Intermittent Fasting vs. Extended Fasting: Impacts on Longevity



Fasting has been an integral part of many cultures and religions for centuries. However, only recently has it garnered mainstream attention in the health and fitness world. Fasting, in its most basic form, is the intentional abstention from calorie consumption for a set period. Today, we have numerous variations of fasting, including intermittent and extended fasting.

The health benefits of fasting are increasingly being backed by scientific research, one of which includes its potential impact on longevity. In this post, we will delve deeper into intermittent fasting versus extended fasting, and their respective effects on lifespan extension.

What are Intermittent Fasting and Extended Fasting?

Before we explore the impacts on longevity, let’s understand what these fasting methods are and how they differ.

Intermittent Fasting (IF)

Intermittent Fasting (IF) involves alternating cycles of eating and fasting. While there are several types of IF, the most popular ones include the 16:8 method (fasting for 16 hours a day and eating only during an 8-hour window), the 5:2 (eating normally for five days and restricting calorie intake for two days) and the ‘eat-stop-eat’ approach where a 24 hour fast is undertaken once or twice a week. This form of calorie restriction has become popular for weight loss, metabolic health, and as a potential life-extending practice.

Extended Fasting

On the other hand, extended fasting involves not eating for a more prolonged period, usually between 24-72 hours or even longer. This type of fasting is often undertaken for deep cellular cleansing, spiritual or religious reasons, or as a forced scenario due to illness or surgery.

It’s worth noting that both types of fasting should include non-caloric liquids like water, unsweetened coffee and tea to maintain hydration.

Fasting and the Biological Mechanisms of Longevity

Many of the benefits of both intermittent and extended fasting are linked to an intricate biological process known as autophagy. Autophagy, from the Greek ‘self-eating,’ is essentially a recycling program for cells, aiding the removal of dysfunctional components and rebuilding them anew. Boosting autophagy through fasting can lead to numerous health benefits like enhanced immunity, decreased inflammation, protection against neurodegenerative diseases, and, notably, increased lifespan.

Further, fasting also prompts the body to shift its energy source. In the absence of incoming food, the body starts burning stored fat and producing ketones for energy, inducing a metabolic state known as ketosis. This metabolic shift has been associated with numerous health benefits, including weight loss, cognitive enhancement, and increased lifespan.

Intermittent Fasting and Longevity

While research on humans is still emerging, several animal studies have associated IF with increased lifespan. A study published in Cell Metabolism revealed that rats that underwent IF lived 36-83% longer than those that did not. Another published in the Journal of Nutritional Biochemistry found that IF boosted the longevity of fruit flies.

The possible longevity effects of IF are likely due to improved metabolic health, reduced inflammation, and increased autophagy. Moreover, IF has been linked to improved insulin sensitivity, lower blood pressure, reduced cholesterol levels, improved heart health, enhanced brain function, and neuroprotection, all of which could contribute to a longer, healthier life.

Extended Fasting and Longevity

Just like IF, extended fasting is also associated with the potential for longevity, albeit with markedly different mechanisms. Extended fasts tend to go beyond the mere shift to burning stored fat for energy and push the body towards deeper states of autophagy and detoxification.

A study in Cell Metabolism noted that extended fasts (2-4 days) could essentially ‘reboot’ the immune system, shedding damaged immune cells and generating new ones. This rejuvenation of the immune system may contribute towards longevity. Furthermore, extended fasting has been associated with lower risks of cancer, cardiovascular diseases, diabetes, and neurodegenerative disorders, again, all of which point towards potential lifespan extension.

Intermittent vs. Extended Fasting for Longevity: Which is Better?

Both IF and extended fasting promote biological processes that could potentially lead to increased lifespan. However, determining which method is ‘better’ for longevity isn’t straightforward and largely depends on individual lifestyles, health status, and goals.

IF might be more suitable for everyday lifestyle integration, where daily calorie restriction can lead to consistent health benefits coupled with the potential for longevity. Further, there’s also some evidence to suggest that frequent, regular bouts of fasting, as seen in IF, may potentially have more consistent impacts on lifespan extension.

Extended fasting, with its deeper periods of autophagy and detoxification, might be effective for periodic ‘resetting’ of the body. However, it is more intense and may be more challenging for many people to undertake or sustain regularly.

Most importantly, regardless of the type of fasting one might choose, it should be conducted safely and preferably under the supervision of a healthcare provider, especially for those with existing health conditions.

Final Thoughts

While the exact impact of fasting on human longevity is not yet fully understood, growing evidence suggests that both intermittent and extended fasting could play a role in lifespan extension. These methods can promote autophagy, improve metabolic health, enhance cognitive function, and lower risks of various diseases – all of which are potentially conducive to a longer, healthier life.

However, it is crucial to remember that whilst fasting may indeed hold the key to improved longevity, it is merely one piece of the puzzle. A balanced diet, regular physical activity, adequate sleep, and a healthy lifestyle are all equally, if not more, important pieces in achieving optimal health and, ultimately, longevity.


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