Caloric knowledge

1. Who can tell me something about calories?

Calories are calories.

Calories (abbreviated as "cal", abbreviated as "cal") It is defined as the amount of heat required to raise 1 gram of water by 1 degree Celsius at 1 atmosphere of pressure.

The "15-degree calorie" used in nutrition: the amount of heat required to raise 1 gram of water from 14.5 degrees Celsius to 15.5 degrees Celsius at 1 atmosphere of pressure is approximately equal to 4.1855 joules.

Since the unit of "calorie" is still too small compared to our daily intake of calories, nutrition science now generally uses another unit "kilocalories" (kcal or C, also known as "kcal") that evolved from "calories". Called "daka"). 1 kcal is equal to 1000 calories, approximately 4186 joules. The calories of fat are about 9 kilocalories per gram; the calories of sugar and protein are only 4 kilocalories per gram.

2. How many calories does the human body absorb every day?

To maintain the current weight, a person must eat 30 to 35 calories per kilogram of body weight every day.

A 50-kg person will maintain his current weight if he eats 1,500 to 2,000 calories a day. If you eat an extra 250 calories a day for a month, you will gain one kilogram.

On the contrary, if you eat less than 250 calories a day for a month, you can lose one kilogram; if you eat less than 1,000 calories a day for a week, you can also lose one kilogram. In other words, every 7,000 calories can be exchanged for one kilogram of meat.

Physiologically, the human body requires at least one thousand calories of food calories per day in order to operate safely and effectively. Otherwise, the protein in the heart muscle and vascular smooth muscle will gradually lose and cause cardiovascular disease, and in severe cases, death. There are often reports abroad of deaths due to daily total calorie intake of less than 500 calories. In addition, if the food calories of less than 1,000 calories per day are maintained for a long time, human cells will turn into cancer cells due to long-term nutritional deficiencies, which will lead to the unfortunate outcome of cancer decades later. This is something that most people have never thought of.

Long-term malnutrition is one of the main causes of cancer. Because some people often use unhealthy weight loss products or diet frequently, their metabolic levels may be lower than ordinary people, which means they can maintain their current weight without taking in so many calories, so please do not use unhealthy weight loss methods casually. .

3. How many calories should an adult consume every day?

According to the book "Calories and Protein Intake" published by the World Health Organization, a healthy adult woman needs to consume 1,800 calories a day. ~1900 calories, men need 1980~2340 calories.

Among them, the protein intake should be 10% to 15% of the human body’s daily caloric requirements; the carbohydrate intake should be no less than 55% of the human body’s daily caloric requirements; and the fat intake should be No more than 30% of daily caloric requirements. In addition, the daily intake of salt should not exceed 6 grams, and the daily intake of dietary fiber should not be less than 16 grams.

Taking a healthy adult woman as an example, the average calorie content of each meal should be 600 to 650 calories, which is equivalent to 10 to 12 black sesame glutinous rice balls, 12 to 15 dumplings, or 4 Spring pancakes rolled with bean sprouts and shredded pork in sauce. And if you are eating hot pot, it is equivalent to 50 grams of mutton, 50 grams of fat beef, 150 grams of various green vegetables, 50 grams of tofu, plus a sesame seed cake and a bowl of thick mutton soup.

Men should consume more calories per meal than women, about 680 to 800 calories. When converted into food, it is about a quarter more than women, that is, they should consume 12 to 15 calories per meal. Black sesame glutinous rice balls, 15 to 20 dumplings, 5 to 6 spring pancakes rolled with bean sprouts and shredded pork, or 60 grams of mutton, 60 grams of beef, 180 grams of various vegetables, 60 grams of tofu, plus two sesame seed cakes and two Bowl of mutton soup. The following 10 methods are considered by experts to be the best ways to lose weight.

Based on an average daily intake of 2,000 calories. 1. Reduce caloric intake Nutritionists believe that no matter what you control - protein, carbohydrates or fat, what ultimately reduces is caloric intake.

If a person consumes 800 fewer calories a day, he can lose 10 pounds in six weeks; if he consumes 500 fewer calories a day, he can lose 10 pounds in two and a half months. But be careful not to lose weight too quickly, otherwise it will be very dangerous.

It should be noted that each person must consume at least 1,200 kcal of calories per day. If too little calories are supplied to the body, muscle will be lost. Muscles are the key for the human body to consume calories and promote metabolism.

2. Eat less fatty foods: Experts point out that every 1 gram of fat contains 9 kcal. Carbohydrates and proteins contain much lower calories per gram than fat, around 4 kcal.

