Prolonged Fasting for Health & Longevity

woman standing on a beach flexing both her arms

Hunter Bennett

Throughout history, there has been one thing sought above all others. Something that has constantly re-appeared in a variety of different stories, religions, and mythologies. A thing that many have looked for, and none have found.

Eternal life.

Whether it be the fountain of youth, the philosophers stone, of the elixir of life, it doesn’t matter – man has long been searching for a way to prolong the lifespan and stave off death for as long as humanly possible.

Now, I realise that many would deem this to be nothing more than a pipedream, and I would have to agree.

Living forever is highly unlikely (read: nigh impossible).

However, there is some evidence to suggest that there may be certain strategies we can employ to potentially to extend the lifespan.

One of which is prolonged fasting.

What is prolonged fasting?

Prolonged fasting is pretty much exactly what it sounds like – a lengthy period of not eating.

Also known as ‘multiple day fasting’ and ‘periodic fasting’, prolonged fasting essentially describes a period in which you abstain from consuming any calories at all. This means no solid food and no beverages that have caloric content.

These types of fasts have appeared for thousands of years in certain religious settings, where they were thought to enhance soul and spirituality – although in modern day, they are becoming increasingly common for their impact on health.Man Sprinting Up Stairs

Prolonged vs Intermittent Fasting

Now, it is important to note that prolonged fasting is quite different from intermittent fasting.

Intermittent fasting describes a way of fasting within the day, where you essentially extend your overnight fast by a few hours to elicit a hormonal response.

While this type of fasting is great for weight management, it may not really achieve the health responses we are going to be talking about today with prolonged fasting.

Related Article: The Effects of Exercising On a High Fat Diet

How to do prolonged fasting

The process for prolonged fasting is pretty simple.

Allocate yourself a block of time lasting anywhere between 24 and 96 hours (some people may choose to go even longer…), and don’t consume any calories within that time period. Obviously, if you have never done this sort of thing before, then I would recommend starting with 24 hours, and then slowly increasing in length over each subsequent fast until you find your own sweet spot in terms of time.

During the fasting period, the idea is to keep your caloric intake to zero. This means if you feel the desire, you can still consume some zero calorie beverages, such as water, black coffee, and green tea, but that is about it.

While this sounds pretty intense, you need to understand that this type of fast is thought to be best implemented only 1-2 times per year – so it isn’t something you do all the time.

How does prolonged fasting affect health and longevity?

This is the big one – this type of prolonged fasting has been suggested to cause large improvements in health and longevity.

And just to be clear, I mean large improvements.

There is reason to believe that the implementation of one or two prolonged fasts per year can improve the health and function of both your cardiovascular and metabolic systems, and even help prevent the onset of cancer (Goldhamer, 2002; Horne, 2013; Brandhorst, 2016).

Maybe I should have said huge improvements…

Now, the reason that these improvements in health are thought to occur is due to a cellular process known as autophagy (Bagherniya, 2018).

Autophagy describes the process where old and damaged cells are broken and reused to create new healthy cells. As you can imagine, these new cells function much more efficiently than their older counterparts.

During a period of prolonged fasting, the body no longer has a flux of nutrients coming into the body. However, it still has a dire need to build and regenerate new cells.

As a result, to accommodate this lack of nutrients, it actually upregulates autophagy throughout the entire body, in which it finds these required nutrients from all of its old and damaged cells.

This results in the body functioning better, which comes with obvious improvements in health.

Amazingly, through this process, fasting has even been suggested to increase the lifespan.

By causing global improvement in cell health, and removing old and damaged cells, it is thought that the fasting process can essentially slow down the aging process at a cellular level.

While there is obviously no long-term research to support this claim, there is enough early evidence to suggest it as a possibility (Hansen, 2018).

Prolonged fasting and weight management

As I am sure you can imagine, prolonged fasting also has the ability to help you lose weight.

During a prolonged fast, your body upregulates autophagy, which is a process that naturally requires energy. Obviously, this energy has to come from somewhere, which is most commonly from the fat cells throughout your body.

As simplistic as this may sound, its pretty much how it works.

As a result, in conjunction with its impact on health, prolonged fasting has also been shown to cause marked reductions in fat mass, while assisting in normal weight management (Horne, 2012).

Who is prolonged fasting good for?

With all this in mind, prolonged fasting appears to have merit in anyone who wants to cause global improvements in their cardiovascular and metabolic health, and those individuals who want to try and keep their cells as healthy as possible.

In this manner, it could act as an adjunct treatment to diabetes and cardiovascular disease. It may even hold a place in the treatment plans of certain cancers.

And of course, those who want to add a few years to their life might be interested in throwing in a couple of prolonged fasts each year, just to see what happens.

In each of these scenarios, it is obviously important to note that the research on prolonged fasting is in its infancy. It should never be used as a stand-alone treatment. As such, try and treat it like you would with any other diet or exercise intervention. Use it in conjunction with other evidence-based treatment methods.

Male vs female prolonged fasting

While many may argue the fact, there is reason to believe that women do respond to fasting protocol a little less favorably men.

