This Doctor Pioneered Counting Calories a Century Ago, and We’re Still Dealing With the Consequences

In 1909, more than a decade before the 19th Amendment would grant her the right to vote, Lulu Hunt Peters had already achieved a rare status for a woman of her time. She earned a doctor of medicine degree from the University of California, when fewer than 5 percent of American medical students were female, and she was the first woman to intern at Los Angeles County General Hospital; she led its pathology lab for a time and later served as chair of the public health committee for the California Federation of Women’s Clubs in Los Angeles. The role, wrote the Santa Cruz Evening News, came with “more power than the entire city health office.” She lectured frequently about public health and child nutrition.

Over the next decade, though, what Peters came to regard as her greatest triumph was more personal than professional. As she entered her 40s, Peters used stringent and unrelenting discipline to slim what she described as her “too, too solid” body by dropping 70 pounds. That was what she really wanted to tell people about, with a fervency that approached the messianic. She began tailoring her lectures toward the holy grail she had discovered, a tool that she saw as the key to her weight loss: something called the calorie.

Familiar territory even to schoolchildren today, the calorie was, more than a century ago, a niche concept just beginning to emerge from the laboratory and into public view. Peters was about to supercharge that evolution, in the process turning the meaning and use of the calorie on its head and spurring its transformation into one of the most enduring and significant health concepts of the modern day. The calorie gave the public its first penetrating view inside the foods they ate, providing an elementary understanding of nutrition. But it would also go on to torment millions, enrich corporations, inspire generations of advertising campaigns, provoke widespread guilt and pride, and even, some argue today, lead Americans, fat gram by carb gram, calorie by calorie, into epidemic levels of obesity, by instructing the masses to focus on calories rather than on nutrients and steering them toward highly processed carbohydrates.

cover of Lulu Hunt Peters book — The cover of Lulu Hunt Peters' book *Diet and Health*.

Peters ended up distilling her passion for calorie counting into a slim handbook, which was published in 1918 and went on to become the first diet best seller in history. Titled Diet and Health With Key to the Calories, Peters’ book did not stint on humor and playfulness. She engaged her 10-year-old nephew (“the little rascal”) to contribute whimsical stick-figure illustrations, and she made up satirical names like Mrs. Ima Gobbler and Mrs. Tiny Weyaton for hapless members of what she in later works would call the “Friendly Fat Fraternity” (epithets and terminology that would not go over benignly today). But throughout, she paid constant obeisance to the invisible, ineffable calorie. “You should know and also use the word calorie as frequently, or more frequently, than you use the words foot, yard, quart, gallon and so forth,” she wrote. “Hereafter you are going to eat calories of food. Instead of saying one slice of bread, or a piece of pie, you will say 100 calories of bread, 350 calories of pie.”

The idea had a novelty and simplicity that sparked a movement. By 1922, Diet and Health reached the best-seller list and remained there for four years, nestled among works by Mark Twain and Emily Post. And just like that, a century of calorie-counting began—for better or, as it’s become increasingly clear, for worse.

Portrait — Having lost 70 pounds, Peters wanted to help others reduce.“I will save you; yea, even as I have saved myself and many, many others,” she wrote. Pictorial Press Ltd / Alamy Stock Photo

When Peters started proselytizing for the calorie in the mid-1910s, the concept was so new to the general public that she had to tell her readers how to pronounce the word. (Kal’-o-ri, she explained, adding coyly that yes, calories are kosher.) But researchers had been studying the calorie for decades, for reasons that could not have been more different from Peters’. The calorie, based on the Latin root “calor,” meaning heat, was first identified and used by the French chemist and physicist Nicolas Clément, who described it in the 1820s as a measure of heat that could be converted into energy. Specifically, it was defined as the quantity of heat needed to raise the temperature of one kilogram of water by one degree Centigrade. Clément was not concerned with food or body weight, but with how to measure the steam energy needed to operate engines. In the decades that followed, though, other European scientists extended the idea to the human body, using the logic that the body is also a machine that burns fuel (food in place of coal) to create energy. By the late 1800s, German physiologists were measuring the energy values of foods using Clément’s methods, and using a “respiration calorimeter”—an enclosed chamber that measures an animal’s oxygen and carbon dioxide, as well as heat given off—to track how that energy was actually processed in the body.

