Counting Calories

A cartoon of a flapper.

Calorie counting started long before the thin, elegant image of the flapper made headlines in 1920s. Image courtesy Library of Congress.

Following World War I a sea change in fashion encouraged women to take thyroid extracts, exercise, and buy rolling pins that promised to “roll off the fat.” And when stronger weight loss measures were called for, calorie counting promised a failure-proof, “scientific” approach to weight loss. Yet the long life of the calorie began not in the mirror but in 19th-century laboratories and factories, an unlikely origin for something so closely tied to dieting. The word calorie—a French-derived term denoting “unit of heat”—grew out of the notion of caloric, a fluid believed to embody heat. While caloric as a theory faded, the calorie became indispensable in the study of heat and energy in machines—especially steam engines—and later in human machines as part of food and metabolic studies. But by the end of the 1920s the calorie had become an enduring feature of American nutrition science and dieting culture, for better or worse.

Chemist Wilbur Olin Atwater brought the calorie from Germany to the United States. Born in Johnsburg, New York, in 1844, Atwater obtained a Ph.D. in agricultural chemistry in 1869 from Yale University’s Sheffield Scientific School. He then spent two years in Germany, then the vanguard of agricultural science and physiology. Upon his return Atwater taught chemistry at East Tennessee University (now the University of Tennessee) before moving on to a lifelong professorship at Wesleyan University.

Atwater, a Victorian with a solemn countenance, pursued the study of the energy requirements of the human body at rest and in action. (Ironically, the only exception to Atwater’s otherwise austere appearance was his ample midsection, which stretched the vest of his three-piece suit.) His work on calories was part of a broader development in American nutrition science. During the 1860s scientists began to investigate systematically the chemical composition of foods, and in the 1910s and 1920s they identified a host of vitamins and minerals essential for survival. But they were particularly interested in measuring the energy (heat) value of foods, at first for livestock and later for humans. Knowledge about the heat value of foods, however, was incomplete without answers about how the body expended that energy once consumed.

From Farms and Factories to War

Large-scale agricultural production and industrialization provided the backdrop against which 19th-century scientists in western Europe and the United States studied energy expenditure. Physiologists and nutritionists argued that better nutrition and healthier bodies would result in more efficient workers, greater industrial output, and better work discipline. In turn-of-the-century Germany physiological studies on human fatigue were part and parcel of managerial aims to yield maximum productivity and efficiency in labor. In the United States the same might be said about experiments investigating calorie and nutrient requirements. In the mid-1880s, not long before the mechanical engineer Frederick Winslow Taylor began to promote his factory time and motion studies and efficiency principles for labor—later called Taylorism—Atwater was conducting dietary studies on bricklayers in Massachusetts and Connecticut. He wanted to know how many calories and grams of nutrients bricklayers required in order to perform their work—information of particular interest to industrial managers. An 1886 article published in a general-interest magazine by Edward Atkinson—industrialist and admirer of Atwater’s work—showed that this was a science already moving beyond the lab and into the market. Brickyard managers and proprietors, according to the magazine The Century, used these studies to learn which diets would “promote the largest production of brick per man at the lowest cost to the employer.”

Atwater expertly promoted his own work on calories. From 1887 to his death in 1907 he wrote extensively about calories in The Century and in many U.S. Department of Agriculture (USDA) tracts. In these publications Atwater explained what the calorie was, how many calories various foods contained, and the number of calories one should consume according to one’s sex, age, and activity level. A “woman with light exercise,” for example, required 2,300 calories per day, while a man with a corresponding activity level needed 2,830 calories, according to a Century article Atwater wrote in 1888. Part of his purpose in promoting calorie knowledge was to guide readers on what and how much they ought to be eating. But the chemist’s earnest faith in education and in applying knowledge gleaned from empirical studies to everyday life was informed by his moral judgments about how one should eat: Atwater, the son of a Methodist minister, zealously preached the gospel of thrift.