During periods of intense calorie restriction, women can see some abnormalities in hormone secretion that can result in the disruption of the menstrual cycle, potentially indicating a decline in reproductive health.

While these effects do appear to be short term (and therefore will return to normal once regular eating patterns have been began again), it is something that requires attention.

As a result, if you are a female who is interested in trialing prolonged fasting, there is merit in commencing with a 24 hour fast and seeing how you respond. You can then increase every subsequent fast by a couple of hours (e.g. 28 hours, 30 hours, etc.) and track how you respond accordingly (Yavangi, 2013).

Although this may not appear in every individual case, it must be considered.

Related Article: FODMAPS and Exercise

What happens when you stop prolonged fasting?

So, you now know that fasting offers a heap of benefit from a health perspective, but what happens when you stop fasting?

Well, to be completely honest, not a whole lot.

The improvements in cardiovascular and metabolic health appear to be maintained for months at a time. This is the reason many people choose to do 1-2 fasts per year. Weight loss also appears to be sustained (Finnell, 2018).

Once you finish your fast, there is merit in introducing foods back into your diet slowly, as to avoid any digestive discomfort. During this time, you should also keep your fluid intake high, as this will further facilitate digestion.

Are there any long-term effects of prolonged fasting?

I have already stated that the positive health effects associated with fasting appear to be sustained well beyond the fasting period. In my mind this suggests a rather positive long-term effect.

Interestingly, there is some evidence to suggest that even during extremely long sustained fasts, the body can bounce back quite efficiently without any negative long-term implications.

For example, in one study an individual maintained water only fast for a total duration of 50 days (Elliott, 2016).

Yep, that is not a typo – an entire 50 days.

This individual saw vast improvements in his metabolic and cardiovascular health. Additionally, he saw his weight drop from around 100kg all the way down to 75kg – which while quite significant. This is probably expected considering that he wasn’t consuming any calories.

One month after the fast was completed, this same individual maintained that same health benefits. He remained at a weight of 75kg and saw no significant changes in his metabolic rate.

In short, he maintained normal health.

With all this in mind, it is very unlikely that you would see any negative long-term effects associated with a mere 24 to 96 hour fast.

How does exercise play a role in prolonged fasting?

Last (but certainly not least) I wanted to touch on the role that exercise can play during a prolonged fast. To put it simply, your exercise routine should be markedly less strenuous than normal.

During a prolonged fast, you can expect your exercise performance to be slightly less than what it would be under normal circumstances. Similarly, your Manage Chronic Pain with Exerciserecovery capabilities will also be slightly lower.

This is simply because you do not have a steady influx of nutrients required to optimize energy production and recovery.

As a result, I would be inclined to steer clear of any heavy weight training during a prolonged fast. I would also avoid any high-intensity interval training.

A much better option would be to participant in some gentle low-intensity endurance exercise each day of your fast. Try exercises such as walking, cycling, or swimming. This type of exercise much easier to recover from. Additionally, it can facilitate many of the health effects associated with fasting.

So, when it comes to prolonged fasting and exercise, keep it light!

Take Home Message

Fasting has been used for thousands of years in certain religious circles. However, its health benefits are only now being realized by the health community at large. Given its huge potential, you can only expect to hear more about it in the future.

If you have ever given prolonged fasting a go (or if you would like to), then we would love to hear about it. Drop us a comment, and we will get back to you ASAP!


Goldhamer, Alan C., et al. “Medically supervised water-only fasting in the treatment of borderline hypertension.” The Journal of Alternative & Complementary Medicine 8.5 (2002): 643-650.

Horne, B. D., et al. “Randomized cross-over trial of short-term water-only fasting: metabolic and cardiovascular consequences.” Nutrition, Metabolism and Cardiovascular Diseases 23.11 (2013): 1050-1057.

Brandhorst, Sebastian, and Valter D. Longo. “Fasting and caloric restriction in cancer prevention and treatment.” Metabolism in Cancer. Springer, Cham, 2016. 241-266.

Bagherniya, Mohammad, et al. “The effect of fasting or calorie restriction on autophagy induction: A review of the literature.” Aging research reviews (2018).

Hansen, Malene, David C. Rubinsztein, and David W. Walker. “Autophagy as a promoter of longevity: insights from model organisms.” Nat Rev Mol Cell Biol 19.9 (2018): 579-593.

Yavangi, Mahnaz, et al. “Does Ramadan fasting has any effects on menstrual cycles?.” Iranian journal of reproductive medicine 11.2 (2013): 145.

Horne, Benjamin D., et al. “Relation of routine, periodic fasting to risk of diabetes mellitus. And coronary artery disease in patients undergoing coronary angiography.” The American journal of cardiology 109.11 (2012): 1558-1562.

Finnell, John S., et al. “Is fasting safe? A chart review of adverse events during medically supervised, water-only fasting.” BMC complementary and alternative medicine 18.1 (2018): 67.

Elliott, Bradley, Michelle Mina, and Chrystalla Ferrier. “Complete and voluntary starvation of 50 days.” Clinical Medicine Insights: Case Reports 9 (2016): CCRep-S39776.

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