Beginning in 1869, and again in the 1880s, a New England chemist named Wilbur O. Atwater went to Germany to study the emerging science of nutrition. He returned with an idea that would revolutionize how Americans view food. The calorie, he believed, could help improve dietary health at a time when malnutrition, not obesity, was the greater problem. And as a fitting addition to the ongoing Industrial Revolution, which was showing how science could transform daily life, the calorie could also make American workers ever more productive—and at a low cost.

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Portrait / Machine — Chemist Wilbur O. Atwater built the first American respiration calorimeter, a copper-lined box that estimated a person’s calorie expenditure by measuring the heat they produced while living inside the device for as many as 12 days at a time. Right: GL Archive / Alamy; Left: Volgi Archive / Alamy

The “father of American nutrition science,” as Atwater became known, wrote fervently in the 1890s about improving “the intellectual and moral condition and progress of men and women” by establishing a standardized formula for deriving calories from various foods, calling them “physiological fuel values.” This would allow Americans to choose their foods by the numbers—rather than by guesswork or emotion—and thereby get the biggest nutritional bang for their food buck. “In our actual practice of eating we are apt to be influenced too much by taste,” he wrote. The solution was to “regulate appetite by reason,” aided by his lists of calories. His work has proved so durable that nutritional labels on every grocery-store item today hark back to it. Calories are still based on the heat they generate, though scientists no longer subject food to a calorimeter, because their nutritional contents can be calculated by the “Atwater system,” which assigns a calorie value to each gram of protein, fat and carbohydrate found in foods.

In 1894, Atwater’s nutritional guide became the first published by the United States Department of Agriculture. Hammering the economic point, it was filled with price calculations for various foods factored with the calories they provided. A section titled “Cheap vs. Dear Food” compared the “calories of energy” available from, say, 25 cents’ worth of oysters with 25 cents’ worth of wheat flour (news flash: the flour was less “dear”). This little-known economic aspect of the calorie likely reached its apex in 1920, when former Michigan Governor Chase Osborn proposed that international trade should use the calorie rather than precious metals as a universal currency: The value of an item, he proposed, would be based on the calories required to produce it. For example, the cost of a wool coat would depend on the calories needed to raise the sheep, shear the wool, sew the garment, transport it to market and so on. Unwieldy to say the least.

The Progressive ideals of the age, which fixated on science, rationality and quantification, were pervasive, and the nascent food-marketing industry saw a possible bonanza. As early as 1915, the Joseph Schlitz Brewing Company seized upon the calorie. “Pure Beer Is Next to Milk as Energy Builder,” Schlitz proclaimed in a newspaper ad. “A glass of milk yields 184 calories; a similar glass of pure beer, 137 … And Doesn’t Make You Bilious.” An ad for Presto Quick-Flour compared a pound of prime beef with a pound of its flour—1,000 calories versus 1,600 calories—and their respective prices, 25 cents versus 6 cents. “Presto is thus proven four times as good value as beef—just ponder on that!”

The excitement was also filtering into academia. When Peters was earning her medical degree, she likely would have studied Atwater’s writings and his calorie guides as a tool in determining children’s nutritional needs, one of her areas of expertise. (Atwater died in 1907, while she was still in medical school.) But her novel insight was to look at the calorie the other way around, by hypothesizing that it might be used not only to guide healthy weight gain but weight loss as well. “Peters was part of a movement of food reformers in this time period who were turning toward making food more rational,” says Helen Zoe Veit, a food historian at Michigan State University and the author of Modern Food, Moral Food: Self-Control, Science and the Rise of Modern American Eating in the Early 20th Century. “The idea was to eat, not because of tradition or god forbid for pleasure, but according to science and numbers, and to the new knowledge about nutrition.”

