Calculation of daily calorie requirements for the human body and methods for calculating food calories

Every day, we ingest a certain amount of fat, protein, carbohydrates, fiber, minerals, and various trace elements from our food. The amount of these substances we consume is closely related to obesity. Therefore, to achieve weight loss through diet, we must first understand how many calories a normal human body needs to burn each day.

The total calories consumed by the human body each day are roughly distributed across three areas: basal metabolism, metabolic activity, and the calories consumed in digesting food. Basal metabolism and metabolic activity are the primary sources, as the calories consumed from food itself constitute only a small portion.

So, what is basal metabolism?

It refers to the amount of heat energy required to maintain life when the body is in a quiet, alert, relaxed, and fasting state. Specifically, it refers to the amount of heat energy required for the human body to maintain body temperature, pulse, respiration, and muscle expansion and contraction in a quiet and relaxed state.

Basal metabolic rate (BMR) varies depending on factors such as age, sex, height, and season. Generally, men have a higher BMR than women, and a higher BMR in winter than in summer. Before age 25, the amount of calories required for BMR gradually increases with age; after age 25, BMR begins to decline, slightly later for men. During this period, if calorie intake does not decrease, but metabolism continues to decline, the body no longer needs as many calories, resulting in more calorie intake than expenditure. This leads to excess calories being converted into fat, causing weight gain.

The energy consumed by labor refers to the amount of heat a person expends in various social activities, constituting a major portion of the body's total energy requirements. Some data show that it is related to the intensity of labor, the duration of labor, and the level of skill in the work. Those engaged in light physical labor require an additional 150 kcal/hour, while those engaged in heavy physical labor require an additional 400 kcal/hour.

In addition to the above, food also consumes energy through its own dynamic processes. Because the body's energy metabolism increases after ingesting food, the food itself also consumes a portion of its energy. Various foods have specific dynamic processes. Protein has the strongest dynamic process, accounting for 25-35% of its own energy production. Therefore, when calculating one's calorie expenditure, for those who regularly consume a mixed diet, 4-5% of the energy required for physical exertion should be added, while for those who consume a high amount of protein, 8-11% should be added.

Generally, an adult male needs 2,600 to 4,200 kcal per day. Women need about 5% less than men (except for pregnant women). An average man over 65 years old needs 2,400 kcal per day, and an average woman needs 2,100 kcal per day.

How do you calculate the calorie content of food?

We obtain energy from our daily diet to sustain life, and most foods contain a certain amount of energy. Food generally contains water, protein, fat, carbohydrates, fiber, alcohol, vitamins, and minerals. Energy primarily comes from the oxidation of proteins, carbohydrates, and fats. The energy ingested by the human body is the sum of the energy provided by usable carbohydrates, fats, and proteins from food. Below is a brief introduction to these substances.

carbohydrate

Much of the energy in our bodies comes from carbohydrates. Carbohydrates mainly include starch, sugar, and fiber. Starch can be obtained from rice, flour, potatoes, and sweet potatoes. We need about 100 grams of carbohydrates per day to maintain our weight.

protein

It is the foundation of all life, providing the necessary material basis-amino acids-for the production of new proteins in the body. Our bodies require more than 20 different amino acids. Some foods may contain proteins with low levels of one or more of these amino acids; these foods are collectively referred to as low-protein foods. Consuming only low-protein foods is very detrimental to health.

Choosing a certain amount of low-protein foods while supplementing them with an appropriate amount of high-protein foods is more beneficial to health. High-protein foods mainly refer to meat, fish, eggs, and milk. How much high-protein and how much low-protein food should a normal person consume daily for the optimal dietary balance? This requires further research and exploration by scientists. However, it can be clearly stated that consuming only high-protein foods or only low-protein foods is not a scientifically sound choice. Even obese individuals using dietary therapy to lose weight should maintain a certain level of protein intake.

Fat

It is a major source of energy for the human body. The human brain is mainly composed of fat, and many hormones in the body are also primarily composed of fat. A woman's curves and smooth skin are also due to the presence of fat. Therefore, fat can influence both appearance and body shape, all depending on our ability to control the fat in our bodies.

Fats are generally classified into saturated fats and unsaturated fats.

Animal fats can solidify at high temperatures, hence the name saturated fats, which can be converted into cholesterol. Unsaturated fats, such as those extracted from corn and soybeans, not only cannot be converted into cholesterol, but can also reduce the accumulation of cholesterol in the blood.

Dietary weight loss methods place great importance on controlling fat intake, especially animal fat, which can be considered the key to weight loss to a certain extent.

So, how is the calorie content of food calculated?

The average amount of energy released when 1 gram of protein, fat, and usable carbohydrates is burned is 5.65 kcal, 9.45 kcal, and 4.1 kcal, respectively. Under normal circumstances, the digestibility and absorption rate of fat is 95%. Therefore, the effective energy content of fat is: 9.45 × 95% = 9.0 kcal/gram.

The digestibility and absorption rate of available carbohydrates is 98%, therefore the effective energy from available carbohydrates is: 4.1 × 98% = 4.0 kcal/g.

The digestibility and absorption rate of protein is 92%, but each gram of protein cannot be completely oxidized in the body, and the portion excreted still contains 1.3 kcal of energy. Therefore, the effective energy of protein is: (5.65 - 1.3) × 92% = 4.0 kcal/gram.

In this way, we can calculate the calorie content of food. For example, beef contains 49% water, 15% protein, 36% fat, and no carbohydrates. Therefore, 100 grams of beef contains the following calories:

Protein: 15g × 4kcal/g = 60kcal

Fat: 36 grams × 9 kcal/gram = 324 kcal

Water does not produce heat, so 100 grams of beef contains 384 kilocalories.

Thus, we know that the general formula for calculating the calorie content of food is: A×4 + B×9 + C×4 = Calorie content of food. Where A, B, and C represent 100 grams of carbohydrates, fat, and protein, respectively.

Knowing this formula, you can calculate the calorie content of food, combine foods according to your needs, and make scientific and reasonable dietary arrangements.