Dieting as a mainstream cultural practice took root in the early 20th century, but it didn’t become a mass phenomenon until the 1920s. That’s when calorie counting entered the public vocabulary for the first time, thanks to a bestselling book and shifting beauty standards that prized slimness over the fuller figures admired in previous decades. From there, dieting evolved through distinct eras, each shaped by new science, government policy, and commercial opportunity, growing into a global industry now valued at roughly $177 billion.
The 1920s: Calorie Counting Goes Mainstream
Before the 20th century, being heavy was often a sign of prosperity. That began to change after World War I, when American physician Lulu Hunt Peters published Diet & Health: With Key to the Calories in 1918. It became the first weight-loss book to reach bestseller status and introduced everyday readers to the idea that food could be measured in caloric units and managed like a budget. Peters had already built a following through her newspaper column of the same name, and her advice reframed eating as a matter of personal arithmetic rather than simply choosing different foods.
The timing mattered. The 1920s brought new ideals of femininity: the slim, athletic “flapper” silhouette replaced the corseted, curvier look of the Victorian and Edwardian eras. For the first time, large numbers of otherwise healthy people began restricting what they ate purely to change their appearance. Dieting shifted from a medical intervention for the visibly ill to a lifestyle choice for the general public.
The 1940s: Insurance Companies Define “Ideal” Weight
Dieting got an institutional backbone in the early 1940s, when the Metropolitan Life Insurance Company published its first height-and-weight tables. The 1941 table covered men, the 1942 table covered women, and both sorted “ideal” weights by height and three frame sizes: small, medium, and large. These numbers were drawn from the weights of insured people aged 20 to 29, and the tables stated that weight should remain unchanged throughout adult life, with no allowance for gaining weight as you aged.
Metropolitan Life updated these tables in 1959 with slightly higher recommended weights and narrowed the age range to 25 through 59. No guidance was ever provided for how to determine your own frame size, which made the categories somewhat arbitrary. Still, the tables gave doctors, employers, and millions of ordinary people a concrete number to aim for. If you weighed more than the chart said you should, you were officially “overweight,” and the implication was clear: you needed to diet.
The 1970s: Government Gets Involved
Dieting took on a political dimension in the late 1970s. In 1977, Senator George McGovern’s Select Committee on Nutrition and Human Needs issued a landmark report urging Americans to change what they ate. The committee recommended reducing saturated fat to no more than 10% of daily calories and capping cholesterol at 300 milligrams per day. The report explicitly told people to eat less meat and more poultry and fish.
These recommendations didn’t appear in a vacuum. The American Heart Association had already advised in 1973 that Americans cut total fat to 35% of daily calories and halve their cholesterol intake. But the McGovern report carried the weight of the federal government, and it catalyzed the low-fat era that would dominate American dieting for the next two decades. Food manufacturers responded by flooding supermarket shelves with low-fat and fat-free products, often replacing fat with sugar. An entire generation grew up believing that dietary fat was the primary enemy.
The 1990s and 2000s: Fad Diets Multiply
The Atkins diet, which restricts carbohydrates to as little as 20 grams per day while allowing unlimited protein and fat, was first introduced in the 1960s. For more than 30 years it was ridiculed as dangerous nonsense by mainstream nutrition experts. That changed after the turn of the century, when short-term studies began showing that low-carb diets could initially produce better results than conventional low-calorie, low-fat approaches. The diet’s appeal also came from what it permitted: meat, fish, eggs, and cheese in unlimited quantities felt like freedom compared to the restriction of calorie counting.
The early 2000s low-carb boom was just one wave in a broader explosion of competing diet plans. The Zone, South Beach, paleo, and eventually keto each promised a different framework for the same goal. This era marked the moment dieting became a full-blown identity category. People didn’t just follow a diet; they joined a camp, bought branded foods, and debated the merits of their approach online. The weight management industry grew rapidly as a result.
The BMI Era and a Global Epidemic
In 1997, the World Health Organization formally recognized obesity as a global epidemic. This declaration cemented body mass index as the standard metric for categorizing weight worldwide and intensified public health messaging around weight loss in dozens of countries simultaneously. Dieting was no longer just an American preoccupation. It became a global health priority, backed by government campaigns, school nutrition programs, and workplace wellness initiatives.
CDC survey data shows the steady normalization of dieting in American life. Between 2007 and 2018, the percentage of U.S. adults on a weight-loss or low-calorie diet rose from 7.5% to 10.0%. That may sound modest, but it represents millions of additional people actively restricting their food intake in any given year. And it doesn’t capture the much larger number of people who think about dieting, attempt it briefly, or modify their eating without labeling it a “special diet.”
The 2020s: Prescription Weight Loss
The newest chapter in the history of dieting barely involves food restriction at all. Prescriptions for GLP-1 drugs, sold under brand names like Ozempic and Wegovy, have more than tripled since 2020. These medications, originally developed for type 2 diabetes, reduce appetite by mimicking a gut hormone that signals fullness to the brain. For the first time, millions of people are pursuing weight loss primarily through pharmacology rather than dietary rules.
This shift is reshaping the weight management industry on a massive scale. The global market is projected to grow from roughly $177 billion in 2025 to $392 billion by 2035. Much of that growth is driven by pharmaceutical spending rather than diet books, meal plans, or gym memberships. Whether this represents the end of traditional dieting or simply its latest evolution is still playing out, but the trajectory is clear: what started as calorie arithmetic in a 1918 newspaper column has become one of the largest consumer health markets on the planet.