Having struggled with what she felt was her own excess weight, Peters made her body her first research subject, and she interpreted her 70-pound loss as a resounding mandate.

Peters was a savvy promoter, but she was also lucky. The decade in which she launched her calorie crusade was uniquely suited to her skills as a communicator—and to her message. A tsunami of social transformations had been building from the turn of the century, including a shifting cultural preference from the curvy Gibson Girl of the 1890s to a whittled-down, boyish silhouette that would become the 1920s flapper. Through the second half of the 19th century a certain plumpness, especially in women, had been seen as charming, healthy and feminine. It also served as a signal of wealth and abundance. As the 20th century began, however, excess weight came to be associated with the lower classes and the poor, while slenderness became counterintuitively a sign of affluence and status.

To explain the shift, many historians point to the ideas of the American economist and social scientist Thorstein Veblen, presented in his 1899 book, The Theory of the Leisure Class. The new upper-middle class that arose in the wake of the Industrial Revolution, he posited, displayed not only “conspicuous consumption” but also “conspicuous waste.” And what said “waste” better than being food-secure enough to turn away food? A starving person would never diet, but a debutante could if it meant slipping into a form-fitting ball gown.

Newspaper Article — In addition to her *Diet and Health* book, Peters penned a daily newspaper column with the same title, often responding to readers’ letters by sharing her own weight-loss struggles. Newspapers.com

That shift is illustrated in a study of dieting among women at Smith College, published in the Journal of Women’s History in 1995, which documented how body weight was seen between the 1890s and 1920s. In the earlier years, students wrote home about the wonderful feasts they enjoyed at school, and even about their goals to gain weight. A student weighing 135 pounds wrote to her mother in February 1892: “It is my ambition to weigh 150 pounds.” Educators and social pontificators had fretted that academic life would take a toll on young women’s health and, importantly, their feminine appeal and future reproductive capacity. Packing on a few pounds, rather than wasting away, was seen as proof of robustness.

By the early 1920s the script had flipped. Dieting culture became so pervasive that a letter to the editor published in the Smith College Weekly in 1924 was titled “To Diet or Not to Die Yet?” Written by three Smith students, the letter warned against the obsession with weight loss: “If preventive measures against strenuous dieting are not taken soon, Smith College will become notorious, not for the sylph-like forms but for the haggard faces and dull, listless eyes of her students.”

Fashion followed a similar trajectory. Nineteenth-century designs had exaggerated female-specific roundness, first with hoop skirts and later with bustles, although the generous bottom halves were balanced out by a nipped-in waist, courtesy of corsets. But by the late Victorian era, doctors were railing against the garment, and what was coined the corset controversy arose. Almost a century before the so-called bra-burning movement in the late 1960s, early feminist Elizabeth Stuart Phelps Ward wrote, in 1873, “Burn up the corsets! … Make a bonfire of the cruel steel that has lorded it over the contents of the abdomen and thorax so many thoughtless years, and heave a sigh of relief; for your ‘emancipation,’ I assure you, has from this moment begun.”

Fashion finally began to loosen its hold on the corset in the first decade of the 20th century, only to usher in the hobble skirt—a straight, narrow silhouette that replaced the nipped-in waist with a hem so tapered that the wearer’s legs could barely move. Fashion designer Paul Poiret, the hobble skirt’s inventor, wrote of this era in his 1931 autobiography, “It was in the name of Liberty that I proclaimed the fall of the corset,” while adding that though he “freed” the bust, “I shackled the legs.”

