Meal frequency and weight loss efficiency: Analyzing the health risks of "skipping a meal" and the limitations of coffee as a supplementary weight loss aid.

The "skip a meal" diet is probably the most common weight loss method that comes to mind for ordinary people. Nowadays, many young people stay up late, not resting until the early hours of the morning, skipping breakfast, and only eating lunch and dinner. Therefore, the "skip a meal" diet is prevalent. A 2019 study on the dietary behavior of Chinese residents showed that the proportions of Chinese residents who skip breakfast, lunch, and dinner were 4.4%, 1.4%, and 0.2%, respectively. But does the "skip a meal" diet actually help with weight loss? The theory behind the "skip a meal" diet is to control energy intake and achieve weight loss by reducing the frequency of meals. However, the effectiveness of this method may only exist in theory. Although some studies indicate that skipping breakfast for a short period can reduce total daily energy intake to some extent, and the decrease in total energy intake may be greater than the decrease in energy expenditure (negative energy balance), several long-term observational studies suggest that skipping breakfast has no significant effect on weight, and some studies even indicate that skipping breakfast may lead to weight gain. Existing research lacks high-quality intervention studies to support the role of prolonged breakfast skipping in maintaining negative energy balance, or to demonstrate that prolonged breakfast skipping leads to significant weight loss. Other studies indicate that eating three or more meals a day has little impact on food intake, while two or fewer meals a day negatively affect appetite control. Skipping a meal is harmful. Skipping a meal, or skipping breakfast, can have numerous negative health effects. As early as the 1960s, research indicated a link between daily meal frequency and overweight, high cholesterol, and impaired glucose tolerance. Recent meta-analyses also suggest that skipping breakfast is a risk factor for type 2 diabetes. Skipping a meal prolongs the interval between the remaining two meals, putting the body in a short-term state of hunger. In this state, the body first uses glycogen to break down into glucose for energy, and then uses glucose converted from amino acids and glycerol through gluconeogenesis. When protein intake is insufficient, the protein in organs and tissues will be broken down to produce amino acids, leading to muscle wastage. Muscle loss not only slows down the body's metabolic rate, making it easier for fat to accumulate, but also leads to loose skin, decreased immunity, weakened muscle endurance and core strength, and increased fatigue. International studies have confirmed that subjects who consumed carbohydrates in the morning performed better in exercise compared to those who fasted. In conclusion, the "skip a meal" diet's weight loss effect is unknown, but its health risks are relatively clear. A combination of diet and exercise is a more effective way to achieve long-term weight loss goals. Regular meals and maintaining a reasonable eating frequency not only help maintain good physical condition but also help prevent the development of long-term diabetes and cardiovascular diseases. The coffee diet, as the name suggests, involves drinking black coffee daily, utilizing its low-calorie, water-reducing, and bowel-promoting properties to achieve weight loss. According to current research, chlorogenic acid, caffeine, and dietary fiber in coffee may be the substances that contribute to its weight-loss effects. Chlorogenic acid, as a polyphenolic phytochemical, has various effects such as anti-inflammation, diabetes prevention, and promoting gastrointestinal motility and gastric juice secretion; dietary fiber promotes gastrointestinal motility and gastric emptying. Caffeine, present in approximately 100mg per cup of coffee (240ml), is considered a key substance contributing to coffee's weight-loss effects. Studies have shown that caffeine can influence the body's energy balance, increasing metabolic rate, accelerating energy expenditure, promoting lipid oxidation and thermogenesis, thereby contributing to weight control to some extent. However, this effect is relatively limited: in one study, a caffeine intake of 300mg/day only resulted in an additional 79kcal of energy expenditure. According to the principles of weight loss, losing 1kg requires an average of 7200kcal of energy expenditure. Based on this comparison, it's clear that achieving a daily weight loss of 0.5kg by simply drinking about 3 cups of coffee is unrealistic. Furthermore, the weight-control effect of caffeine was observed in subjects with relatively low caffeine intake; whether long-term consumption has this effect is currently unsupported by data. High caffeine intake can have several effects on the body: large doses can cause gastrointestinal symptoms such as nausea, vomiting, and general discomfort; a European study found a possible link between coffee consumption and chronic atrophic gastritis; and excessive caffeine intake can also raise blood pressure, increasing the risk of hypertension. To minimize side effects, healthy adults should limit their daily caffeine intake to no more than 400mg, while pregnant women should limit it to no more than 300mg/day. It has been reported that some weight-loss coffees illegally add sibutramine, an appetite suppressant, to achieve weight loss. This substance can induce heart disease and stroke, posing significant health risks. While coffee's role in weight management has been proven, relying solely on coffee for weight loss is unlikely to be effective. Coffee can be used as a supplement to accelerate metabolism, but the core of weight loss remains controlling energy intake and increasing energy expenditure. The correct way to use coffee is to choose high-caffeine black coffee, avoid adding sugar or other flavorings to prevent increased energy intake, and engage in physical activity after drinking it to increase energy expenditure.