Athens, Ga. – While enjoying a Thanksgiving dinner with friends and family, most try to avoid thinking about the seemingly unending number of Calories they're consuming.
It probably never crosses their minds, however, to think about why food is measured in Calories.
James L. Hargrove, associate professor of foods and nutrition in the University of Georgia's College of Family and Consumer Sciences, said many nutritionists aren't even sure of the true origin of the Calorie (or why it's supposed to be capitalized).
"We all teach this unit, and nobody knows where it came from, not even the historians of nutrition," he said.
After this realization, Hargrove began studying the origins of the Calorie. He details his findings in a study to be published in the December issue of the Journal of Nutrition.
Formally, a Calorie is a measure of the amount of energy required to heat one kilogram of water one degree Celsius. It was first used in engineering and physics, but eventually found its niche in nutrition, where it is used to measure the amount of energy food contains.
Hargrove found that there's some controversy about who "invented" the Calorie. Some references show that two Frenchmen, P.A. Favre and J.T. Silbermann, invented the Calorie in 1852. Other texts state that a German physician, Julius Mayer, effectively invented the Calorie in a study he published in 1848.
Hargrove credits the French chemist Nicholas Clement with the invention, however, citing lecture notes from Clement that define the term as early as 1819.
He credits Mayer with beginning a dialogue about food as an energy source. Before Mayer's time, people thought that energy was God-given; they made no concrete connections between food they ate and the energy on which their bodies ran.
Despite the confusion over who invented the unit, Hargrove notes that the Calorie as a nutritional unit came to the U.S. by way of a man named Wilbur Atwater in 1887. Shortly afterward, the science of nutrition began to take hold in the U.S.
A popular early nutrition text published in 1918 by Lulu Hunt Peters outlined the first methods of counting Calories. In her bestseller, Diet and Health, with the Key to the Calories, Peters outlined 100-Calorie portions of many foodstuffs and preached counting Calories as a way to regulate weight.
Hargrove notes that one common misunderstanding about the Calorie is why it is spelled with an uppercase "C" rather than a lowercase "c." Owing to the obscure origins of the measure, there was confusion about whether or not a calorie was defined as the amount of heat required to raise one kilogram of water one degree Celsius or one gram of water one degree Celsius. As the Calorie became popular in nutrition, it became more practical to measure the amount of kilograms. To denote this, a capital "C" refers to a kilogram calorie, while a lowercase "c" refers to a gram calorie.
"In food and daily energy, we use so much energy that if you measure in gram calories, you're talking about two million calories a day," he said. "And who wants to think about that?"
Journal of Nutrition