What are calories?

What are calories?

Definition of what constitutes a calorie appears to be easy: according to the majority of textbooks in science, that's how much energy required to raise one gram water to 1 degree Celsius. But how does that relate in relation to caloriecounts we see all over everything from fast food menus to snack bar nutrition labels

If we take a look at caloriecounts, we're typically trying to figure out the amount of energy we're pumping into our bodies. However, a label on a food item will not give you that, at least not exactly. There are too many factors in play, many that are influenced by the person's physical physiology, and others of which we're still in the process of determining.

Think about this: In 2020 the almonds suddenly seemed to have around 30 percent less calories than they had in the year before. Both walnuts and cashews saw a similar drop of energy density. Nuts themselves didn't change, obviously, but the method used to calculate calories did.

This is due to the fact that it's because the FDA and USDA frequently use the same method used for centuries to measure calories. Originating in the late 19th century (though exceptions are made if there's more recent research, such as for some nuts). The late 18th century Wilbur Atwater, who was a researcher, wanted to quantify the energy content in foods by burning the substance and calculating how much energy was present in it and then feeding similar food to individuals and then observing how much energy is contained in their poop and pee. The difference between energy in and energy out, or so was the basis for the calorie-calculating figures that we have today for macronutrients: nine calories in one gram of fat, and 4 calories in grams of carbohydrate and protein.

In the 19th century, this was a major leap forward in the understanding of energy density of food. However, in the 21st century, the results don't match up.

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A calorie of fat in a nut for example, doesn't appear to mean the exact as an calorie in animal fat. While it's unclear why this happens and why, it's likely that our bodies don't process all foods equally, so certain calories remain within the food and exit in our poop, never having had any effect on our waistlines. (We need to note that the study on the calories in nuts was partly funded by various board members, although the interested parties didn't design or perform the studies themselves).

The idea of bioavailability just recently become a subject of research, therefore there's a lack of data about what other types of food items we're ill-informed about measuring. We've learned, for example cooking food tends to help make the nutrients within it more easily accessible. We also know that our personal microbes in our gut help determine how much energy we extract from our food, like by breaking down the cell walls in certain vegetables. The Atwater system does not account at any point for cooking food much less the method you use to cook it nor does it account for various bioavailability differences between kinds of food. It's all about the number of grams of protein, fat, or carbohydrate in the food.

The new studies on nuts don't utilize a more sophisticated technique that Atwater employed. The researchers gave almonds (or cashews, walnuts or even cashews) to the participants, then examined their poop to determine the amount of energy consumed. However, the USDA researchers were compelled to study one food specifically.

Until we find a better method to quantify the energy contained in each food category in the near future, a calorie actually, is a number we've assigned arbitrarily to food items. Try not to take it too seriously.