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Fasting was known as "Grain Abstinence" (Bigu, 辟穀) in ancient China, a health-preserving method that involves abstaining from food and only drinking water, with the ancients seeking to prolong life through this practice. Zhuangzi-Xiaoyaoyou records "not eating the five grains." Ancient Buddhism also had the precept of not eating after noon.

People usually fear hunger and the risk of starvation, but according to surveys, an average person can survive for several months on water alone, with a few able to endure over six months without eating. The longest recorded case of fasting in scientific literature was in the 1973 "Postgraduate Medical Journal": a 207kg male, under medical supervision, went without food for 382 days, eventually reducing his weight to 82kg. Upon examination, all physiological functions were normal, and he did not regain weight. However, this is not recommended for the general public.

Is fasting really beneficial for the body?

Fasting indeed offers multiple benefits to the body, with scientifically proven advantages summarized as follows:

• Reduces inflammatory responses
• Improves brain function and slows neurodegeneration
• Lowers blood sugar in type 2 diabetes
• Avoids significant fluctuations in blood sugar
• Improves blood pressure, cholesterol, and triglycerides
• Aids in weight loss
• Delays aging
• Improves recovery from acute spinal cord injuries
• Improves immune and wind-dampness diseases, such as asthma, multiple sclerosis, and polyarthritis
• Improves side effects of chemotherapy
• Prevents cancer and improves survival rates for certain cancers

Other benefits include: improving sleep, skin, spleen qi, digestive functions, and reducing cravings and hunger for food.

The life-extending effects of fasting are widely observed across various life forms, from single-celled microorganisms to humans. Scientists have conducted experiments where various lower organisms were divided into control and experimental groups; the control group was fed regularly, while the experimental group was occasionally starved. It was found that the starved group had significantly longer lifespans (Figure 1). Similar results were found in mouse experiments, where mice that were intermittently starved lived significantly longer than those fed regularly (Figure 2).

Mouse experiments also found that starved mice had significantly fewer tumors (Figure 3); typically, middle-aged mice have significantly lower white blood cell counts than young mice, but after intermittent fasting, the white blood cell counts of middle-aged mice returned to the levels of young mice (Figure 4). Additionally, the white blood cell counts of mice undergoing chemotherapy significantly decreased, but once intermittent fasting began, their white blood cell counts gradually returned to pre-chemotherapy levels.

The reason fasting has miraculous effects lies in the fact that when food is scarce, living organisms automatically switch from "reproduction mode" to "survival mode." For example, the oxidative energy production mode in the body shifts from burning sugar to burning stored fat. Faced with the survival pressure of food scarcity, the individual's mind becomes clearer, limbs more agile, and some old tissues, useless accumulations, and waste in the body are more rapidly decomposed and absorbed by the enhanced autophagy, making the body cleaner.

Am I suitable for fasting?

In theory, everyone can fast. Before the invention of agriculture, animal husbandry, and refrigerators, which was only a few thousand years ago, humans, like other animals, relied on hunting animals and gathering wild fruits and vegetables for survival. The food supply was uncertain; one might eat a lot when lucky, or go without food for several days when unlucky. The human metabolic system was originally accustomed to an irregular eating pattern. It was only after humans invented agriculture, animal husbandry, and refrigerators that a stable food supply began, leading to the establishment of three meals a day. Humans became unable to tolerate not eating and enduring hunger, which also marked the beginning of various "diseases of affluence."

Therefore, the human body was originally designed to withstand prolonged fasting. It is "material civilization" that has caused us to lose this ability, and because we have been domesticated by material civilization for too long, modern people's bodies can no longer endure fasting for extended periods. We can only engage in gradual, short-term fasting. Prolonged adherence to Dipsacus fasting may harm health or even endanger life! Remember this!

The following groups of people are not recommended to fast: children under 12 years old, those who are underweight, weak, preparing for pregnancy, pregnant, breastfeeding, or suffering from anorexia or binge eating disorder.

Those with stomach issues, excessive stomach acid, or cholecystitis should first treat their condition before fasting.
Diabetics must fast under constant blood sugar monitoring. If blood sugar drops too low, fasting should be stopped immediately.

Those with hyperlipidemia, kidney disease, or pain wind should not fast for too long. If discomfort occurs, fasting should be paused.

How to fast?

The duration of fasting can vary, but it must exceed 12 hours to start taking effect. After 12 hours of fasting, ketone levels in the blood gradually rise, signaling the body's partial shift from "burning sugar for energy" to "burning fat for energy." It is at this point that the benefits of fasting begin to manifest.