Therefore, if you want to lose weight, you don’t have to eat less. You can replace the fat-containing foods (such as butter) you eat every day with fresh vegetables, fruits, and cereals. Experts believe that if you only eat 20-40 grams of fat can reduce weight by 10 pounds in 2 months. However, not everyone can lose weight if they eat less fat. If they eat too much carbohydrates, they will also gain weight.

3. . Reduce food intake: If you want to lose weight, you don't have to give up your favorite foods. The important thing is to control it. If you prefer a certain food and eat a large amount, you should pay attention to reducing the portion each time.

Instead of consuming 200 grams of meat 4 times a week, eat 100 grams each time. In this way, you can consume 1,200 fewer calories and lose 1 pound of weight in about 7 and a half months. It is recommended that dieters put a scale in the kitchen and post a reminder to remind themselves of the weight of food.

4. Eat more liquid food: Usually, it is very convenient to prepare liquid food. If you only consume liquid food or drinks, you can lose 10 pounds in 8 months.

The liquid diet should be varied to avoid nutritional deficiencies. You can even eat two meals a day under the guidance of a doctor. >

This can help you lose 10 pounds in 5 weeks, but make sure the liquid food you choose can provide the nutrients and protein your body needs, and ensure three meals a day.

5. Lose weight: Walk 5 kilometers once a day, 5 days a week, within 45 minutes each time. You can lose 10 pounds in 6 months.

If you walk 5 kilometers, you will lose weight faster.

In fact, time is squeezed out: use this method to lose weight. It may increase appetite.

Therefore, before or after walking, you can eat some low-fat foods or fresh fruits and drink more water to replenish the body water lost due to sweating. 6. Regular exercise: Every day. Regular exercise 3-5 times a week is a good way to reduce body fat, lose weight, increase muscle, and increase energy.

Running, 5 times a week, 45 minutes each time, 170 meters per minute. At the same speed, you can lose 10 pounds in 3 months; if you dance 6 times a week for 1 hour each time, you can lose 10 pounds in 4 months; if you swim 4 hours a week, you can lose 10 pounds in 4 months. Cycling, 4 times a week, 1 hour each time, at a speed of 15 kilometers per hour, can reduce 10 pounds in 5 months. If you have not done regular exercise before, do less at the beginning to prevent it. Harm the body.

Excessive exercise will increase food intake, which will not achieve the purpose of weight loss. 7. Strength training can strengthen muscles and increase metabolism. The faster. 45 minutes of weight training three times a week can help you lose 10 pounds in 10 months.

To avoid injury, you should ask a coach to help you choose the appropriate weight and develop an appropriate exercise plan. Stretch before and after exercise to maintain body flexibility, and the weight and frequency of weightlifting can be gradually increased.

8. Reduce calorie intake and combine it with walking: Substituting soda water for Coca-Cola can reduce the daily intake of 150 kcal. If you add 5 kilometers of 45-minute walks 5 times a week, you can lose 10 pounds in 3 months.

If you reduce the calories even more and still keep walking as mentioned above, you can lose 10 pounds in 7 weeks. 9. Combining fat intake with weight lifting: This method can consume excess fat in the body, maintain a good body shape, grow muscles, speed up metabolism, and promote cardiovascular health.

Eat 20 grams less fat every day and lift weights for 20 minutes, three times a week, and you can lose 10 pounds in three and a half months.

10. The best choice: Based on the above nine methods, formulate a step-by-step plan that can be implemented. The most ideal combination plan is to control fat intake, strengthen exercise and strength training.

As long as you have confidence and persevere, you will be able to lose weight, build muscle, and promote cardiovascular health and body metabolism. Reduce your calorie intake by 100 kcal every day, walk 3 kilometers three times a week for 30 minutes each time, and do weight lifting twice a week for 40 minutes each time.

With this combination, you can lose 10 pounds in 5 months. Let’s combine the three methods at the beginning.

4. What are the three basic ways of heat transfer?

(1) Thermal conduction, also known as thermal conduction. Thermal conduction refers to the dependence of molecules when there is no phase displacement between parts of an object or when different objects are in direct contact. The heat transfer phenomenon caused by the thermal movement of microscopic particles such as atoms and free electrons. Thermal conductivity pill, also known as thermal conductivity, refers to the amount of heat conduction per unit time per unit area of ??an object with unit thickness when there is a unit temperature difference.

(2) Thermal convection The phenomenon of transferring heat from one place to another relying on the movement of fluid is called thermal convection. Common heat transfer situations in engineering (such as shell and tube heat exchangers, tube bundles of steam boilers, condensers of refrigerators, etc.) are often not simple heat convection, but a heat exchange process when the fluid is in direct contact with the solid wall. At this time There is both heat convection and heat conduction, which is no longer the basic heat transfer method. It is called convection heat transfer (also called heat release).

