What are calories?

What are calories?

Definition of what constitutes a calorie is simple. According to most textbooks on science, It's the sum of power needed to raise one gram of water by 1 degree Celsius. How does this apply to the caloriecounts you see on everything from fast food menus to nutrition labels on snack bars

When we think about caloriecounts, we're generally hoping to understand the amount of energy we're pumping into the body. But a nutrition label cannot provide that, at minimum, completely. There are too many variables to consider, many of which depend on the person's physical physiology, and others that we're still in the process of determining.

It is worth noting that beginning in 2020, nuts suddenly looked like they had around 30 percent less calories than they did the year prior. The walnuts and cashews experienced similar declines in energy density. The nuts themselves did not change, naturally, but the method used to determine calories changed.

It's because the FDA and USDA frequently use an outdated method for measuring calories. It was developed in the 19th century (though some exceptions are made when there's more current research available, like for those who are nuts). In the late 19th century, Wilbur Atwater, decided to gauge the amount of energy in food by burning the substance while determining how much energy was in it and then feeding the same food items to people and then observing how much energy was in their poop and pee. The difference between the energy that was in and the energy that went out, in a sense and the calculation of calories, was what led to the numbers we use for macronutrients today 9 calories in a gram of fat, and four in one gram of carbohydrate or protein.

In the 19th century this was a huge leap in the understanding of energy density in food. However, for the 21st century it's not quite what we expected.

[Related: The truth about measuring calories]

For instance, a calorie of fat in a nut, for instance, does not appear like the same as a calorie made from fats from animals. Although it's not clear the reason for this however, it appears that our bodies aren't able to digest all food products equally, so certain calories remain in the food, and then go into our poopand never have any impact on our waistlines in any way. (We are reminded that the research into the calories found in nuts was partially funded by various nuts boards, but the parties involved didn't create or conduct the research themselves).

Bioavailability is a concept that has only recently been made a focus of study, and there's not much information yet on what other types of food products we're not measuring. We know, for instance that cooking food appears to make the nutrients inside the food more readily available. We also know that our personal microbes living in our intestines help determine how much energy we extract from our food and this is done by breaking down the cell walls in certain vegetables. The Atwater system doesn't account at anything for cooking food and even less, how you cook it and it doesn't take into account differing bioavailability of different kinds of foods. It just goes by how many grams of protein, fat, or carbohydrates are present in the food.

The new nut research doesn't employ a more sophisticated method than the one Atwater employed. Basically, the researchers gave almonds (or walnuts or cashews) to the participants, then monitored their poop levels to determine the amount of energy being absorbed. It's not that the USDA scientists wanted to study one food group in particular.

In the meantime, until we discover a better method of quantifying the amount of energy within a specific food category in the near future, it is believed that a calorie actually, is a number we've assigned to food items. Do not think about it too much.