Modern people, long accustomed to abundance, are not suited to prolonged hunger. "Intermittent fasting," also known as "light fasting," is more suitable. This involves choosing fixed periods within a day, week, or month to not eat, consuming only water or very little food. Several patterns of intermittent fasting are as follows:

• On a daily cycle, choose a continuous 8-hour window to eat normally, and only drink water for the remaining 16 hours. Advanced version: Only 6 hours, 4 hours, or 2 hours are allowed for normal eating, with water only for the rest of the time.
• On a weekly cycle, choose 1 to 2 days to eat very little or not at all, and eat normally for the remaining 5 days.
• On a monthly cycle, choose 3 to 5 days to eat very little or not at all, and eat normally for the rest of the month.

Fasting is a long-term strategy. Choose a plan that suits your health condition, schedule, work, and social life. Do not rush into fasting; start with shorter periods and gradually increase, allowing your body to adapt. If you feel unbearably hungry, your fasting is too aggressive, and you should slow down.

What to eat before and after fasting?

Eat the same amount as usual per meal, focusing on natural, minimally processed foods, and pay attention to balanced nutrition. Avoid high-calorie and junk foods.

Recommendation: 2 servings of vegetables, 1 serving of high-quality protein, and 1 serving of high-quality whole grains per meal. If you have a constitution prone to hunger, add some high-quality fats.

Do not overeat before or after fasting, as this can burden the digestive system, cause indigestion, and lead to illness.

Drink plenty of warm water, approximately "body weight (kg) × 35～40" cc. For example, a 60kg person should drink 2L～2.4L of water daily. During fasting, if you feel hungry, you can drink unsweetened, milk-free black coffee or tea, or eat sugar-free konjac to temporarily satisfy cravings.

Will fasting cause muscle loss?

Multiple studies show that intermittent fasting does not cause muscle loss in the human body and may even slightly increase muscle mass. If muscle loss occurs after fasting, it may be due to insufficient protein intake. Supplementing with high-quality protein and moderate exercise can ensure that muscles are not lost during fasting and may even become stronger.

According to a 2017 literature published by the International Society of Sports Nutrition, under low-calorie conditions, individuals with higher protein intake combined with weight training do not experience muscle loss. Another study indicates that consuming carbohydrates + protein after exercise promotes muscle glycogen recovery and muscle synthesis.

It is necessary to consume 1g of protein per kilogram of body weight each day. For example, a person weighing 60kg should consume 60g of protein per day, which is approximately the amount of protein provided by 300g of meat or 10 eggs. A small number of people may need more protein to prevent muscle loss.

Temporary discomfort during fasting

If fasting is done gradually, there is usually not much discomfort, but a few people may experience the following symptoms:

• Increased uric acid: A few people may experience pain wind or uric acid kidney stones, and should pause fasting and seek medical help.
• Chills: When the body switches from burning sugar to burning fat, thyroid function may temporarily drop sharply, causing temporary cold hands and feet, which will ease later and is not a big problem.
• Mood swings: Common in the first 3 days of fasting, may be accompanied by some symptoms of low blood sugar, which will ease later.
• Headache: The brain is used to burning sugar for energy. The low blood sugar after fasting causes the brain to switch from burning sugar to burning fat for energy, leading to temporary headaches, common in the first 3 days, which will ease later.
• Increased stomach acid: Some people may experience increased stomach acid and heartburn. If this happens, eat something. This also means that the fasting may be progressing too quickly and should be slowed down.
• Nausea when eating: This is due to the long intervals between meals and the body not being used to it. Usually, after 2-4 weeks, the body will adapt and the symptoms will ease on their own.
• Dizziness: More common when fasting for too long too quickly, such as suddenly fasting for 3 days without prior adaptation. Also, eating a large meal immediately after a long fast can suddenly reverse catabolism to anabolism, possibly causing endocrine disorders and electrolyte imbalances, leading to "refeeding syndrome," which can cause fainting or be fatal. Therefore, after a long fast, start with small amounts of food to adapt.
• Hair loss, fatigue: People who usually lose hair may have had poor nutritional status, poor or unbalanced diet before, and still eat poorly during fasting. It is recommended to eat a balanced and nutritious diet.

Initial fasting may cause some symptoms. If the situation is not serious, it usually recovers within a few days to a few weeks. If the symptoms do not ease, stop fasting immediately, consult your doctor, or wait until the body returns to normal before continuing.