Hello,
autophagy is a natural process of cellular renewal that is being discussed increasingly often today, especially in connection with ageing, metabolic health and fasting. It is not a „biohack“ but a fundamental mechanism that determines how well our cells can regenerate and build metabolic resilience.

In this edition, we will explain why autophagy is so important, how it relates to metabolic flexibility, why not only what we eat but also when we eat matters, what the limits of current knowledge are, and above all, how it relates to fasting.

Why is autophagy talked about so much?

Autophagy has been a major topic of discussion in recent years, and rightly so.
Why?
It is the process by which cells break down and recycle their own damaged or surplus components. If it does not function properly, damaged proteins and dysfunctional organelles accumulate in cells, leading to degenerative changes and a higher risk of many chronic diseases. It therefore affects not only health but also longevity, because the so-called autophagic potential - the ability of cells to carry out their own maintenance effectively - often declines with age. Cells thus gradually lose part of their regenerative capacity and cope less well with cellular stress.

This raises a key question: what actually determines when this cellular clean-up is activated and how intensely it takes place?
The answer brings us to the broader concept of metabolic flexibility. It refers to the body's ability to switch flexibly between energy sources - primarily using glucose after meals and more fats and ketones between meals and after longer periods without food. Imagine the body as a smart system constantly monitoring the state of its reserves. Cells have their own metabolic sensors that assess whether the environment is in a state of abundance or, conversely, scarcity:

In a state of abundance - after a meal - signals of growth and storage predominate. The body builds, synthesizes and stores energy.
Once the energy supply declines - between meals, during physical activity or after a longer interval since the last meal - signals of maintenance and recycling begin to predominate.

Autophagy enables cells to switch from a growth mode to deep maintenance, increasing their resilience and ability to survive demanding conditions. At the cellular level, what matters is how long and how often the body is in a state of abundance and how often we allow it to move into a maintenance mode.

This is where dietary patterns come into play. In the modern environment, it is common to eat from early morning until late evening, often without significant breaks. Breakfast, a snack, lunch, another snack, dinner - with small „nibbles“ in between. Metabolically, this means that the body spends most of the day in a state of abundance, with repeatedly elevated insulin levels and a predominance of anabolic (growth) signals. The room for deeper regenerative processes is relatively limited.

From this perspective, interest in various forms of fasting makes sense:
Intermittent fasting and time-restricted eating work on a simple principle: shortening the time window during which we consume energy and extending the period without food. Typical examples include a 16:8 regimen (16 hours without energy intake and an 8-hour eating window) or finishing food intake earlier in the afternoon. From a metabolic perspective, this means a longer part of the day during which insulin levels fall, glycogen stores are depleted and the body gradually uses more fat as an energy source. In this environment, signalling pathways associated with cellular maintenance, including autophagy, are activated.

However, we should be careful not to oversimplify this principle in practice. The effectiveness of IF or TRE does not lie in „magically switching on“ autophagy after a certain number of hours. Studies show that, in terms of weight reduction and improvements in cardiometabolic markers, these approaches are often comparable to conventional continuous energy restriction. Their benefit lies mainly in helping some people regulate their energy intake better, reduce overeating and stabilize their daily routine.

An interesting variation is so-called early time-restricted eating, meaning that most energy is consumed in the first half of the day. This approach better respects the circadian rhythms of metabolism - insulin sensitivity and the ability to process glucose are usually higher in the morning than in the evening. Studies here show improvements in insulin sensitivity, blood pressure and appetite regulation even without significant weight loss.

Alongside shorter regimens, there are also multi-day fasts. These represent a more significant metabolic intervention for the body, involving deeper changes in energy metabolism, higher ketone production and more intensive activation of adaptive mechanisms. Experimental studies (especially in animals) show that longer fasting can significantly stimulate autophagic processes. In humans, however, direct measurement of autophagy is methodologically challenging and the evidence remains more limited.

From the perspective of autophagy, fasting can indeed act as a strong stimulating factor. The key point, however, is that it is not an end in itself. The aim is not to maximize autophagy, but to support metabolic flexibility and allow the body to move regularly between growth and maintenance modes.
Fasting can therefore be autophagy's „best friend“ - not because it is a universal solution, but because it creates a metabolic environment in which cellular maintenance has a chance to occur naturally.

Autophagy as a foundation of cellular balance

Autophagy is a fascinating process that plays a major role in how quickly we age, how our metabolism functions and how well our immune system performs. If we want to influence our health consciously and effectively, we must first understand how this internal cleansing process actually works.

