Sugar, fat and protein are the three major energy substances in human body. They are not only raw materials for human cells, but also provide energy for cell life activities. They have different functions and characteristics.
Sugar is the main energy substance in the human body, and more than 70% of the energy needed for life activities in the human body comes from the decomposition of sugar. Sugar mainly comes from sweet potatoes, potatoes, sugar and cereals.
Fat can also provide energy for the human body, but it is usually stored in the human body as a spare energy substance. Fat mainly comes from meat, oil and other foods.
Protein, fat and carbohydrate not only have unique physiological functions, but also are energy-producing nutrients, which cooperate and restrict each other in energy metabolism. For example, fat must contain carbohydrates in order not to produce too many ketone bodies, leading to acidosis.
Carbohydrate and fat can be transformed and replaced in the body, but protein cannot be replaced by fat or carbohydrate. But the abundant supply of fat and carbohydrates will prevent protein from being an energy source.
When energy intake exceeds consumption, no matter whether the excess energy comes from fat, protein or carbohydrates, it will be converted into fat and stored in the body, which will lead to obesity.
Among protein, fat and carbohydrate, fat produces the largest unit energy, with 9 kilocalories per gram of fat. Protein and carbohydrates are 4 kilocalories per gram. Fat and carbohydrate bear the main task of energy supply. This is because although protein can also be used for energy supply, it should be protected as much as possible, instead of being consumed as energy, because it constitutes an important duty of the body and its bioactive substances (such as various enzymes and antibodies) are limited in the body.
Therefore, the three thermogenic nutrients should have an appropriate proportion. According to the eating habits and characteristics of China people, the proportion of total energy in protein should be 15% ~ 20%.
The proportion of fat in total energy should be 25% ~ 30%.
The proportion of carbohydrates in total energy should be 55% ~ 60%.
Of the seven essential elements of human body, only three are energetic, namely carbohydrate, fat and protein. They are called: the most active carbohydrate, the fat with great function and the protein who is afraid of burning. In the normal consumption process of human body, carbohydrates are consumed first, followed by fat. Both must be catalyzed by enzymes and coenzymes. Without enzymes, protein will burn.