Unlocking the Benefits of Fasting
Fasting has been practiced for centuries across cultures and religions; for some families and communities, it is a part of the normal rhythm of life.
Growing up in a Christian family, my mother fasted every Thursday as a spiritual discipline, and I adopted this practice while I was college. When I lived in the Middle East for 4 years, I joined my Muslim friends in their annual month of fasting, Ramadan. No food and no water from sun-up to sundown. I remember friends and neighbours were so generous in inviting me over for Iftah, the fast-breaking meal in the evening. It taught me that fasting together as a community with common values and goals makes this practice so much more enjoyable and sustainable.
The church in Hong Kong that our family has attended for the last 10 years has an annual fast at the beginning of January for 21 days. I am posting this blog on day 14. We are all free to fast in the way we feel works best - all sacrificing something we love and normally depend on to get through the day, whether its food or social media - all carving time out to intentionally focus on things that are a meaningful to us personally. It’s a reset button. And it’s so good for us physically, mentally, spiritually and relationally.
Fasting is often misunderstood as something strange, extreme, or impossible. Here’s a perspective shift: fasting is something we all do every day, naturally.
Think about the time between your last meal of the day and your first meal the next morning—this is an overnight fast. When you wake up and eat, you’re literally “breaking the fast.” Very simply, it is a period of abstaining from food—and sometimes drink. It allows your body to take a break from digesting food and activate biological pathways that improve health, optimise cellular function, reduce the risk of diseases and support longevity.
Different Types of Fasting
Fasting isn’t one-size-fits-all. There are several approaches to fasting, each with its own structure and benefits:
1. Time-Restricted Eating (TRE)
This is the most popular and beginner-friendly type of fasting. TRE involves eating within a specific window of time each day and fasting for the remaining hours.
Start with a 12:12 schedule (12 hours eating, 12 hours fasting).
Gradually narrow your eating window to 14:10, then 16:8, and eventually 18:6, depending on your goals and comfort level.
As a daily habit, I try to finish dinner at 8pm and not eat again until 10am the next day - fasting 14 hours and eaten within an 10-hour window.
2. Alternate-Day Fasting (ADF)
With this method, you alternate between days of normal eating and days of reduced calorie intake (typically 0–15% of your usual calories).
On fasting days, some people consume only water, tea, or broth, while others permit a small meal of 500 calories or less. Choose something nutrient dense with fibre, protein and healthy fats.
This approach can be more challenging but is linked to significant benefits for metabolic health and weight management.
3. Whole-Day or 5:2 Fasting
This approach involves fasting for one or two full days per week while eating normally on the other days.
The 5:2 method is a popular variation where you eat normally for five days of the week and consume only water or under 500 calories on two non-consecutive days.
Whole-day fasting is more intense but can be a powerful tool for resetting your body’s systems.
4. Prolonged Fasting
This involves fasting for more than 24 hours—often 2–5 consecutive days. Prolonged fasting is linked to deeper autophagy and cellular repair processes.
Historically, prolonged fasting has been practiced in religious traditions
Today, studies show that prolonged fasting can reduce the risk of chronic diseases like Alzheimer’s, cardiovascular disease, and cancer.
The Science of Fasting: Why It Works
Fasting isn’t just about skipping meals—it’s about giving your body a break from constant digestion, allowing it to focus on repair, detoxification, and optimisation. When you fast for at least 12–20 hours, your body enters a state where two key processes kick in: ketosis and autophagy.
Ketosis: The Alternative Energy State
When you eat, your body uses glucose (sugar) from food as its primary energy source. However, during fasting, when glucose levels drop, the body transitions into a metabolic state called ketosis.
In ketosis, your body burns stored fat for energy, producing molecules called ketones as an alternative fuel source.
Ketones are a “cleaner” energy source than glucose because they produce fewer free radicals, which creates oxidative stress that damages cells over time.
Ketones also cross the blood-brain barrier, providing a steady energy supply to the brain and improving mental clarity.
Ketosis typically begins 12–24 hours after fasting starts, depending on your activity level, metabolic health, and diet.
Autophagy is a process where cells degrade and recycle their own components. Damaged or unnecessary cellular material is enclosed in a membrane, forming an autophagosome, which then fuses with a lysosome. The lysosome contains enzymes that break down the materials for recycling.
Autophagy: The Body’s Cleanup Crew
Autophagy literally means “self-eating.” During fasting, your body activates this process to break down and recycle damaged cells, proteins, and toxins. Think of it as your body’s built-in detox system.
Autophagy clears out cellular debris, helping to fight aging at the cellular level.
It’s also associated with the production of brain-derived neurotrophic factor (BDNF), a protein that supports the survival and growth of new neurons.
