How Calories Are Calculated


The latest episode of ChemMatters by Bytesize Science, is all about nutritional facts — how they are determined and placed on a label and what they mean for you. 

With more than one-third of U.S. adults considered obese, nutritional labels are an important way to let consumers know how many calories any given food gives you, so you can make smarter choices.

What is a calorie and how is it measured?

The calories on nutritional facts are actually kilocalories. One Calorie is the amount of energy that is required to heat one kilogram of water 1 degree Celsius at sea level.

Calorie content was first determined in the 1800s by chemist Wilbur O. Atwater who made a 4-by-8-foot device called a respiration calorimeter. This device could measure the the amount of heat released, oxygen consumed, and carbon dioxide a person gave off after eating a variety of foods. Atwater learned that carbs and proteins were worth 4 calories per gram and fats were worth 9 calories.  

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