for 2 to 14 days. Fasting for more than 14 days is not advisable as it can increase the risk of refeeding syndrome, which occurs due to the dangerous shift in minerals and fluids once food is re-introduced after a long period of fasting.

It is advisable to use multivitamin supplements during extended fasting to avoid nutritional deficiencies.

Can I consume some calories when fasting?

If you find it difficult to go completely without food for 24 hours you can still achieve many of the benefits of fasting if you consume only a small number of calories during the fasting period.

This approach won’t deliver such extreme changes as fasting completely however incorporating some calories can make fasting more sustainable in the long term for many people, therefore leading to better long term results.

If you do consume calories it is important not to consume more than 800 calories in the fasting period. 800 calories should be sufficient to help avoid food cravings and reduce the risk of hypoglycemia or low blood sugar levels. The calories can be consumed as a single meal or spread throughout the day.

If you eat on fasting days, try to stick to low calorie foods which are high in fiber

How often do you need to fast?

It is only when intermittent fasting is adopted as a dietary habit over several weeks or months that a you will see real long term results, and derive benefits such as improved longevity.

If you choose the shorter fasting approach, this should be done at least 3-5 times per week. 24-hour fasts can be done 1-3 times a week. The frequency of longer fasts depends upon duration. A 48 hour fast could be done once per week but a 4 day fast should not be done more frequently than once per month.

Intermittent fasting is easier for most people to maintain than a regular diet. Start with shorter fasts and work your way up from there. Find an approach that works for you, one which you can incorporate within your routine, and stick with it. If you do you will see results.