Fruit-based diets and the misconceptions of "intermittent fasting": Deciphering the energy trap and disruption of circadian rhythms.

The 5-Fruit-a-Day Diet: I. How Much Energy Does Fruit Actually Contain? Fruit refers to edible, juicy plant fruits with a predominantly sweet and sour taste. There are many types of fruits, which can be divided into five categories based on their morphology and physiological characteristics: pome fruits, drupes, berries, citrus fruits, and melons. They are also classified by region, such as tropical and subtropical fruits. Many people believe that fruits are low in energy and rich in various vitamins and minerals, making them ideal for weight loss. However, different types of fruits have significantly different energy contents due to variations in water content and the content of energy-producing nutrients. Generally speaking, fruits with higher water content and lower protein, fat, and carbohydrate content are lower in energy, such as apples, pears, grapes, strawberries, and watermelons. Conversely, some fruits with lower water content and higher protein, fat, and carbohydrate content have relatively higher energy content, such as avocados, jujubes, jackfruit, coconuts, and durians. Furthermore, the energy content of fruit is also related to its weight. Although 100g of watermelon has relatively low energy, a medium-sized watermelon can contain several hundred kilocalories due to its considerable weight. While jujubes have a relatively high energy content per 100g, a single jujube only contains a few kilocalories. Secondly, can eating five fruits a day really help with weight loss? Currently, there is no scientific research showing that eating five fruits a day can lead to weight loss, nor has any authoritative organization or institution published related claims. Those spreading this information simply specify the number of fruits, without specifying the size, type, or method of consumption; a closer look reveals its deception. Ignoring the energy differences caused by fruit size and type, eating only five low-energy fruits daily, resulting in lower energy intake than daily expenditure, would indeed lead to weight loss. However, most fruits are extremely low in protein and fat, and relying solely on fruit cannot meet the body's normal nutritional needs, inevitably leading to health problems in the long run. Furthermore, once a normal diet is resumed, weight will quickly rebound. On the other hand, consuming five more fruits after a full meal actually increases energy intake, not only failing to achieve weight loss but also leading to weight gain. Even if fruits are freely combined with other foods without restrictions on how they are eaten, excessive fruit consumption is still detrimental. Most fruits contain 6%-28% sugar, primarily fructose, glucose, and sucrose. Fructose has a high sweetness, which stimulates appetite and leads to increased energy intake. Furthermore, excessive fructose intake can promote fat synthesis, thus exacerbating obesity. III. Using Fruit for Weight Loss: The health benefits of fruit have been proven. Many studies have shown that eating fruit can effectively alleviate obesity and obesity-related diseases such as diabetes and coronary heart disease. Possible reasons include: the dietary fiber in fruit provides a strong feeling of fullness; most fruits have low energy density, and replacing high-energy-density foods with them can reduce total daily energy intake; fruit provides essential micronutrients, alleviating obesity through various potential mechanisms; phytochemicals in fruit, such as resveratrol, caffeic acid, naringin, and proanthocyanidins, also have anti-obesity effects; and the abundant dietary fiber and polyphenols in fruit improve obesity by regulating gut microbiota. However, using fruit for weight loss requires proper methods. First, it's important to control fruit intake. The Chinese Dietary Guidelines recommend a daily fruit intake of 200-350g for healthy adults, roughly equivalent to one medium-sized apple to one medium-sized orange. Secondly, choose suitable fruit types, prioritizing low-energy and highly satiating fruits. Finally, choose appropriate ways to consume fruit. Fruit can be eaten as a snack, replacing some high-fat, high-energy foods between meals. Fruit can also be consumed before meals to raise blood sugar and increase satiety, thus reducing the amount of food consumed at main meals. Alternatively, fruit can replace staple foods at main meals, combined with other vegetables, meat, poultry, eggs, and dairy products. The "no food after noon" diet has resurfaced in the public eye, believed to be beneficial for health, and is considered a "winning formula" for weight loss. However, does "no food after noon" really work for weight loss? Is it a scientific and