The convection heat transfer surface heat transfer coefficient (sometimes referred to as the convection heat transfer coefficient) refers to the heat that can be transferred per unit area in unit time when the temperature difference between the fluid and the wall is unit, expressed determines the strength of the convective heat transfer process. (3) Thermal radiation The transfer of heat by emitting visible and invisible rays (electromagnetic waves) from the surface of an object is called thermal radiation, also known as radiation heat transfer.

Thermal radiation heat transfer process does not require direct contact between cold and hot objects to transfer heat like thermal conduction or thermal convection. (4) Heat transfer process The combination of the three basic heat transfer modes of heat conduction, heat convection and heat radiation forms a heat transfer process caused by temperature differences.

Ways to enhance and weaken heat transfer. The so-called enhancement of heat transfer is to increase the amount of heat transfer per unit heat transfer area of ??the heat exchange equipment, that is, to increase the heat transfer coefficient and reduce the thermal resistance of heat transfer. Impairing heat transfer refers to reducing the heat transfer coefficient and increasing the thermal resistance of heat transfer.

(1) Heat transfer coefficient and heat transfer resistance In engineering, we often encounter the process in which heat is transferred from the high-temperature fluid on one side of the solid wall to the low-temperature fluid on the other side through the solid wall, which is called the heat transfer process. . As shown in Figure 1M411042, it is assumed that the heat transfer process is in a steady state and the heat flow direction is perpendicular to the wall surface.

The basic calculation formula of heat flow in heat transfer: Q=k(tl-t2)A. According to 6-J, the heat transfer coefficient k: that is, the amount of cold and hot heat per unit time and unit wall area. The amount of heat that can be transferred per unit temperature difference between fluids. The A value can reflect the strength of the heat transfer process.

The thermal resistance of the heat transfer process is the sum of the heat transfer resistance of the cold and hot fluids and the heat conduction resistance of the wall, and has a reciprocal relationship with the heat transfer coefficient. For heat exchangers, the larger the value of heat transfer coefficient K, the smaller the value of heat transfer resistance R, and the better the heat transfer; for the insulation of thermal pipes, the smaller the value of heat transfer coefficient K, the larger the value of heat transfer resistance R. , the better the thermal insulation performance.

(2) The main way to enhance heat transfer is to expand the heat transfer surface. Change flow conditions.

Add additives to the fluid. Change the condition of the heat exchange surface.

Small diameter tubes are used instead of large diameter tubes, and oval tubes are used instead of round tubes to improve the surface heat transfer coefficient. Change the mode of energy transfer and rely on external force to strengthen heat transfer: (3) The main way to weaken heat transfer is to wrap thermal insulation materials on hot and cold equipment.

Making the outer shell of a thermal device a vacuum sandwich changes the radiation characteristics of the surface.

5.1 How much energy is a calorie?

In exercise and diet, we often encounter several words for calories: calories, kcal, calories, kilojoules, joules. Calorie unit conversion; kilojoules Cal = Calories kilocalories = Kcal 1 kcal = 1000 calories 1 kilojoule = 1000 Joules 1 kcal 1 kcal 1 calorie = 1000 calories 1 kcal / 1 kcal / 1 calorie (kcal) = 4.184 kilojoules (kJ ) 1 calorie = 4.182 joules. In exercise and diet, we often encounter several calorie words: calorie, kcal, calorie, kilojoule, joule. Calorie unit conversion; kilocalorie = calorie kcal = kcal 1 kcal = 1000 Calorie 1 kJ = 1000 Joules 1 kcal 1 kcal 1 calorie = 1000 kcal 1 kcal / 1 kcal / 1 calorie (kcal) = 4.184 kilojoules (kJ) 1 calorie = 4.182 joules.

6. Food calorie table

This question is asked at a high level.

The calories of food are the energy that the food can provide, which is "calories", also called calories. To measure the number of calories provided by a serving of food, you burn the food in a container and measure the heat produced.

One calorie unit is equivalent to heating 1 liter of water to 1 degree. Everyone needs energy every day, and the source of this energy is food. Each type of food can provide different amounts of energy at the same weight.

For example, 1 gram of carbohydrates has 4 calories, and 1 gram of fat has 9 calories. So neither calories nor fat make us obese.

We only become fat when the food we eat provides more energy than we consume every day. According to statistics, for every 3,500 extra calories you eat, you will gain 1 pound of weight.

Similarly, if you consume 3,500 calories, you will lose 1 pound. If we maintain a balance between the food we eat and the energy we expend each day, our weight will stay the same.