Why excessive post-holiday fasting isn't true intermittent fasting

Produced by: Science Popularization China

Author: Mai Bo

Producer: Guangdong Provincial Association for Science and Technology

Recently, there has been a flood of articles online teaching people how to lose weight through intermittent fasting, encouraging everyone to replicate the diet. However, some individuals are dissatisfied with the slow weight loss from the recommended materials and have started sharing a method of eating three fruits a day. Professor Chen Chaogang, the director of the Clinical Nutrition Department at Sun Yat-sen University’s Sun Yat-sen Memorial Hospital, pointed out, "Excessive fasting is not 'intermittent fasting.' Weight loss should occur in a healthy and comfortable state; otherwise, it is easy to regain the weight!"

Intermittent fasting is a scientific method for weight loss.

Chen Chaogang stated that intermittent fasting is a weight loss method that involves strictly controlling caloric intake to decompose body fat for energy. Scientific research indicates that intermittent fasting not only effectively aids in weight loss but also reduces the risk of type 2 diabetes, improves brain health, enhances immunity, boosts gut health, and strengthens circadian rhythms. However, it does not mean "not eating anything or only consuming a small amount of food every day." Instead, it emphasizes a scientifically tailored diet based on individual circumstances, combined with appropriate exercise, especially by strictly limiting caloric intake at certain times.

"Some people online are promoting a method of losing weight by eating three apples a day, one with each meal. Does this count as intermittent fasting?" In response to the reporter's question, Chen Chaogang firmly denied, "Intermittent fasting is a scientific method for weight loss; what you're describing is extreme calorie restriction, not intermittent fasting!" He explained that there are mainly four types of intermittent fasting. The first is the 5:2 method, which is the most recommended approach. Specifically, it involves eating normally for five days a week (scientists recommend a Mediterranean diet), and then choosing two days to reduce calorie intake to 25%, meaning on fasting days, it is advised that women consume 500 calories and men 600 calories.

The second method is the 12:12 intermittent fasting approach, which involves fasting for 12 hours each day. The simplest way to practice this is to include sleeping hours within the fasting window. For instance, if dinner is eaten before 7 PM and breakfast is taken after 7 AM, then a 12-hour fast is achieved. This type of intermittent fasting does not work by reducing calorie intake; instead, it relies mainly on regulating circadian rhythms. If one eats after 9 PM, even while following the 12:12 pattern, the benefits usually associated with intermittent fasting will not be realized. This method may lead to slower weight loss results, so it is generally combined with other methods for effectiveness.

The third method is the 16:8 intermittent fasting, which restricts the fasting period to 16 hours. For example, if you have breakfast at 6 AM, dinner will be moved to 2 PM, so this method is also referred to as "no food after noon." If you start eating at 8 AM, you will stop eating after 4 PM. This approach can be challenging for many people due to the long fasting duration.

The fourth type is the alternate-day intermittent fasting method, which involves fasting every other day. On fasting days, no solid foods are consumed, and calorie intake is limited to below 500 calories, or food quantity is reduced to 25% to 30% of normal. Scientific research reports indicate that alternate-day intermittent fasting can help with weight loss and heart health in overweight adults. However, in the long term, it can be quite challenging to maintain regular alternate-day fasting.

Chen Chaogang pointed out that intermittent fasting can be adopted for a certain period, but it is not recommended for long-term use.

Weight loss should take place in a healthy and comfortable state of living.

"This Spring Festival, we had a weight loss participant who not only didn't gain weight but actually lost 4 pounds. How did he achieve this? First, he removed the skin from animal products like goose, duck, and chicken, regardless of whether he was eating at home or dining out. Second, he incorporated whole grains during the holiday. Third, he strictly followed the tips I provided for eating. Despite consuming a significant amount and feeling full, he still lost weight." Chen Chaogang explained that the hospital is conducting a study and recruited 60 volunteers before the Spring Festival, providing each with a personalized meal plan based on their individual situations. In recent days, several participants have come in for weigh-ins and found they have lost weight following the meal plan. However, one man, who has had a long-term habit of skipping breakfast, actually gained weight. Analysis of his situation suggests that frequently missing breakfast led to larger portions at lunch and dinner.

"I always emphasize to overweight individuals who come in for consultations that scientific weight loss should consist of three plus one. The first is strict control of oil; we need to carefully monitor the amount of oil used in cooking, allowing only one spoonful per person per meal (approximately 10 grams), with a maximum of three spoonfuls a day. It is also important to strictly control the oil content in processed foods—such as fried doughnuts, oil cakes, cream cakes, and bread, which all contain a lot of oil—as well as to appropriately limit the intake of meat, dairy, eggs, and other fatty foods. The second point is to increase vegetable intake. Currently, the vast majority of overweight and obese patients at the hospital do not consume enough vegetables. When eating, one should start with two types of oil-free vegetables, each weighing 200 grams: one leafy type such as spinach, leafy greens, or choy sum, and one non-leafy type like winter melon, pumpkin, or eggplant. Only after finishing the vegetables can one eat anything else. The third point is to have dinner as early as possible, ideally by six or six-thirty in the evening. Additionally, physical activity should be increased." He smiled and added that he always checks his phone before going to bed to see if he has walked enough to reach ten thousand steps.

Chen Chaogang has repeatedly made it clear to reporters: "Weight loss should be pursued in a healthy and comfortable living state, without affecting work or mood; otherwise, it’s hard to stick to it. You shouldn’t starve; you need to eat enough!" To sum it up, breakfast should not be skipped, lunch should be sufficiently hearty, and dinner should be eaten early. Some say that any food consumed after 7 PM counts as a "midnight snack," and Chen Chaogang believes there is some truth to this, suggesting that eating after 7 PM should be minimized. So, what about those who finish work late? He suggests they should try to have their meals earlier, or immediately consume some staple foods, dairy, and fruits after work. For dinner, they should focus on eating low-oil vegetables and soy products, and they can also choose to increase their activity time and amount after dinner.

It is wrong to lose weight by not eating carbohydrates.

Many celebrities say that carbohydrates are very high in energy and that they haven't eaten a grain of rice in many years. In response to this claim, Chen Chaogang pointed out, "What affects weight is the total energy intake, not carbohydrates. Fats are high in energy and mixed in various foods, making them the hardest to manage, so they require particular attention and control." On the contrary, he suggests that people trying to lose weight should eat a bowl of rice for both lunch and dinner. Those who are tall should consume 100 grams (measured uncooked) of rice, those of average height should have 75 grams, and shorter individuals should eat 50 grams.

In addition, a balanced diet is also very important. Fruits and vegetables are not only low in calories, but the dietary fiber they contain provides a feeling of fullness and helps to reduce fat intake. They are also rich in many essential nutrients, so it is important to ensure an adequate intake of these foods.

Additionally, Chen Chao just added that while intermittent fasting is beneficial for physical and mental health, it may trigger abnormal metabolism in patients with hypertension, diabetes, cardiovascular diseases, high uric acid, gout, and menstrual disorders. Therefore, intermittent fasting is not recommended for these individuals. If such a patient wishes to try it, they should first seek medical advice and consult with their doctor.

Finally, it's important to remember not to pursue rapid weight loss. Chen Chaogang pointed out that normal, scientific weight loss is about 2 to 4 kilograms per month. For example, a certain celebrity who recently gained popularity lost 50 kilograms in a year, which averages around 8 kilograms per month. While this might seem reasonable based on the numbers, losing such a large amount of weight each month should be done under medical supervision and should not be blindly imitated.

Content from: Guangdong Province Association for Science and Technology

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