The Art of Energy Balance: A Detailed Explanation of Intake, Consumption, and Basal Metabolism

Daily calorie intake < Daily calorie expenditure

2.2.3 The Way to Balance Energy Intake and Consumption

A balance of energy intake and expenditure is essential for maintaining good health. Since energy must be conserved, the energy-producing nutrients we ingest must equal the energy we expend.

In Chapter 1, we learned about the three main pathways for energy production in the human body. The human body has three major energy-producing nutrients: carbohydrates, fats, and proteins, which produce 4kcal, 9kcal, and 4kcal of heat per gram, respectively.

The energy consumed by the human body is used for the following purposes: basal metabolism, physical activity, the thermic effect of food, growth and development, and other factors that affect energy consumption.

Basal metabolic rate (BMR) refers to the minimum energy required by the human body to maintain life. It is the metabolic state achieved when the body is completely at rest and relaxed, without physical or mental exertion, gastrointestinal activity, and the person is awake and resting comfortably at a room temperature of 20-25°C. Many factors influence BMR, including body type, sex, age, physiological state, season, and intensity of physical activity. Generally, BMR is higher in men than women, higher in children and adolescents than adults, and higher in cold climates than in hot climates.

Physical activity is a major factor in human energy consumption. While people with similar physiological conditions have similar basal metabolic rates, their levels of physical activity vary greatly. Even slight activity can increase the metabolic rate, and oxygen consumption increases significantly during exercise or labor. This is because muscles need to consume energy during physical activity, which comes from the oxidation of nutrients, inevitably leading to increased oxygen consumption. The increase in oxygen consumption is directly proportional to the intensity of muscle activity. Oxygen consumption can reach 10 to 20 times the resting level. Typically, the energy consumed by various physical activities accounts for 15% to 30% of the body's total energy expenditure.

The thermic effect of food refers to the increased energy expenditure resulting from food consumption. This is because the processes of digestion, transport, metabolism, and storage require energy. The thermic effect varies among different nutrients, with protein having the strongest effect, followed by carbohydrates, and fat having the weakest. Generally, the thermic effect of a mixed diet accounts for approximately 10% of the total daily energy expenditure.

Other factors affecting growth and development, and their impact on energy expenditure, are as follows. Children and adolescents require energy to build new tissues; approximately 20 kJ of energy is needed for every 1 gram of new tissue. Similarly, the growth and development of the fetus and the development of the mother's own organs and reproductive system also require energy. Energy intake must be proportionate to the rate of growth; otherwise, growth will slow down or even stop.

To maintain a balance between income and expenditure, i.e., daily fat accumulation = 0, the following equation must be satisfied:

Daily calorie intake = Daily calorie expenditure

2.3 What foods can lead to obesity?

2.3.1 The Sin of Food ------ High sugar and high fat equal high calories

A long-term diet high in oil and sugar, and low in fiber, such as soda, cola, canned drinks, hamburgers, and French fries, can create a breeding ground for chronic diseases later in life. For example, frequently eating fried foods not only makes it difficult to control waist circumference but also raises cholesterol levels and damages the liver. Excessive consumption of fried foods for a month can cause liver damage similar to hepatitis. Besides Western fast food, Chinese fast food (boxed meals) is also high in calories, and eating too much of it is not good for your health.