Hargrove, in one paper, wrote that Americans

 Hargrove, in one paper, wrote that Americans

 were interested in managing their weight back in the day, as they still are, and the calorie was also included in articles and books, including the best-selling book “Diet and Health with Key to the Calories” from 1918. 

But not everyone was on board with this unit of measure, with the British advocating for the joule, named after James Prescott Joule, starting around the 1880s. “The Calorie was a ‘French’ unit, and the British argued that it was imprecise,” Hargrove said over email.

The British won out decades later. The International System of Units (SI), also known as the modern metric system, was launched in 1960 and had adopted the joule. 

“European advisory committees used that unit for their food labels, and the Calorie was abolished,” Hargrove said. 

Why prioritize the joule or kilojoule over the calorie? Well, there are several base units included in the International System of Units (SI), also known as the metric system. A joule is derived from other units within the metric system, according to the Food and Agriculture Organization of the United Nations. (A joule equals 1 newton of force over a distance of 1 meter).  

“The calorie cannot be derived directly from the basic SI units without using an experimentally determined factor, whereas the joule corresponds with the energy measurements in all branches of science on which the nutritional sciences depend,” explained FAO.