After World War I ended, Peters (front row, center with glasses) traveled to Serbia with fellow women doctors and dentists on a Red Cross humanitarian mission to deliver food and treat disease. Tango Images / Alamy

The irony was that while women were giving up the torments of corsets and hobbles, they substituted a form of internal torture to control their bodies: what became known as “reducing.” To that end, they were aided by another innovation: the bathroom scale, which appeared on the American market in 1913. Until then, people had their weight measured only at doctors’ offices, or at public “penny-slot” scales found in movie theaters and department-store restrooms. When medical advances like sanitation systems, vaccination and pasteurization presented the promise of better hygiene and longer life spans, people began to feel that their health was in their own hands. A personal scale, like the calorie, offered would-be reducers a magic number, a way to quantify their success, or failure, and a sense of control over the process of reducing—or, as Peters came to call it, “Petersizing.”

Into this newly weight-conscious landscape stepped Peters. She began her book by being daringly honest about her frustrations with her weight, even as many other details of her life remained in shadow. We know that Peters was born to Thomas and Alice Hunt in 1873 and reared in the small town of Milford, Maine. She attended Eastern Maine State Normal School and then moved to California, where she married Louis H. Peters in 1899. Several years later, she began her medical training.

Louis Peters plays nary a role in the history books, and he rarely appears in Lulu’s writings. What did he make of her growing fame—and of her hard-won smaller silhouette? Was part of her impetus to lose weight a desire to please her husband? On the contrary: In her book, Peters wrote that once you start reducing, you will have to combat “your husband, who tells you that he does not like thin women. I almost hate my husband when I think how long he kept me under that delusion. Now, of course, I know all about his jealous disposition.” She also mentions that she was near her heaviest when the two married, so presumably her plumpness was not a deal-breaker.

Veit, the food historian, cautions against drawing conclusions about Peters’ marriage. “She does make sure to establish that she is married, because that would be a sign of status,” Veit says. “For a single, middle-aged woman—what was then called an ‘old maid’—to write a book like this would have been a mark against her. So she makes clear at the outset, ‘I have been successful on the marriage market.’” Other writers of weight-loss narratives in the 1920s, who were enjoying their first boom thanks to both Peters and the new flapper ideal, were also explicit about slenderness being “part of maintaining the chemistry in your marriage,” Veit adds. “At that time, attractiveness was being more and more linked to a certain kind of figure.”

Corset Flapper — In the early 1900s, fashion trends evolved from tight-fitting and often uncomfortable corsets that exaggerated women’s curves to looser flapper dresses that created narrow, almost boyish silhouettes. Left: Smithsonian Libraries, American History Trade Literature Collection; Right: GraphicaArtis / Getty

In a presage of a confessional media environment still far in the future, Peters’ struggles with weight were part of her public persona—and, as with Oprah Winfrey and Weight Watchers founder Jean Nidetch, key to her business pitch. Of her pudgy childhood and relentless weight gain, she wrote, “I never will tell you how much I have weighed, I am so thoroughly ashamed of it,” only to add “but my normal weight is 150 pounds, and at one time there was 70 pounds more of me than there is now.” The use of the word “ashamed” to describe her 220 pounds was no accident. Peters believed that shame was a strong motivator, a notion that comes up repeatedly in her works. (She later wrote a newspaper column titled “A Disgrace to Be Fat.”)

Today we would call this language fat-shaming and recoil at the words, says Chin Jou, an interdisciplinary food historian at the University of Texas at San Antonio and the author of Supersizing Urban America: How Inner Cities Got Fast Food With Government Help. And yet, while we may not use such blunt language, Jou says, Peters’ “underlying fatphobia is still very much a part of dominant American ideas about what constitutes a healthy and aesthetically pleasing body.” As for the word “fat,” she continues, today’s self-described “fat acceptance” activists and advocates are trying to reclaim it by untangling it from ideas about morality and self-control.

