ChemMatters: The Science Behind Calories and Nutrition Facts Labels

Our latest ChemMatters episode explains the science behind calories and nutrition facts labels. Find out how scientists first determined the calorie content of food in the 1800s, and how fat, protein and carbohydrate levels on nutrition facts labels are found today.

The video explains that the calorie content of food was determined in the late 1800s by chemist Wilbur O. Atwater. Atwater built a four by eight foot device called a respiration calorimeter, which was big enough to allow a person to step into it! It measured the amount of heat they released, the amount of oxygen they consumed and the carbon dioxide they gave off after eating a variety of foods.

Using this device, Atwater was able to measure the precise amount of energy contained in thousands of food items. He found that carbohydrates and proteins were worth 4 Calories per gram and fats about 9 Calories per gram. This 4-9-4 rule is at the heart of how nutrition facts labels are determined today.

Produced by the American Chemical Society
Animation and motion graphics by Sean Parsons
Directed by Adam Dylewski and Sean Parsons

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