Indeed, the weight-loss fads of past centuries include precedents for all the main contemporary diets, from low-fat, low-calorie ones to high-fat, low- carbohydrate ones, like the Atkins diet. In , a French lawyer, Jean Anthelme Brillat-Savarin, wrote a famous treatise, "The Physiology of Taste," in which he contended that true carnivores and her- bivores did not get fat; it was only when one ingested grain---read: bread---that the trouble started. Around the same time, an American Presbyterian minis- ter, Sylvester Graham, reasoned that, as gluttony was the greatest sin, abstinence must lead to virtue; he advised eating vegetables and drinking water, eschew- ing meat, co ee, spices, and alcohol. For a while, students and faculty at Ober- lin College were made to follow Gra- ham's diet; graham crackers were so named in order to appeal to his aco- lytes. Several years later, Horace Fletcher, known as "the great masticator," touted very slow chewing as the remedy for obesity; adherents included normally skeptical people like Upton Sinclair and John D. Rockefeller. A genuine advance, which put nu- trition on a solid scientific footing for the first time, was the work of the chem- ist Wilbur Atwater. In the eighteen- nineties, he began studying how the body converted food to energy, by plac- ing subjects in a closed chamber and measuring the amount of carbon diox- ide they produced and oxygen they con- sumed after eating various foods. At- water came up with the idea of the food calorie, adapting a measurement previ- ously used for heat energy. In , Her- bert Hoover, then the head of the U.S. Food Administration, worked to pub- licize Atwater's findings. "I eat as little as I can to get going," he said. Low- calorie foods and skipping meals be- came popular. The importance of calo- ries---if energy gained exceeds output, the excess becomes fat---remains one of the few unchallengeable facts in the field of dietary science. Still, further research has shown that calories eaten are only part of what determines weight. Our metabolism reflects an interplay of things like genes, hormones, and the bacteria that populate the gut, so how much en- ergy we absorb from what we eat var- ies from person to person. In the nineteen-fifties, the Ameri- can Medical Association identified obe- sity as the country's No. health prob- lem, and the diet industry exploded.The end of that decade brought the idea of the liquid diet---skimmed milk, supple- mented with bananas or other fruit--- which, in turn, eventually gave rise to products like Metrecal, Carnation Slen- der, and SlimFast. Self-help groups mod- elled on Alcoholics Anonymous began proliferating with the establishment, in , of a movement called (the acronym stood for "take o pounds sen- sibly"). Overeaters Anonymous followed, in ; Weight Watchers, in ; and Jenny Craig, in . The immediate postwar years also brought the first sustained scientific assault on dietary fat. Ancel Keys, a physiologist at the University of Min- nesota, who had spent the war develop- ing nutritionally optimal Army rations and studying the e ects of starvation, became interested in the high rates of heart attack among a seemingly well- fed sector of the population---Ameri- can businessmen. He soon became con- vinced that the saturated fats found in meat and dairy products were the cause, and thus began the war on fat that galvanized my parents. Keys be- came, with his wife, Margaret, an ad- vocate for the Mediterranean diet of unsaturated fats. Their books promot- ing the diet were best-sellers, and Keys, who spent his latter years in Italy, lived to the age of a hundred. (Margaret lived to ninety-seven.) T "The Case Against Sugar,"Gary Taubes, gained prom- inence as a science writer in , with a cover story in the Times Maga- zine---"What If It's All Been a Big Fat Lie?"---which challenged the or- thodoxy of restricting dietary fat. Car- bohydrates were the real danger, he wrote---not just processed foods con- taining refined sugars like sucrose and fructose but also easily digestible starches from grains and vegetables. He expanded these arguments in a book, "Good Calories, Bad Calories" ( ), and, in his new book, he goes much further. Though he now allows that people can eat some carbohydrates and still live a "relatively" healthy life, he sees sugar as the devil incarnate, doing harm independent of its known Wear a part o history. "The March" Abigail Gray Swartz, February 6, 2017 Multiple styles available Shop now at newyorker.modthread.com A percentage o sales will go to the Committee to Protect Journalists* * Three per cent of the purchase price of each shirt sold will be donated to the Committee to Protect Journalists. (Not applicable to sales in AL, HI, IL, MA, MS, and SC.) For more information about the C.P.J. and its work, visit cpj.org.