Your Guide to Prolonged Fasting

Fasting for more than 48 hours can activate and harness cellular recycling and rejuvenation. 

With all the shorter fasting alternatives available, going two days or longer without food might seem a bit masochistic. To your body, though, these prolonged fasts are like vacations where each cell gets to take a few days off for a little R&R. Scientific research shows that prolonged fasts (48 hours and over) confer longevity and health benefits that can’t be attained through shorter fasts.

Prolonged fasting is ideal for people who

• want to lose weight
• who don’t want to change their daily eating habits but want the long-term benefits of fasting
• or who are seeking major improvements to their physical and mental health.

Doctors recommend that you ramp up to longer fasts with several short fasts over the course of a week or longer. But unless you have medical conditions like heart or liver disease that would make fasting unadvisable, prolonged fasts are perfectly safe when practiced in the correct way. Some people have gone up to a year and longer with absolutely no food!

What is Prolonged Fasting?

Prolonged fasts start with a minimum of 48 hours of fasting time and generally fall within a 2-5 day range. Other common prolonged fasts include: 

• weeklong fasts
• 10-day fasts
• and two-week fasts.

Doctors usually advise people to check in with their healthcare practitioners prior to embarking on these longer fasting journeys. And in many instances, doctors will supervise these fasts – monitoring vitals, electrolytes, and hydration levels to ensure safety.

Most prolonged fasts limit the consumption of all foods and calorie-containing beverages. However, plain coffee and non-sweetened herbal teas are allowed and will not break the fast. There is even a special type of prolonged fasting, called the Fasting Mimicking Diet, that allows you to eat 25% of your normal calorie intake for five days.

Benefits of Prolonged Fasting

Longevity

During the break from food, your body’s cells shut down growth operations and refocus their energy on repairing and rejuvenating. This process, known as autophagy, reaches its highest levels after the second day of a prolonged fast. Autophagy has been shown to repair DNA and increase the length of telomeres, which is associated with a longer lifespan.

In studies of yeast, worms, and mice, fasting demonstrably increases longevity while improving the organism’s resistance to stress. Long-term and longitudinal studies have not yet been performed on humans. But, studies have shown that several different markers for longevity increase when we fast – especially during prolonged fasts.

Mental health

Once you pass Day 1 of fasting, you start running out of a fuel reserve in your liver called glycogen. That’s when the body is forced to find an alternative fuel source for your organs and brain. It does this by converting fat into sugar through the process of gluconeogenesis, and also through the production of ketones (ketogenesis), which are especially useful to the brain.

Elevated ketone levels have been demonstrated to improve the symptoms of epilepsy and Parkinson’sdisease. Scientists also consider prolonged fasting as ‘neuroprotective’, and it’s been shown to reduce depression while enhancing mood.

Cancer

Fasting is thought to reduce the risk and spread of cancer by lowering the levels of insulin and insulin-like growth factor 1 (IGF-1), which both feed tumors. These growth factors are reduced by up to 90% during a prolonged fast. Fasting has also been shown to improve the efficacy of chemotherapy in the treatment of cancer.

Weight loss

Studies show that prolonged fasting is an effective way to lose weight. Fasting differs from other forms of calorie restriction or dieting, though, because it substantially lowers insulin levels. Experts say that this changes the body’s ‘set point’, which prevents rebound weight gain. 

Risks of Prolonged Fasting

While there certainly are more risks to prolonged fasting than any other type of fast, these are nothing to be concerned about if you prepare for the fast and consult your doctor. Typical risks include the following:

• dehydration
• electrolyte imbalance
• hypovolemia
• fatigue
• dizziness
• feelings of fainting
• headache
• and hypertension.

People commonly experience irritability and low-energy during prolonged fasts because the body is transitioning from using carb-containing foods for energy to just your body fat. 

How to Do Prolonged Fasting?

More than any other fast, caution is advised with prolonged fasts. Seek your doctor’s advice before you start. And if you plan on fasting for three days or over, consider having your doctor participate in a supervised fast.

The next step is to prepare for your prolonged fast.

Your ability to fast for longer periods of time is dependent on how effective your body is at producing ketones. That’s why doctors recommend practicing intermittent fasts of 12-20 hours in the week or month before a prolonged fast; this trains your metabolism to burn fat for fuel, which will keep your brain from ‘bonking’ before you’ve even gotten into Day 2. If you haven’t done a prolonged fast before, stick with the two-day fast. Or you can try the Fasting Mimicking Diet, which allows you to eat around 500 calories per day for five days.

Once you’ve prepared for your fast, you’ll want to follow these steps:

• add ½-1 tsp of sea salt in your morning water to prevent electrolyte depletion.
• consume more water than you normally would.
• rest frequently – listen to your body.
• keep yourself busy throughout the day so that you don’t focus on your hunger
• if you feel unwell, stop. Hunger is normal, but illness is not.
• if you stop losing weight, quit your fast.
• break your fast with very small quantities of food (i.e: a handful of nuts, or a piece of bread.) Wait an hour or two, and then have a small-sized normal meal. Focus on light foods for the first day back to eating.