Why choose to fast two days a week? Compared to other fasting methods?

Why choose to fast for two days each week?

Fasting is not a new phenomenon in human history; many religions have traditions related to it, and the ancient Chinese also frequently used the method of "Bigu" (辟谷) for health preservation. There are two main methods of fasting: long-term fasting and intermittent fasting. Intermittent fasting can be further varied, such as the alternate-day fasting and two-day fasting described below. This book argues that two-day fasting is more in line with modern lifestyles and can achieve relatively better weight loss and health enhancement effects.

**Four days of fasting**

Many countries have a tradition of fasting. Russians enjoy challenging fasts, where they completely abstain from food, only drinking water, taking cold showers, and exercising. Germans, on the other hand, prefer gentler fasts, consuming about 200 calories a day. For longer fasts such as a four-day fast, expert guidance is required throughout the process, or one should seek guidance from a specialized fasting institution.

Significant changes occur in the body during the first 24 hours of fasting. In the first few hours, the glucose circulating in the blood is depleted. If not replenished by food, the body will utilize glycogen, which is glucose stably stored in muscles and the liver. Only after glycogen is depleted will the body begin burning fat. This fat-burning process involves the breakdown of fatty acids in the liver, producing a substance called ketone bodies. The brain uses ketone bodies instead of glycogen as an energy source. You may experience discomfort during the first two days of fasting because the body and brain must switch from the familiar glucose and glycogen as fuel to ketone bodies. Because the body is not used to using ketone bodies, headaches, insomnia, and dizziness may occur. By the third day, the body alleviates these discomforts through hormonal regulation. After a four-day fast, tests show a decrease in body fat, blood sugar, and IGF-1 levels.

Besides being difficult to follow, the four-day fast also has the drawback of short-lived effects. Once you return to your normal lifestyle, your body will gradually return to its previous state. People who fast for a long time will not only lose fat but also muscle unless they combine fasting with active exercise.

**Alternating-day fasting**

Alternate-day fasting is one of the most widely studied short-term fasting methods internationally. It involves abstaining from food or consuming only a small amount of food every other day, while eating freely on the non-fasting days. Researchers have found through experiments that strictly adhering to alternate-day fasting can achieve excellent fat loss results, even when consuming high-fat foods on non-fasting days. It also lowers LDL cholesterol and blood pressure, indicating a reduced risk of cardiovascular disease, heart disease, and stroke.

Another advantage of alternate-day fasting is that it doesn't reduce muscle mass, whereas typical calorie restriction diets tend to lead to muscle loss. The real challenge of alternate-day fasting lies in the influence of lifestyle and social environment. For working professionals and those living with family, fasting every other day can cause social and family relationship problems.

**Two-day fast**

Unlike alternate-day fasting, two-day fasting requires choosing only two days a week to fast, and preferably two fixed days, such as Monday and Thursday. This makes it easy for family, friends, and others to figure out which day is your fasting day, reducing social inconvenience.

How effective is two-day fasting? Scientists conducted an experiment with 115 female volunteers, dividing them into three groups. One group followed a Mediterranean diet of 1500 kcal per day, avoiding high-fat foods and alcohol; another group fasted for two days, eating normally five days a week and following a low-carbohydrate diet of 650 kcal on the other two days; the last group also fasted for two days a week without carbohydrates, but without restricting total calories. After three months, the women in the second group who fasted for two days had the greatest average weight loss (4 kg), almost twice that of the group that restricted calories throughout (the first group), who only lost an average of 2.4 kg. Therefore, compared to daily dieting, two-day fasting is not only easier to implement but also more effective.

How to choose a reasonable "fasting day"?

The most sustainable approach is to choose two non-consecutive days each week for fasting, consuming 500-600 calories on those days, divided between breakfast and dinner. This fasting pattern is called intermittent fasting, also known as the 5:2 diet, which consists of 5 days of normal eating and 2 days of intermittent fasting. Most of the time, you can eat happily without having to count calories.

The most reassuring aspect of intermittent fasting is that you don't have to "cut back" your food intake every day to lose weight. It's not a "deprivation" diet, making it relatively easy to follow. On fasting days, the thought of being able to eat normally the next day, and the fact that each fast is just a temporary farewell to food, provides the motivation to stick to it. On fasting days, you don't have to think about fasting at all; you can still enjoy food and participate in daily gatherings with family and friends. There's no need to specifically choose low-fat foods, there are no complicated rules, and you don't need to constantly remind yourself, "No, I'm on a diet, I can't eat." Therefore, intermittent fasting is by far the easiest weight loss method to maintain.

Since everyone's needs, daily routines, family circumstances, determination, and preferences are different, the choice of fasting days can be determined according to your specific situation. For example, this book recommends setting Monday and Thursday as fasting days. Of course, you can also choose Wednesday and Sunday, or Tuesday and Saturday, etc. If you find it easier to fast on weekends, choose one of them as the weekend. There is no specific requirement for the interval between two fasting days; it depends entirely on personal preference. However, for most people, fasting for two consecutive days is by no means easy. Therefore, generally speaking, it is more reasonable to leave a few days of buffer between two fasting days.

Before embarking on intermittent fasting, ladies should calculate their menstrual cycle and selectively avoid fasting days during the three days preceding their period. During menstruation, maintain a normal diet and avoid raw or cold foods.