A conversation between Thomas Paloschi, MD (founder of Longevity Incubator) and Sveva Clavarino

What is fasting?

In the eyes of scientists and physicians, a "true" fast is when you consume nothing but water for a certain period of time for health purposes.

What are the different types of fasting? 

Fasting can be categorised into different protocols such as:

Time-Restricted Feeding (TRF): 

This is by far the most commonly adopted method that involves increasing that overnight sleep fast into a longer period of fasting. 

For example, when you fast for 12 hours and eat (typically ad libitum, meaning without restrictions) the other 12 hours, it is referred to as a 12/12 Time-Restricted Fasting.

TRFs can vary in time and can extend to 16/8, 18/6, up to 22/2 periods.

The time of the day in which you decide to fast is completely up to you. Most people prefer to start the fast at around 8 pm after dinner and breaking the fast, at noon, making it a 16/8 Time-Restricted Fasting.

Intermittent Fasting (IF)

Many mistake Intermit Fasting with Time-Restricted Fasting. The first implies fasting for over 24 hours at different time periods. For example once, twice, or more per month for >24h. 

A common subtype of Intermit Fasting is the 5:2 protocol, where you fast for 2 days and eat the other 5. People who use this method tend to replace the 2 days of fasting with calorie restriction.

Alternate Day Fasting (ADF)

As the word implies, this means doing a fast every other day. For example, 24h fast followed by an ad libitum day of feeding, and then back to a 24h fast. This type of fasting is quite hard to keep up with and is commonly replaced with alternate day Calorie Restriction, where instead of fasting, you consume only 1000 calories on alternate days. 

Prolonged Fasting

A prolonged fast means that you fast for a period of time that is longer than 1-2 days. This type of fasting would need more strict monitoring by healthcare professionals. 

Fasting Mimicking Diet

This is a trademarked protocol based on the work of Dr. Valter Longo who was able to show that a 5 day controlled calorie diet would give similar benefits to fasting without having to eliminate food. Over the course of 5 days, you transition from 1000 calories on the first day to 700 calories on the last day.

What are the short and long-term benefits of fasting? 

There are three main goals one should think of when deciding if to fast:

1.     Gut Health

Fasting helps you balance the gut microbiome. Some bacteria in our gut thrive with low calories, whilst others thrive with high calories. Periods of fasting gives our gut a time to rest from food. The reduction of stress to our mucosa is especially good when suffering from intestinal diseases such as: GERD (Gastroesophageal reflux disease), peptic ulcers or other inflammatory bowel diseases.

2.     Weight Loss

According to a systematic review of 47 articles, including 27 clinical trials, Intermit Fasting shows promise as a primary care intervention for obesity.

3.     Longevity

Little is known about the long term longevity benefits of fasting in humans. Longer duration studies are needed to make significant conclusions about it. In mice and other species fasting has significantly prolonged lifespan.

Is fasting good for everyone?

No, everyone responds to fasting differently. It's a combination of genetics, health, and lifestyle that determines whether you are suitable for fasting. If you are interested in fasting, we recommend to always consult an expert.

Fasting has been discouraged for people with diabetes or people who are on medications for diabetes, people with a history of eating disorders such as: anorexia and bulimia, and pregnant or breastfeeding women unless under close supervision.

Can I drink coffee/ tea during a fast?

Tea does the trick and has no negative effects on a fast. Coffee does not break a fast but is discouraged when the goal of your fast is gut reset.

What happens to our mind and body during and after a period of fasting?

Our bodies go through different physiological changes throughout a fast:

0-3 hours: At this initial stage of fasting, our body will be processing the ingested food and will be metabolising nutrients for storage of energy usage.

4-24 hours: After 4 hours of fasting, our bodies will transition from the anabolic to the catabolic (breakdown) phase. At this stage, our body has used up all the energy from our previous meal and has started to rely on the liver for glucose (by converting glycogen to glucose). Fats starts to be mobilised and broken down to provide the liver with the precursors for ketone production. Autophagy is activated with the goal of breaking down old senescent cells to be recycled as viable proteins for energy production.

1-2 days: The liver takes over! Gluconeogenesis (the glucose producing cycle from amino acids) begins. Final stores of glycogen are being used up. Ketosis becomes the primary source of energy for the body, and especially the brain. Ketones are an excellent source of energy produced by the liver from broken-down fat. 

Not only are ketones an essential energy source for our bodies, but they have also proven to be extremely beneficial in the prevention and treatment of neurodegenerative diseases, cancers, and chronic inflammation.

3-5 days: At this stage our bodies are relying almost entirely on ketones as an energy source. Approximately 75% of the ketones produced will be used by the brain. Following a fast, our bodies will replace the old “used” cells with young and healthy stem cells.

Are there any side effects when fasting?

The most common complaints when fasting are: dizziness, weakness, bad breath, headaches, and lack of concentration. However, our bodies tend to get used to these side effects once you train your body to fast.

Bear in mind that much of the information mentioned is based on speculations and interpretations of scientific data, which might change in the future as we learn more about the human body.