What are calories?

What are calories?

Defining a calorie isn't hard: according to the majority of science textbooks is the energy needed to increase the weight of one gram of liquid by 1-degree Celsius. However, how does this relate to the caloriecounts you see on everything from fast food menus to snack bar nutrition labels

When we consider caloriecounts in the context of calorie count, we're generally hoping to understand how much energy we're pouring to our bodies. However, a label on a food item cannot be able to provide this, at the very least, accurately. There are too many variables involved, some of that depend on the physiology of an individual, as well as some of them are still working out.

Consider this: Starting in the year 2020 the almonds suddenly appeared to contain around 30% less calories than they did the year prior. The walnuts and cashews experienced the same drop in energy density. Nuts themselves didn't change, obviously, but the method employed to determine calories changed.

This is due to the fact that the FDA and USDA typically still use the same method used for centuries to measure calories. originating in the late 19th century (though exceptions are made if there's more current research on the subject, like with these nuts). In the late 18th century Wilbur Atwater was the first to quantify the energy content in foods by burning the substance while determining how much energy was contained in it as well as feeding the same food to the people and determining how much energy was contained in their poop and urine. The difference in energy that was in and the energy that went out, so to speak has become the calorie-calculating numbers that we currently use for macronutrients 9 calories per gram of fat, and four calories in a gram of carbohydrate and protein.

For the 19th century this was an enormous leap in the understanding of energy density of food. However, for the 21st century, the results don't match up.

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A calorie of fat in a nut for instance, does not appear to mean the exact as the calorie in animal fat. Though it's still unclear the reason for this, it seems that our bodies aren't able to break down all food items equally, which means some calories remain within the food, and then go into our poop. However, they haven't an impact on our waistlines. (We should note here that the study on the calories in nuts was partially funded by various nut boards, though the interested parties didn't design or conduct the research).

Bioavailability is just recently become a subject of investigation, and therefore we don't have any information about other foods we're not measuring. We know, for instance that cooking food can seem to make the nutrients that are in it more readily available. We also know that our individual microbes within our gut help determine how much energy we extract from our food, like by dissolving cell walls within certain vegetables. The Atwater system doesn't account at any time for cooking food, nor does it consider the method you use to cook it nor does it consider differences in bioavailability between different types of food. It's just the number of grams of protein, fat, or carbohydrate in the food.

The new nut studies don't utilize a more sophisticated approach than the one Atwater employed. The researchers fed almonds (or cashews or walnuts) to the participants and they measured their poop for the amount of energy consumed. The difference is that USDA researchers were compelled to look at one food specifically.

Until we find a better method of quantifying the amount of energy contained in each food group and a calorie is, in reality it's a number we've given to food items. It's best not to consider it a serious matter.