healthy method? I. Where does "no food after noon" come from? Many people now believe that the concept originated from Traditional Chinese Medicine. However, it actually originated from Buddhism. Several Buddhist texts, such as the *Sariputra's Questions Sutra* and the *Treatise on Breaking Through Appearances*, explain its origins. The Buddhist precept of not eating after noon should be accurately understood as "not eating at inappropriate times," meaning not eating outside of permitted mealtimes. Further analysis suggests that not eating after noon refers to abstaining from food between 12 noon and dawn the following day. Although the ancient Chinese medicine master Yu Chang mentioned "Buddhism's prohibition against eating after noon" in his medical records *Yuyi Cao*, this was merely to illustrate the importance of mealtimes for health maintenance. Secondly, "not eating after noon" is like a mirage. Mr. Zhao Puchu, former president of the Buddhist Association of China, once explained the significance of the Buddhist precept of not eating after noon in his *Questions and Answers on Buddhist Common Knowledge*: "Monks' meals are provided by laypeople, and they only receive their alms once a day, eating once at midday, which reduces the burden on laypeople. In addition, not eating after noon is helpful for spiritual practice." Nevertheless, Buddhism also has its flexibility in implementing the precept of not eating after noon; for example, Buddhists are allowed to consume medicinal foods. The so-called "medicinal food" refers to dinner. It's called "medicinal food" to remind monks not to crave food; the temple dinner should only be considered a remedy for hunger. This is because Chinese monks, unlike their Indian counterparts, must participate in labor and therefore need to consume energy in the afternoon to meet their physical needs. Furthermore, the "tea soup" and "tea substitutes" consumed by monks in temples contain carbohydrate-rich ingredients such as dates, barley, and kudzu root. Consuming these in the afternoon also replenishes the body's energy, effectively serving as a form of dinner. This aligns to some extent with the modern nutritional concept of "eat a good breakfast, a full lunch, and a light dinner." Therefore, the absolute "no food after noon" is like a mirage-it seems to exist, but may not be practically applicable. III. The "no food after noon" weight loss method: While the pace of life in ancient society was slow, with sufficient material resources, the three-meal-a-day system was widely accepted and gradually replaced the two-meal-a-day system as the mainstream. This reflects the scientific basis of the three-meal-a-day system. Compared to ancient people, modern society has significantly delayed sleep at night, and the energy expenditure for physical and mental activities in the afternoon and evening is much greater. Therefore, appropriate snacks and dinners are even more important. Using "intermittent fasting" to extend the fasting period may have a weight-loss effect. In a short-term state of hunger, the body utilizes stored energy substances to ensure the energy supply to vital organs. First, it uses glucose from the breakdown of glycogen, and then uses glucose converted from amino acids and glycerol through gluconeogenesis. When the body's protein intake is insufficient, the proteins in organ tissues, such as skeletal muscle, will be broken down to produce amino acids. The consumption of muscle tissue leads to a series of symptoms such as decreased exercise endurance. However, the goal of weight loss is to reduce excess body fat and increase muscle mass to achieve a better state of health. "Intermittent fasting" leads to weight loss while also losing muscle, which contradicts the concept of weight loss for health. Studies have shown that practices like "intermittent fasting," which reduce meal frequency, may not be significantly effective in reducing weight or increasing energy expenditure, and may even have many negative effects on the body. Reducing the frequency of daily meals and altering eating rhythms can disrupt leptin release, glucose and energy metabolism, and insulin sensitivity, potentially leading to obesity and metabolic syndrome. Decreased meal frequency can affect satiety, increasing binge eating and potentially contributing to gastrointestinal issues like gastritis. Therefore, blindly following the "no food after noon" diet for weight loss is not advisable. As the saying goes, "Listen carefully to the meaning, dig up the roots of the tree," meaning we shouldn't just take things literally; we must get to the bottom of things and think carefully before acting to avoid pitfalls. Respecting the body's biological rhythms, controlling energy intake, and engaging in moderate exercise are the right ways to lose weight.