For Peters and others in her time, though, the supposed immorality of plumpness was intimately bound to her message. She compared keeping up dieting to keeping up “other things in life that make it worth living—being neat, being kind, being tender; reading, studying, loving.” Veit says, “Being fit was seen as the visible expression of moral issues—having to do with self-control, being smart, ambitious, efficient. All of these virtues from the era were tied up with not eating too much.” Moreover, Veit goes on, “She felt that she was speaking with authority: ‘I’ve done it so you can, too.’ And that gave her license to be really outwardly, explicitly bigoted against fat people. Today, it’s become socially unacceptable to say that fatness results from personal failings, but there remains a tremendous amount of moralization of thinness and fatness that’s part of mainstream culture.”

Peters, ever the intuitive marketer, also linked what she saw as the inherent morality of slenderness to another high-profile virtue: patriotism. When the United States entered World War I in 1917, the federal government promoted cutting back on consumption with the catchphrase “Food Will Win the War.” Colorful cookbooks and posters extolled flourless “victory meals” and “sowing the seeds of victory” by growing your own vegetables (“Every Garden a Munition Plant!”). One leaflet explained the value of self-sacrifice more explicitly. “Sugar Means Ships: The sugar used in sweet drinks must be brought to America in ships. … These ships must now be used to carry soldiers to the front. Drink less sweetened beverages. We are at war. Every Spoonful—Every Sip—Means less for a Fighter.”

Save a loaf Poster — The U.S. Food Administration urged Americans to cut back on sugar, wheat, fats and meat during World War I. © 2024 Museum of Fine Arts, Boston. All rights reserved. / Gift of John T. Spaulding / Bridgeman Images

Peters put her own spin on the calories-patriotism equation. Barely four paragraphs into Diet and Health, she wrote, “In wartime it is a crime to hoard food. … Now fat individuals have always been considered a joke, but you are a joke no longer. Instead of being looked upon with friendly tolerance and amusement, you are now viewed with distrust, suspicion and even aversion! How dare you hoard fat when our nation needs it? You don’t dare to any longer.”

Peters advised rounding up one’s overweight friends and forming a Watch Your Weight Anti-Kaiser Class. The class should invest in a good accurate scale, she explained, and meet once a week to weigh themselves—an idea (minus the kaiser element) that found new life in the early 1960s when Nidetch launched the neighborhood weight-loss clubs that would become Weight Watchers. To her credit, Peters put her own boots on the ground in Europe after the armistice. In 1919, she joined a Red Cross medical delegation to the Balkans and stayed there for almost two years, earning decorations from the Serbian and Albanian governments for her child welfare and public health work amid the devastated postwar civilian population. Peters later wrote about “medical calls on foot in the scorching sun over unkind cobblestones, long-distance calls on unkinder mules, long hours in nerve-racking clinics [and] ferocious man-eating mosquitoes.”

She returned home in 1921 to find her book going into multiple editions, and on April 25, 1922, she debuted a daily “Diet and Health” column in the Los Angeles Times, which propelled the book to the best-seller lists. The column would ultimately be syndicated to newspapers nationwide and continue until her untimely death, from pneumonia, in 1930.

From the start, Peters’ column put her talents as a sprightly and engaging writer on display. She addressed the reader as a friend whose struggles she understood. She was also shrewd, in a surprisingly modern way, about the power of the come-on—and the cliffhanger. Titled “What’s Your Weight?,” that first column walked readers through the various ills, such as diabetes, that could be attributed to excess weight, before ending with: “Do you want to reduce? Foolish question number 13,579. Why, you want to reduce more than you want anything on the face of the globe or the feet of the gods! We’re going to show you how. Tomorrow’s the day. And it’s oh, so simple!”

The simplicity was the draw, in the same way that modern-day diets promise “easy” weight loss. What also likely kept readers coming, though, was Peters’ frankness, her willingness to get into the trenches with other “fat friends.” One week into her column’s run, she wrote an entry titled “My Most Embarrassing Moment.” In it, she described an incident when she was about 50 pounds overweight, and she stepped into an elevator. “No one got out, and I got in,” she wrote. “The operator shut the door and pushed the lever of the car. No response. Back and forth he pushed. … Car did not quiver.” A “gracious gentleman” got out; the car didn’t budge. Another gentleman followed, to no avail. “Blushing, but game, I said with a wan smile that I would get out. The car shot up”—but not fast enough for her to miss the “imbecilic laughter” of those inside. It was “embarrassing,” she admitted, but also “invaluable. … I reduced.”