Read the article

Tip do praxe:

What you can do right now

Establish a regular overnight break from food.
12 hours without energy intake (for example, dinner at 7:00 p.m. and breakfast at 7:00 a.m.) is a safe and realistic starting point for most people. It gives the body daily room to transition from storage to maintenance mode.
Limit constant „snacking“ during the day.
Frequent small portions keep insulin levels persistently elevated and can dampen natural regenerative processes. Clearly defined meal times help stabilize the metabolic rhythm.
Include regular exercise at least 3× per week.
A combination of strength and endurance training supports metabolic flexibility and the quality of muscle tissue. Physical activity also increases insulin sensitivity and improves the use of fat as an energy source.
Make sure you get enough sleep.
Chronic sleep deprivation increases stress hormones and can disrupt regenerative mechanisms. Quality sleep supports hormonal balance and metabolic stability.
Prefer minimally processed foods.
More stable blood glucose levels and a lower inflammatory burden create a more favourable environment for cellular renewal. A balanced intake of protein, fibre and healthy fats also helps maintain a feeling of fullness for longer.

Is it necessary to fast for a long time to activate autophagy?

Question:

Is it necessary to fast for a long time to activate autophagy?

Answer:

The short answer is: in most cases, no. Autophagy is a physiological process that occurs continuously in the body, and its intensity changes dynamically according to the cell's energy status. Even a regular overnight break from food is a metabolic signal during which insulin levels fall, liver glycogen stores are depleted and the body gradually shifts towards greater fat utilization. This alone creates conditions for activating adaptive mechanisms, including autophagic pathways. Longer fasts can deepen these processes because they involve a more pronounced and prolonged energy deficit.

Under experimental conditions (especially in animals), longer fasting has been shown to lead to significant activation of autophagy. In humans, however, the situation is more complex. Direct in vivo measurement of autophagy is methodologically challenging, and it is not possible to determine precisely when autophagy becomes markedly activated. In practice, we therefore work more with indirect metabolic indicators than with direct measurement of autophagic activity.

Potential risks must also be considered. Multi-day fasts can lead to loss of muscle mass, increased fatigue or disruption of hormonal balance, especially if they are not conducted under professional supervision or adapted to the individual's health condition. They may be unsuitable for some groups, including older adults, people with chronic illnesses or those with a history of eating disorders.

From a professional perspective, it makes the most sense to start with shorter, sustainable regimens and consider any longer fasts individually, taking into account health status and the overall lifestyle context. When set up appropriately, both short and longer fasts can be a meaningful tool for supporting metabolic flexibility and, in turn, cellular regeneration.

I had the honour of accepting an invitation to the Longevity podcast of Hospodářské noviny. The editor and I spoke openly about the major impact that industrially processed foods have on our health and why their excessive consumption is problematic in the long term. We also discussed the phenomenon of „protein mania“ - the question of how much protein we really need and where a sensible recommendation turns into a marketing extreme.

The discussion also touched on an anti-inflammatory approach to nutrition, practical principles for working with a diet, and of course the topic of autophagy in connection with fasting.

If you would like to look at these topics in a broader context and hear specific arguments and practical examples, I believe the interview will give you further food for thought.

Listen to the podcast

Mgr. Martin Jelínek

After writing and publishing two cookbooks, I started to further deepen my education in the field of nutrition, and when I was searching for a suitable nutrition course, the ATAC course caught my attention with its good recommendations. Its length and structured content appealed to me. This is not common, especially in Slovakia, where nutrition consultant courses are generally quite superficial and short. I was looking for something more. Mr. Jelínek's courses offered me precisely what I was looking for. The course was systematic and excellently crafted to provide a solid foundation on which I could continue to build. The broad scope of the study gave me the understanding that nutrition is highly individual and not black and white. Albert Einstein said: "The important thing is not to stop questioning." I consider this truth crucial when studying nutrition. Studying with humility and constant questions at the end of sentences ensures that nutrition does not become just a theory but, on the contrary, a living whole where we primarily consider the individuality of each person.

The duration of the nutrition course is a huge plus for allowing the information to settle in the mind, deepened by additional study, and enabling us to piece it together like a puzzle. Besides the rich theory, I see the ZOF application as a significant advantage, where we almost daily created model meal plans for a wide range of clients with different needs. Therefore, the course was also practical, which every student will appreciate.

The state-authorized exam was an excellent verification of my knowledge and a confirmation that the ATAC course is truly well-designed and comprehensive enough to master this exam, which is not yet available in Slovakia. It was also a starting point for further studies that I began. The GAPS protocol and working in child nutrition fascinated me so much that I delved deeper into the study of this protocol. Our gut microbiome is closely linked with our immunity and health, both physical and mental, influencing our cravings, mood, and hormones. It is worth taking care of it.

I am immensely grateful to Mr. Jelínek for his humanity and professionalism, his openness and diligence, his personal approach, and his valuable advice.

Bc. Mária Šimková
https://mariasimko.sk

ATAC spol. s r.o.
Obrovského 2138/12, 710 00 Ostrava