Therapeutic Fasting: A Full-Body Reset That Reduces Biological Age

Have you ever considered that fasting doesn’t have to mean starving or following a religious ritual? There are many types of fasts — some can harm the body, others can be safe and deeply beneficial. Among them stands out therapeutic fasting: a guided process of renewal that helps the body activate repair mechanisms, reduce inflammation, and, according to Longevity Architect Miro Skořepa and MUDr. Michal Konštacký, Chief Medical Officer at Zenith Swiss Longevity Clinic in Prague, even slow down biological ageing.

“Fasting is not about simply stopping eating. It is a conscious, guided process during which the body switches from energy intake to using its own reserves. This metabolic switch triggers a whole cascade of positive effects — from activating cellular repair processes such as autophagy, to improving the hormonal profile, immunity, and regeneration,” explains Longevity Architect Miro Skořepa.

Fasting itself is nothing new. Across history, it has had deep spiritual roots — Christians fasted before Easter, Muslims during Ramadan, and Buddhists or Hindus have long used fasting as a path to mental balance. But they all share one principle: fasting gives both body and mind a pause. In the 20th century, science picked up this idea and began studying what happens during fasting at the cellular level.

“It turned out that what faith gave people also has strong biological meaning — the body truly uses periods without food to regenerate. Today we can consider therapeutic fasting a scientifically grounded method that supports health and longevity,” adds Miro Skořepa.

He tried its effects himself two years ago, when he hit rock bottom. At the age of 53, he struggled in an extremely demanding managerial job, weighed 40 kilograms more, his body was breaking down, he suffered from depression, and doctors were prescribing him one pill after another. He found the courage to change — and chose to live differently. His personal experience and scientific approach eventually shaped his work in longevity medicine.

For Weight Management — and for Longevity

An ideal programme for beginners is intermittent fasting. Its principle is simple: you divide the day into two parts. You consume all meals within an 8- or 6-hour eating window and fast during the rest. During the fasting period, the body depletes glucose stores and switches to burning fat.

Additional benefits include better glycaemic control, reduced average insulin levels, more energy, improved focus, and better sleep — exactly what most of us want.

Most healthy adults can also safely try a fast lasting 24 to 72 hours. Not eating for one day means a good weekly reset. Two days initiate the beginning of a cellular clean-up, though everyone should monitor their energy and blood pressure. Fasts longer than 48 hours activate deeper biological processes and must be done under medical supervision.

“Ketone bodies begin to form — an alternative fuel — and autophagy is activated, the body’s natural maintenance mechanism. During longer fasts, autophagy becomes significantly stronger, improving mitochondrial function, lowering oxidative stress and inflammatory markers. In simple terms: the body finally has time to clean and repair itself,” says MUDr. Michal Konštacký, PhD, MBA.

Every fast requires a defined preparation phase — beginning several days before fasting — and a refeeding phase, meaning the safe transition back to food. Monitoring blood pressure, pulse, hydration, and urine colour is essential.

Most mistakes happen during refeeding. “After a longer fast, digestion must relearn how to work. You must start with light foods — broths, vegetable soups, later rice or steamed vegetables. At our clinic we offer daily monitoring during the fast and follow-up care afterwards,” explains Miro Skořepa.

Fasting as a Tool for Prevention and Longevity

The modern approach to longevity isn’t about searching for an elixir of youth — it is about restoring the body’s natural ability to regenerate. Therapeutic fasting is one of the tools that activates this capability.

“Fasting is a natural part of human biology. Our ancestors routinely went through periods without available food, and the body learned to use these pauses for repair. Today we live in the opposite extreme — food is everywhere, all the time. Targeted fasting brings back the balance we have lost,” says Miro Skořepa. He adds: “Fasting is a fundamental part of a broader healthy ageing programme — connected with genetic testing, biomarkers, and lifestyle analysis. The goal is not only to live longer, but to stay healthy, strong, and vital for more years.”

Benefits of Fasting at a Glance

1. Provides a much-needed reset

• Increases insulin sensitivity — the body relearns to use energy efficiently, reducing the risk of type 2 diabetes.

• Lowers blood pressure and cholesterol — excess fat is broken down and inflammation in arteries decreases.

• Speeds up fat burning — after 24–36 hours the body enters ketosis and uses fat as its main source of energy.

• Normalises leptin and ghrelin levels — hunger and satiety hormones — helping reduce cravings and overeating.

  
  

2. Supports cellular regeneration and detoxification

• Activates autophagy — the natural “cellular clean-up” process that recycles damaged proteins and mitochondria.

• Reduces oxidative stress — lowers free radicals and increases cellular antioxidant capacity.

• Boosts immune system regeneration — during 3–5-day fasts stem cells activate and new white blood cells are formed.

• Slows ageing — similarly to caloric restriction, extends cellular lifespan and activates longevity genes (SIRT1, FOXO3).

  
  

3. Enhances mental and emotional well-being

• Increases levels of BDNF (brain-derived neurotrophic factor) — supporting new neuron growth and cognitive function.

• Improves focus and mental clarity — ketones act as a more efficient fuel for the brain than glucose.

• Helps break sugar and food dependence — resets dopamine pathways and reshapes the relationship with food.

• Calms the nervous system — reduces cortisol and anxiety, bringing a sense of inner peace.

  
  

4. Strengthens physical health and resilience

• Lowers chronic inflammation — a root cause of many lifestyle diseases (atherosclerosis, Alzheimer’s, arthritis).

• Supports gut microbiome health — helps restore the intestinal lining and microbial balance.

• Improves sleep and hormonal balance — positively affects melatonin, cortisol, and growth hormone.

• Increases human growth hormone (HGH) — after 2–3 days levels can rise up to fivefold, supporting muscle repair and fat loss.

What You Should Know

1. What is allowed and forbidden during a fast

You should drink 1.5–3 litres of clean water per day, and add calorie-free electrolytes if needed.
Avoid: caloric drinks, alcohol, honey, energy gels, and all solid foods. Ideally, also eliminate caffeine.

2. Who should not fast

Therapeutic fasting is not suitable for everyone. It should be avoided by:

• people with eating disorders,

• insulin-dependent diabetics,

• pregnant or breastfeeding women,

• individuals with severe kidney, liver, or heart conditions,

• children and adolescents.

  
  

3. Stop fasting immediately if any of the following occur

• Fainting or loss of consciousness

• Confusion

• Heart arrhythmias or strong palpitations

• Inability to keep fluids down

• Repeated cramps