Those who receive nutritional counseling are generally sent home with a task. These individuals will meticulously record all the food and drink they consume over the course of a week. During their next consultation, the expert will input this data into a computer and quickly determine the body's energy supply derived from food. This value is derived by neatly叠加ing various data together. If anyone doubts this, they can recalculate it themselves afterward. This well-known table of food caloric content is not subject to our will. Through it, we can know how many calories we wolf down every day. This data can even be precise to several decimal places. People often compare this data with another table, which indicates how many calories are sufficient per day for a person engaged in medium-intensity physical work. For many, the next natural step is to quickly formulate a calorie-saving plan tailored to their own situation.
But where do these arbitrary data actually come from? How do people determine exactly how many calories are in a certain food, and how many of those are released in the human digestive tract? After all, the digestive process is far more complex than an engine's combustion process, and one cannot make reckless assumptions by simply comparing the two scenarios. Not every substance that generates heat can provide energy to the body. The best example is gasoline. It can definitely power a car, but if someone were to ingest it, the result would likely be disastrous.
The caloric content of a substance is collected using a so-called special calorimeter. First, the substance to be measured is placed in a metal cylinder containing a hot metal wire. The substance in the cylinder is then heated until it burns completely and is fully carbonized. The cylinder is then placed in a water container, and the amount of heat (caloric value) released by the substance is calculated by measuring the increase in water temperature. Undoubtedly, this method makes it easy to measure the caloric value of substances like kerosene, which leave only ash and exhaust fumes after combustion. Unlike the combustion process, the human body digests food systematically, and a large amount of residue is excreted after metabolism. It is not surprising, then, that the energy the human body obtains from digesting food is significantly less than the theoretical value obtained from a calorimeter.
Therefore, it is not enough to simply calculate how many calories we consume; we must also consider how many of those calories are excreted. It may take professionals many years of effort to convince readers of this truth: what we eat is not as important as how much of what we eat is digested and absorbed. Human excrement is not composed only of undigested food, but also includes a large portion of intestinal cells and gut flora that have separated from the body. The quantities of these two are immense and difficult to calculate. Perhaps because filling a calorimeter with feces would affect the experimenters' appetites, they generally only estimate the caloric content of excrement. From a physiological perspective, this estimation is a theoretical value for human energy expenditure. When it is reflected in an energy consumption table, it is somewhat demanding on the human body.
But the problem does not end there. There are many more questions we can list here: the composition of the food we eat on a daily basis fluctuates. For example, due to excessive fertilization, vegetables have an unusually high water content; the nutrient composition of each apple varies; and no mineral water contains all minerals. In nature, it is normal for the nutrient composition of food to fluctuate. But in the hands of incompetent nutritional consultants, this becomes a burden in our lives. They like to use average calculations, even though the vitamin composition of an apple can vary greatly depending on location and other factors.
In addition, we can give another example. Many people not only eat cherries but also love baked cherry pies. How can one determine the energy value of a cherry pie? Of course, the computers in the nutrition consultants' offices will have "precise" values. But are these data really reliable? The composition of a cherry pie can vary greatly depending on the bakery. This completely depends on what kind of fat the baker adds to the dough or what the filling of the cherry pie is. Did the baker use homemade cherry jam or a store-bought product? Is the jam high in cherry content or in artificial flavors and substances? Is this filling very thin (indicating high water content and low energy value) or very thick? How much does each cherry pie actually weigh, 75 grams or 150 grams?
Our in-depth questioning of the cherry pie is also fully applicable to other foods we eat daily. The soup we have for lunch in the company cafeteria is nutritionally different from the soup we drink at a restaurant in the evening. How many slices of sausage did you add to your sandwich at noon? Were the slices thick or thin? What was the product composition of these sausages when they were manufactured in the factory? Did you spread butter on your bread? How many grams? For nutritional consultants, these are not issues. The nutritional composition plans and food caloric content tables they provide for others are very precise—regardless of whether they are accurate or not, the calculation is done immediately. Even more bizarrely, the computer apparently knows the weight of pastries from Berlin and knows the exact amount of food the client consumes in a meal. But do you remember one thing: when you were eating in the cafeteria, how much of your meal did you leave and throw away? Can you recall it accurately?