The interrelationships and consumption order of energy substances in the human body

The three major energy substances in the human body and their relationship

1.2.1 Without energy, there is no life

Just as a car needs fuel to run, all human life activities require energy. It can be said that without energy, there is no life! Solar energy enters plants through photosynthesis and then enters the human body through the food chain of "plant → animal → human." Of course, energy itself is not a nutrient; it is released from the breakdown and metabolism of proteins, fats, and carbohydrates in food within the body.

Generally speaking, the energy supply process is as follows: the human body eats → food releases energy → energy maintains body temperature and enables normal physiological activities. Cell growth, reproduction, and self-renewal, the transport and metabolism of nutrients, and the elimination of waste all require energy. Even during sleep, the body's respiratory, digestive, endocrine, and circulatory systems consume energy.

1.2.2 The Interrelationships of the Three Major Energy Substances

The three major nutrients-protein, fat, and carbohydrates-not only have their unique physiological functions but are also energy-producing nutrients, working in tandem and regulating each other in energy metabolism. For example, fat requires the presence of carbohydrates to prevent the production of excessive ketone bodies and subsequent acidosis. Carbohydrates and fats can be interconverted and substituted for each other in the body, while protein cannot be replaced by either fat or carbohydrates. However, an adequate supply of fat and carbohydrates can prevent protein from being used as an energy source. When energy intake exceeds expenditure, regardless of whether the excess energy comes from fat, protein, or carbohydrates, it will be converted into fat and stored in the body, leading to obesity.

Among the three macronutrients (protein, fat, and carbohydrates), fat has the highest energy production per unit, producing 9 kcal per gram; protein and carbohydrates both produce 4 kcal/g. Fat and carbohydrates thus play a primary role in providing energy. This is because, although protein can also be used for energy, its crucial role in building the body and forming vital substances (such as various enzymes and antibodies), coupled with its limited quantity in the body, necessitates its protection rather than being consumed as an energy source.

Therefore, the three major energy-producing nutrients should be in an appropriate ratio. According to the dietary habits and characteristics of Chinese people, protein should account for 15% to 20% of total energy, fat should account for 25% to 30% of total energy, and carbohydrates should account for 55% to 60% of total energy.

1.2.3 The "Obstacles" to Weight Loss from the Perspective of Interrelationships

In physics, we often say that the most efficient component will provide energy first. This means that the most efficient component doesn't necessarily contain the most energy, but the component that provides energy the fastest will provide it first; this is called kinetic efficiency. For example, if a car contains gasoline, diesel, and alcohol-all three of which can provide energy-the alcohol will provide energy first, followed by the gasoline, and finally the diesel. In fact, diesel has the highest calorific value, but it has the lowest kinetic efficiency.

The consumption of carbohydrates, fats, and proteins follows the same principle; their utilization efficiency differs, so the order in which they are consumed by the body also differs. Simply put, it's like the money in our pockets, our savings, and our property. If we go to buy groceries, what asset do we use first? We certainly wouldn't sell our house to buy vegetables! We'd use our money first. Therefore, regardless of the type of exercise you do, the body will first consume the energy derived from carbohydrates.

So when do we use our savings (fat)? When our cash (carbohydrates) runs out, we have to withdraw from our savings account, and that's when fat starts to be used. So when do we have to sell or pawn our house (protein)? Generally, we only draw on our fixed assets (protein) when our savings (fat) are nearly depleted.

However, according to the principle of "not providing too little protein," insufficient protein intake can affect the speed of growth and development, reduce biochemical reactions, decrease disease resistance, lead to malnutrition, and may even cause growth retardation, intellectual disability, and other consequences. Therefore, the body should not be allowed to easily break down protein to supply energy. If the body breaks down too much essential protein in order to obtain energy, irreversible pathological infections will occur, causing irreparable damage to the body.

From the analysis of the relationship among these three factors, we can understand that: dieting initially shows noticeable results because the body primarily consumes carbohydrates rather than fat; however, once the diet is relaxed even slightly, weight rebounds. Excessive dieting ultimately leads to the consumption of protein, resulting in drastic weight loss, anorexia, and other unhealthy conditions. Nutritionists believe that deliberate dieting puts the body in a state of malnutrition, and prolonged malnutrition inevitably causes organs to experience chronic starvation, leading to organ dysfunction.

The effects of excessive dieting on human organs are as follows:

Liver: Serum protein synthesis is reduced, and circulating protein levels decrease.

Heart: Reduced blood output and decreased myocardial contractility.

Lungs: Weak and atrophied respiratory muscles, reduced vital capacity and tidal volume, and impaired mucociliary clearance function.

Stomach: Digestive function declines because stomach acid is still secreted, but there is no food for the stomach to digest. The stomach acid will then begin to irritate itself, leading to diseases such as chronic gastritis and gastric ulcers.

Kidneys: Decreased function can cause general weakness, lethargy, and decreased libido. In a few cases, it can also cause varying degrees of edema in both lower limbs.

Brain: Due to dieting, the brain is also in a state of chronic malnutrition. Its nerve cells will be relatively ischemic and hypoxic, thus memory will decline and thinking ability will decrease.

In addition, dieting can cause nutritional diseases, such as protein-calorie malnutrition. Mild cases result in weight loss, dry skin, thinning hair, and generalized edema, while severe cases lead to a decline in overall physical quality. These are the drawbacks of dieting for weight loss.

Analyzing the relationship among these three factors reveals that carbohydrates are a major obstacle to weight loss. To quickly burn fat, you need to exercise at an intensity of 75% of your maximum minute inhalation for at least 45 minutes. This explains why some women walk for two hours a day for six months without losing any belly fat; they simply consume the sugar and convert it into fat. However, the existing fat doesn't have time to be broken down, resulting in the biggest change being in their calves, which actually become thicker.

Appropriately reducing carbohydrate intake is beneficial: it suppresses the rise in blood sugar levels and makes stored fat easier to use as energy. However, excessively reducing carbohydrate intake is also bad, as it can lead to insufficient brain nutrition and difficulty concentrating; the breakdown of sugar stored in the liver will impair liver function; the breakdown of protein in the body will make the body prone to fatigue; and it will disrupt the body's pH balance, making the blood more acidic and causing drowsiness.

Drastically reducing carbohydrate intake can have significant negative effects. A low-carbohydrate diet aims to limit daily intake to one-third to one-half of your usual amount.

The key to a low-carbohydrate diet is controlling your sugar intake from high-sugar foods like rice and wheat-based bread. This is why you can't eat rice, steamed buns, or noodles indiscriminately. Even if you avoid all oil after eating these foods, you still won't lose weight. Why? Because these are excellent sources of carbohydrates! Sugar intake should be controlled especially at night, as physical and mental activity levels are lower, making it harder to metabolize sugar. Furthermore, consuming carbohydrates alongside vitamins B1 and B2 ensures that sugar is efficiently converted into energy. Foods rich in vitamin B1, such as leeks, garlic, and onions, are highly effective for this purpose.

Remember: Low-sugar diets can have the opposite effect if taken too drastically.