What is a calorie?

I was at a party this weekend and someone asked me this question and I thought it’s not exactly the easiest thing to define. So let me try to help you understand it a little better and maybe it will then help you understand your food label a little more.

The most commonly known definition of a calorie is the energy needed to raise the temperature of 1 gram of water through 1 °C. Probably not what you were expecting to hear right? And a lot of science and research is involved in how this original definition became the calories that we today know on the standard US Food Labels. So how do we simply understand that connection between that definition and what we eat? Well, energy used by the body is ultimately derived from the energy contained in the fat, carbs and protein we eat. So every time you eat, imagine energy being released into your body as heat. See the connection back to the original definition kind of? It’s confusing. And I don’t think you technically need to know that to the benefit of your health. The most important calorie information to me is how calories are calculated to give you totals on your food labels.

A food label for a Frozen Pizza.

TOTAL CALORIES IN 1 SERVING (1/3 of the pizza) = 340 calories

TOTAL FAT = 13 grams

TOTAL CARBS = 39 grams

TOTAL PROTEIN = 19 grams

1 gram of fat has 9 calories. So multiply 13 grams X 9 calories = 117 calories

1 gram of carbs has 4 calories. So multiply 39 grams X 4 calories = 156 calories

1 gram of protein has 4 calories. So multiply 19 grams X 4calories =76 calories

Then add that all together. 117 calories from fat+156 calories from carbs+ 76 calories from fat = 349 total calories. Pretty close to the 340 calorie total stated on the package for 1/3 of pizza. The total when using the 4-4-9 method will always be close to the total calories the package states. It may be exact and it may be a little off because this is an overly simplified method and FDA regulations for U.S. foods say individual companies can use different approved methods for determining Calories for their food. It will always be close, but maybe a few calories different. This is another reason why it’s important not to live and die so strictly to the calories in vs. calories out philosophy.

So you see where the calories come from? And kind of how they are calculated? And of course every grams of fat, carbs and protein offer different nutrients and vitamins and act different in the body. Which we’ll talk more about in a later lesson:)!

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