It also induces the level of Human Growth Hormone (HGH) that supports metabolism, muscle growth and strength and reduces your risk of chronic diseases.
Autophagy typically begins to accelerate after 16 hours of fasting and peaks during prolonged fasting periods of 24 hours or more.
The Health Benefits of Fasting
The benefits of fasting extend to nearly every system in the body.
1. Longevity and Cellular Health: By activating autophagy and reducing oxidative stress, fasting helps slow cellular aging and supports longevity.
2. Enhanced Mental Clarity: Many people report feeling more alert and focused during fasting. Ketones provide a steady energy source for the brain, reducing brain fog and improving cognitive performance.
3. Reduced Inflammation: Chronic inflammation is linked to diseases like arthritis, heart disease, and autoimmune conditions. Fasting reduces inflammatory markers and promotes overall cellular health.
4. Improved Metabolic Health: Fasting lowers triglycerides, improves HDL (good cholesterol), and reduces blood pressure, all of which are markers of better heart and metabolic health.
5. Improved Insulin Sensitivity: Fasting helps stabilize blood sugar levels by lowering insulin levels and improving insulin sensitivity. This is especially beneficial for people with insulin resistance or type 2 diabetes.
Concerns and Challenges with Fasting
1. Hunger and Cravings
Most people worry about hunger. But what we often interpret as “hunger” is a mix of habit and hormones like ghrelin (the hunger hormone), which peaks at specific times during the day.
Solution: Hunger comes in waves. Keep your mind occupied, your body hydrated, and remind yourself that the sensation will pass. After a few days, your body adapts, and hunger subsides.
2. Fatigue and Low Energy
Low blood sugar and caffeine withdrawal can lead to headaches, irritability, and fatigue.
Solution: Transition gradually by reducing carbs and caffeine a few days before starting. Stay hydrated, rest when needed, and consider light exercise like walking.
3. Awkward Social Situations
Fasting can be challenging during social gatherings that centre around meals when others don’t understand your goals.
Solution: Plan your fasting schedule around family or social meals, and let people know your reasons for fasting. Encourage family members or a friend to join you when you fast.
Who Should Avoid Fasting?
While fasting is safe for most people, certain groups should avoid it or consult a healthcare professional first:
Pregnant or nursing women.
Young children and teens.
Older adults experiencing frailty or weakness.
People with current or past eating disorders.
Individuals with immunodeficiencies or chronic illnesses.
How to Start Fasting Safely
If you’re new to fasting, start small and build up gradually. Here’s how to begin:
Clarify Your Why: Understand your motivation. Are you fasting for longevity, mental clarity, or spiritual reasons? Knowing your “why” will help you stay committed.
Start with 12 Hours: Extend the time between your last evening meal and your first meal the next day. Aim for at least 12 hours of fasting and gradually increase the window.
Stay Hydrated: Drink plenty of water during your fasting hours. Herbal teas and black coffee are also good options.
Have a balanced diet with adequate protein, fats and fibre when you’re not fasting to maintain a healthy baseline that ensures successful fasts
Find a Community: Fasting with friends or joining a like-minded group can provide encouragement and accountability.
Listen to Your Body: If you feel weak, dizzy, or unwell, break your fast. Fasting should enhance your health, not harm it.
Ask your health practitioner if you have any concerns.
The Takeaway
Fasting is a powerful, natural tool for improving health, detoxification, and longevity. By giving your body a break from constant digestion, you allow it to repair and optimize itself. Whether you choose time-restricted eating, alternate-day fasting, or prolonged fasting, the benefits are undeniable—and they’re backed by science.
If you’re ready to experience the transformative effects of fasting, start small, stay consistent, and take the plunge! Enjoy the journey toward better health.
References
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Mizushima, N., et al. (2008). Autophagy fights disease through cellular self-digestion. Nature.
Mattson, M. P., et al. (2018). Intermittent metabolic switching, neuroplasticity, and brain health. Nature Reviews Neuroscience.
Longo, V. D., & Mattson, M. P. (2014). Fasting: Molecular mechanisms and clinical applications. Cell Metabolism.
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Mattson, M. P. (2019). Energy intake and exercise as determinants of brain health and vulnerability to injury and disease. Cell Metabolism.
Harvie, M., et al. (2011). The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers. International Journal of Obesity.
Patterson, R. E., et al. (2015). Intermittent fasting and human metabolic health. Journal of the Academy of Nutrition and Dietetics.
Madeo, F., et al. (2019). Caloric restriction mimetics against age-associated disease: Targets, mechanisms, and therapeutic potential. Cell Metabolism.
Nørrelund, Helene. (2005). The metabolic role of growth hormone in humans with particular reference to fasting. Science Direct