Victory Meals Poster — The resulting “victory meals” left more supplies available to feed both members of the military and starving civilians in Europe. Tango Images / Alamy Stock Photo

Peters urged her readers to “send in your most embarrassing moment!” in the style of a modern-day master of social media soliciting likes and comments. And it worked: Eventually she was receiving thousands of letters, which she often used as material in her columns. To “Mary,” who wrote to Peters saying how much she was encouraged by her personal story of weight loss, she replied at confessional length. “It’s a continuous fight, Mary! … I find that if I get started on candy nuts, I’m just like a drunkard with his dram. … It was only last week that I had my last gorge. I had had a good dinner, but I had a longing for those pernicious candied nuts. I bought a pound, and I’ll be darned if I didn’t eat the most of them myself. … When I averaged my calories for that day, they mounted to nearly 4,000, almost enough to keep me going for three days!”

Peters was a product of her times, with flapper-style bobbed hair, fringed headbands and plucked eyebrows, but she was also a harbinger of the future. Many modern marketing ploys echo Peters’ methods—for instance, the fixation on 100-calorie portions. Peters organized her “key to the calories” by units of 100 calories: For that number, you could have one and two-thirds ounces of chicken, three ounces of lean fish or one average-size apple. Today, a vast array of snack items, from pretzels to mini-protein bars, are offered in 100-calorie packages. And Peters’ instructions are familiar to any contemporary dieter: “You may be hungry at first, but you will soon become accustomed to the change,” she wrote. Elsewhere, a warning: “Don’t ‘taste’! You will find the second taste much harder to resist than the first.”

Generations of Americans have adopted Peters’ idea to count calories, encouraged by a public health infrastructure that instructs us to “eat less and move more.” Unfortunately, the fruits of this advice have been dismal. The vast majority of calorie-restricting diets have been shown to fail in the long run and in fact often result in a weight regain beyond the starting weight. Numerous studies over recent decades have shown that taking in calories and burning them (that is, eating and exercising) are not separate processes but are instead intimately related in a complex dance: Cutting calories triggers a cascade of hormonal reactions that increase hunger and fatigue while slowing metabolism, making it more difficult to lose weight. One research analysis in the journal Public Health Nutrition describes attempts to achieve and maintain a calorie deficit as “practically and biologically implausible.” New weight-loss drugs such as Ozempic appear to interrupt that cascade, by manipulating hormones in the gut and the brain to decrease appetite.

Peters’ focus on units of 100 calories still influences today’s food industry. Snacks of all stripes strive to project a healthful aura by touting their calorie counts and designing serving sizes that hit that magic number. Karen Warren / Houston Chronicle via Getty

Meanwhile, the latest figures from the Centers for Disease Control and Prevention show that 42 percent of American adults are obese, compared with 30 percent just 20 years ago. (In 1962, it was 13.4 percent.) As these numbers rise, along with rates of Type 2 diabetes, the edifice that Peters—and Atwater, in his own way—constructed around the calorie has begun to crumble. Increasing amounts of research suggest that the mathematical equations they promoted are drastic over-simplifications. Consider Peters’ calculations, outlined in her book: “Cutting out 1,000 calories per day would equal a reduction of approximately 8 pounds per month, or 96 pounds per year.” Under this logic, one could continue to shrink away to nothing by simply continuing to cut out 1,000 calories per day, but it doesn’t work that way. Peters herself discovered the limits of her body’s ability to shed pounds. She longed to break through her own plateau and dip down closer to 150 pounds, but despite a draconian regimen limiting her to about 1,200 calories per day plus regular exercise, she never succeeded.

