Public Release: 

For the holiday weight-gain season: The chemistry behind calorie counts and nutrition labels

American Chemical Society

WASHINGTON, December 17, 2012 -- With the holiday season a high-risk period for packing on unwanted pounds, the American Chemical Society (ACS) today posted a new video that may lend perspective on this year's battle of the bulge. Produced by the world's largest scientific society, it explains the science behind the calorie counts and other information on those Nutrition Facts Labels on food packages. Available at, the video tells the story of how scientists first determined the calorie content of food in the 1800s, and how scientists determine fat, protein and carbohydrate levels in foods 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, which is about 1/28th of an ounce. This 4-9-4 rule remains embodied in today's Nutrition Facts Labels.

The video, from the award-winning Digital Services Unit in the ACS Office of Public Affairs, is based on an article in the latest issue of ChemMatters, ACS' quarterly magazine for high school students.


ChemMatters has been connecting chemistry to our everyday lives for the past 28 years. Published quarterly by the ACS Office of High School Chemistry, each issue contains articles about the chemistry of everyday life and is of interest to high school students and their teachers.

For additional entertaining video podcasts from ACS, go to The Bytesize Science series is produced by the ACS Office of Public Affairs.

The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With more than 164,000 members, ACS is the world's largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.

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