The calorie we’re familiar with started

 The calorie we’re familiar with started 

to enter American vocabulary in the late 19th century, according to James Hargrove, an associate professor emeritus of food and nutrition. 

The American chemist Wilbur Olin Atwater, who is considered a pioneer in nutrition studies, described the calorie to American audiences in a magazine called “Century” back in 1887. 

Hargrove wrote that Wilbur chose this as an energy unit for food because “the Calorie was the only named energy unit that existed in English dictionaries of the time.” Although the joule was “proposed as an electrical unit in 1882,” it had not yet entered our lexicon. The term “Calorie” was also included in an 1894 issue of Farmers’ Bulletin, a publication from the U.S. Department of Agriculture

Calories ended up being used as the unit of USDA food energy content in tables that Atwater developed at the end of the 19th century, Hargrove explained to Marketplace over email. 

As it turns out, even a calorie has an economic function. “In the old days, people were plowing fields behind horses, and knowing how much food was needed to do that work by the man and the farm animal was very important to the farm economy,” Harnack said.