The error in the “calories in-calories out” equation may boil down to this: Human bodies are not coal-burning machines, and food is not coal. Rather, the body and food are both vastly more complex, and they interact in complicated ways that have evolved in humans over eons. Researchers are finding that body weight and virtually everything that influences it—hunger, satiety, metabolism, fat storage—are affected by a broad range of factors that were a mystery 100 years ago. These include hormones, such as insulin, which increases appetite and promotes fat storage; ghrelin, the “hunger hormone”; and leptin and peptide YY, which are called “satiety hormones.” We are also still learning about the microbiome—the unique population of bacteria in an individual’s digestive tract—and how specific bacteria can powerfully affect weight loss or gain, as well as mechanisms like the parasympathetic nervous system, which can affect energy expenditure (the “calories out” part of the equation).

Numerous factors inherent in foods affect how many calories are actually retained in the body, and whether those calories are stored as fat or, for instance, burned for energy or used to build tissue and muscle. Highly processed carbohydrates break down almost instantly in the body, prompting insulin release and fat storage; protein breaks down slowly and requires more energy to do so, essentially “using up” some of its calories just in digestion. Some foods, including certain types of nuts, have considerably fewer calories when measured in the body than they have in lab tests. And food when raw yields fewer calories in digestion than the same food cooked. These anomalies are just the tip of the iceberg.

Ozempic and similar drugs, first prescribed to regulate diabetes, have reshaped the debate around losing weight through will-
power alone. George Frey/Bloomberg via Getty Images

No surprise, then, that a 2013 book titled Why Calories Count faces off against another from 2021 titled Why Calories Don’t Count, and that nutritional conferences have become hotbeds of argument and contention. Some experts on the anti-calorie-counting side believe that, beyond being a disappointment for generations of dieters, calorie-reduction regimens and their promoters bear some responsibility for the obesity epidemic. Jason Fung, a nephrologist and expert in obesity and Type 2 diabetes, writes in his book The Obesity Code that calorie reduction is a “cruel hoax.” By prioritizing calories over other considerations, such as macronutrient makeup (proportions of carbs, fats and protein) and the effects of industrial processing, the “just cut calories” theory fostered the idea, he writes, that “100 calories of cola is just as likely as 100 calories of broccoli to make you fat.” Making calories the kingpin also helped lead to the low-fat-diet movement, which Fung and other experts blame for ushering in our current age of obesity. The medical establishment decades ago prescribed reducing fat intake in favor of moderate protein and plentiful complex carbs. In practice, that advice seemed to give many people license to load up on simple, processed carbs in place of satiating fats. That in turn leads to more insulin release, in order to move sugar out of the bloodstream and into storage—which leads to more hunger, more snacking and bigger fat stores on the body.

There are signs that the “calories aren’t everything” message may be seeping into the public consciousness, but many of Peters’ talking points about obesity and weight loss still linger: for one, the obsession with quantification. While fewer people may be counting calories, Veit says, “Whether it’s our weight, our BMI, clothes size, life expectancy, cholesterol levels, there are all these other numbers we associate with our bodies.” Not to mention replacing counting calories with counting carb grams, as some are now doing. And while the overt fat-shaming of Peters’ era is now more frowned upon, striving for slenderness seems to retain a moral dimension. In some ways, says Jou, “Feminine diet culture today can be even more taxing on women. Not only do participants of diet culture manage their food intake, but they also tend to undertake considerable exercise regimes to achieve a ‘toned’ look. The women following Peters’ diet program were just trying to be thin.”

Today’s strivers may talk about eating “clean” and improving their health, but the ideal baseline is still to be lean, and those who are heavy frequently continue to be quietly judged and found lacking in simple willpower. Will new drugs like Ozempic, which demonstrate the biological underpinnings of obesity, begin to lift that blame? Possibly. But for many people, there appears to be an inherent logic to the idea of simply buckling down and cutting back.

Decades later, Peters’ belief in willpower over want still resonates. “Your stomach must be disciplined,” she wrote in 1918.

What could be simpler?