Fasting has gained attention for its potential to improve longevity by promoting cellular repair, reducing inflammation and optimizing metabolic health. The roots of fasting as a therapeutic practice trace back to many cultures, religions, and health traditions, where it has long been used as a natural means to heal and rejuvenate the body, and as a ritual for mental and emotional clarity.
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Fasting has gained attention for its potential to improve longevity by promoting cellular repair, reducing inflammation and optimizing metabolic health. The roots of fasting as a therapeutic practice trace back to many cultures, religions, and health traditions, where it has long been used as a natural means to heal and rejuvenate the body, and as a ritual for mental and emotional clarity.
Physiological Stages of Fasting
During fasting, the human body undergoes physiological changes as it shifts from using glucose as the primary energy source to relying on fat reserves and ketone bodies, a process that can bring various health benefits. Depending upon the metabolic changes, fasting may be categorized into the following phases:
Post-Absorptive Phase (4-8 hours)
When the body fully digests food and uses glucose from recent meals as energy. In this phase, blood glucose levels balance and so do insulin levels. This phase plays a foundational role in fasting, as it primes the body for later stages, where more intense metabolic changes occur, further enhancing health and longevity benefits.
Glycogen Depletion Phase (8-24 hours)
With no new food intake, the body shifts to glycogen stores in the liver and muscles for energy. As the body uses stored glycogen, blood sugar levels stabilize. Lower insulin levels can promote fat burning, which supports weight management and insulin sensitivity. The glycogen depletion phase marks the body’s transition from relying on stored glucose to beginning more intense fat utilization and ketone production, setting the stage for deeper metabolic changes in extended fasting.
Gluconeogenesis & Fat Burning (24-48 Hours)
After glycogen stores are depleted, the liver starts converting amino acids and glycerol into glucose. Simultaneously, the body ramps up fat breakdown, using fatty acids for energy. Increased fat metabolism can aid in weight loss. In this phase, the body initiates autophagy – a process where cells digest and recycle damaged components due to the absence of new nutrient inputs. This cellular “clean-up” can potentially reduce the risk of certain diseases and support overall health and longevity.
Ketosis (48-72 hours)
In this phase, ketone bodies become the primary energy source as the liver converts fatty acids into ketone bodies. Ketones have neuroprotective effects and can help protect the brain. Mental clarity often improves, and inflammation may reduce, potentially benefiting conditions like arthritis or autoimmune diseases.
Protein Conservation Phase (Beyond 72 hours)
The body fully shifts to fat and ketones for energy, conserving protein to prevent muscle breakdown. Extended fasting can promote deep cellular repair and boost cell production, potentially aiding in tissue regeneration and immune system renewal.
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How Does Fasting Slow the Aging Process?
Research suggests that fasting and calorie restriction can slow some of the biological mechanisms of aging and support overall health.
- Reduction in Oxidative Stress: Fasting reduces the production of free radicals and oxidative stress, which are primary contributors to cellular aging. Using stored fat for energy produces fewer reactive oxygen species (free radicals). Fasting also boosts mitochondrial function, making energy production more efficient and generating fewer free radicals as a byproduct. Lower oxidative stress can minimize DNA damage and slow the aging process.
- Autophagy Activation: During fasting, the body initiates autophagy, a “cell-cleaning” process that removes damaged cellular components and recycles them. This promotes healthier cells, reduces inflammation and combats age-related diseases.
- Improved Insulin Sensitivity: Fasting enhances insulin sensitivity and stabilizes blood sugar levels, lowering the risk of diabetes and other metabolic syndromes, which are linked to accelerated aging.
- Reduced Inflammation: Regular fasting has been shown to decrease inflammation markers. It positively impacts immune function, metabolic process and cellular repair. Lower insulin levels, reduced production of pro-inflammatory cytokines, enhanced ketone production and reduced visceral fat all lower the inflammatory changes in the body.
- Hormone Regulation: Fasting impacts levels of hormones such as growth hormone, which plays a role in tissue repair and muscle maintenance, and may slow the decline of these functions with age.
- Telomere Protection: Some studies suggest that fasting can reduce the rate of the shortening of telomeres (the protective caps at the ends of chromosomes made up of repetitive DNA sequences) and therefore potentially extend cellular lifespan.
Types of Fasting
Below are some popular forms of fasting.
Intermittent Fasting: A period of eating that alternates between periods of fasting and eating. Common methods include:
- 16/8 Method: Fasting for 16 hours and eating within an 8 hour window.
- 5:2 Diet: Eating normally for five days and restricting calorie intake on two non-consecutive days
Extended Fasting: Fasting for periods longer than 24 hours, such as 48 hour or 72 hour fasts, often with water only or other clear non-caloric liquids. This should be done carefully and ideally under guidance.
Therapeutic Fasting: Therapeutic fasting is a structured approach used for various health conditions and should be performed under the supervision of an expert. According to Naturopathic principles, “Fasting doesn’t cure the disease, but creates the environment to heal." Therapeutic fasting includes periods of light or limited foods, such as liquids and fruits, focusing on restoring balance. This practice promotes healing, detoxification, and overall health improvement, varying based on specific health conditions and individual constitutions. Therapeutic fasting is increasingly recognized for its potential benefits and is often integrated into holistic health practices.
While fasting isn’t a single solution for aging, its effects on cellular repair, metabolic health and inflammation show promising benefits for longevity and healthy aging.
Arun K. Tomson is a naturopathic physician and director of AyurMa at Four Seasons Resort Maldives at Landaa Giraavaru, where he heads an expert team in creating bespoke therapeutic programs that unite Ayurveda, yoga, planetary well-being and wellness. Tomson helps individuals discover their body’s ability to heal through diet, exercise and natural treatments.
