Modern people pay more and more attention to diet, and calories have become the most important food label for many people. This is originally a physical term, and 1 calorie is equivalent to 1 g of energy required for the rise of purified water 1℃. The field of food science likes to use the unit of "kilocalorie" to facilitate calculation. Among the three major nutrients, carbohydrates and protein can generate about 4 kilocalories per gram, while the energy density of fat is much higher, and each gram of fat can generate about 9 kilocalories, which is why the human body stores most of the excess energy in fat, but the result of doing so has brought endless troubles to us modern people who have no worries about food and clothing.

According to the popular saying now, the total energy contained in the food a person eats every day minus the total energy consumed this day is the net energy value of this person. This value is closely related to fat. If this value is positive, excess energy will be converted into fat, and people will become fat, otherwise they will burn fat to fill the vacancy. So many people who plan to lose weight decide how much food to eat according to the total calories they consume every day. The question is, is the algorithm of food calorie still19th century American chemist Wilbur? It was first put forward by WilburAtwater and has not been revised for many years. Recently, many scholars have pointed out that this algorithm is outdated, and the actual situation is far more complicated than the numbers printed on food packaging bags. North Carolina State University nutritionist Robert? RobDunn wrote a review article in Scientific American magazine published in September this year, explaining the reasons in detail.

According to Professor Dunn, there are three factors that determine that the calories of different foods have completely different effects on different people. First of all, people have different digestive abilities. The most common reason is that the types and contents of digestive enzymes are different, which is easy to understand. There are also some less common reasons that can lead to this result. For example, at the beginning of the 20th century, some people studied the length of the large intestine of different ethnic groups and found that the length of the large intestine of a certain ethnic group in Russia was 57 cm longer than the average length of a certain ethnic group in Poland! The large intestine is an important organ for nutrient absorption, and this difference shows that there are great differences in the digestive ability of different people.

People's digestive ability is not only related to their own physiological characteristics, but also related to the types of intestinal flora. Human intestinal flora can be roughly divided into Firmicutes and Bacteroides. Fat people have more intestinal flora than the former, probably because members of Firmicutes are better at absorbing nutrients from food residues.

Secondly, the digestibility of different foods is also different. Food is life before it becomes a human dish. They are not born for human beings and have their own behavioral logic. For example, the stems and leaves of many plants contain toxins to prevent animals from eating them. Although the food and vegetables cultivated by human beings for many years have little toxicity, the cell wall of plant cells is still difficult to digest, and this barrier can only be broken through external grinding, high temperature treatment or the action of some special enzymes.

Another interesting example is fruits and seeds. Plants evolved fruits to attract animals to eat and spread seeds, but the seeds contained in fruits must stand the test of animal digestive tract, otherwise all previous efforts will be in vain. This is why most fruits are high in sugar, easy to digest and attractive to animals. Although seeds are nutritious, they are extremely difficult to digest. Janet, a scientist at the US Department of Agriculture? JanetNovotny and her colleagues published a paper in the American Journal of Clinical Nutrition last year. By analyzing the excrement of volunteers, it is proved that the actual net absorption of almonds with a calorie value of 170 kcal is only about 129 kcal, and nearly 1/4 of the energy cannot be absorbed by human body.

Third, the digestion process itself also needs to consume energy. The energy required by human body to digest different foods is also very different, which leads to great differences in net energy values of different foods. For example, monosaccharide is the most digestible food and consumes almost no energy. Long-chain carbohydrates composed of monosaccharide molecules end to end need to consume some energy to break chemical bonds, which is why eating starch with the same calorific value is much healthier than eating sugar directly. Fat is also a digestible food, but it is more difficult in protein. At the same calorie, it may take five times more energy to digest protein than to digest fat.

It is worth mentioning that not only the digestive process needs energy, but also the human body must guard against germs from food. If you encounter "dirty" food, the human immune system will be mobilized to monitor the enemy's situation, which also requires some energy consumption. If there are too many "enemies" in food, the human body will even start an emergency system to excrete undigested food through "diarrhea". Needless to say, the net energy value at this time has to be calculated separately.

In short, the calorie value of food is only an estimate, and the calorie effect of different foods is very different from each other. If you want to control your weight, you should not only reduce your calorie intake, but also try to reduce your intake of monosaccharides and refined processed foods, and eat more coarse grains, lettuce and protein.

(Author: soil motorcycle)