There is a question: how the caloric content of products is calculated
Calorie counting is one of the main techniques used for weight loss . But how do specialists in the field of food determine that, say, in a cereal bar is 100, not 300 or 350 calories? We’ll try to figure it out right now.
The first thing you should know: calorie is a unit of energy, not an indicator of the weight or density of nutrients. However, the calories that we see on packages are kilocalories (kcal). “One kilocalorie is the amount of energy needed to heat one kilogram of water per degree Celsius,” says Live Science Grace Derocha, a nutritionist at Blue Cross Blue Shield in Michigan.
All the calories contained in our food come from three macronutrients: fats, carbohydrates and proteins. In many countries laws have long been in force, requiring manufacturers of packaged products to indicate on the labels how many calories are contained in these products. One way to do this is a special tool called a bomb calorimeter.
“This tool directly measures the amount of energy that the product contains,” explains Ruth MacDonald, a professor at the University of Iowa State. To use it, scientists place the food in question in a sealed container surrounded by water, and gradually heat the container until the food is completely burned. Then they fix the rise in water temperature to determine how many calories are in the product.
But bomb calorimeters are not the only way to calculate the calories contained in the product. Experts in the food industry often rely on the calculation developed in the 19th century by an American chemist, Wilbur Atwater.
Etwether came up with a technique known as the 4-9-4 system, because calorimeters did not take into account that people also lose calories through heat, plus some calories emerge naturally from their bodies with urine and feces. The researcher found that you can overcome these limitations by first calculating the number of calories in different foods, and then analyzing the composition of the stool to see how many calories went out of the body intact.
Experiments have shown that proteins and carbohydrates contain about 4 calories per gram, and fats – about 9 calories per 1 gram. From here, as you can now understand, and the digital name of the system. By the way, according to Etwater, alcohol contains about 7 calories per gram.
However, despite the fact that over a hundred years, food chemists have significantly improved the calculations of the scientist, some experts are sure that the system could never be called accurate. A 2012 study published in the American Journal of Clinical Nutrition showed that the energy content of certain foods (eg, nuts) can not be calculated using the 4-9-4 system. Plus, it is worth considering that when indicating the calorie content of the product on the label, an error of up to 20% is officially allowed.
“And even if such an error did not exist, the method in any case does not take into account the process of digestion, but assumes a complete conversion of nutrients into energy,” says Ruth McDonald. “This does not happen in humans, although our bodies are quite effective in the sense of restoring energy from food.”