100 years of fad diets: Experts weigh in

Anna Hoychuk // Shutterstock Diet trends have come and gone over the years. Some were quirky, while others had dangerous restrictions.  Who hasn’t heard of a celebrity-backed liquid cleanse or the promise of rapid weight loss after adhering to strange food combinations? But which of these fads actually worked, and which do nutrition experts in 2025 firmly discredit?  To help kickstart your New Year’s health goals, MyFitnessPal dietitians took a deep dive into the evolving history of fad diets to see if any had merit. They also provided evidence-based recommendations for building a sustainable, healthy lifestyle.  Here’s a decade-by-decade breakdown of the most iconic diet fads over the past 100 years and their impact on health, according to experts. 1920s-1930s: The Grapefruit Diet  The trend  Also known as the “Hollywood Diet,” this popular approach involved eating half a grapefruit before every meal. The claim? Grapefruit contained enzymes that could “burn fat,” turning the fruit into a shortcut for weight loss.  RD verdict  “Adding fruit to your diet can actually be a great way to help with weight loss! It adds fiber to help you feel full. It’s typically low in calories but high in volume,” says Stephanie Nelson, MyFitnessPal’s Senior Lead Nutrition Scientist.  But she emphasizes that grapefruit does not burn fat.  Adding grapefruit to meals “without making any other changes to your diet won’t actually result in weight loss,” says Nelson.  Melissa Jaeger, RD, LD, Head of Nutrition at MyFitnessPal, agrees. She notes that grapefruit has a variety of vitamins and minerals, like vitamin C, which support immune systems.  “But there simply isn’t any scientific evidence to support fat-burning claims about grapefruit,” she concludes. Jaeger also notes that some versions of this diet limited daily calories to 800. That is not enough to meet daily energy needs. She also warned that grapefruit and its juice interact with some medications. So, this diet may be risky for some people. Always talk to your doctor about foods you may need to avoid if you take medications.  Expert takeaway  Enjoy grapefruit as part of a balanced diet, but forget the fat-burning claims. Healthy, sustainable weight loss requires a reasonable calorie deficit and a focus on nutrient-rich foods. 1940s-1950s: The Master Cleanse  The trend  Trending in the 1940s and popular again in the early 2000s, The Master Cleanse, also known as the Lemonade Diet, involved a mostly liquid diet regimen.  During the main cleanse phase, dieters drank a mix of lemon juice, maple syrup, cayenne pepper, and water for several days. They aimed to “detox” and lose weight.  They also drank a cup of laxative tea in the evening to encourage bowel movements.  RD verdict  “Juice cleanses cause weight loss because people who try this essentially starve themselves,” says Nelson.    Notably, much of the weight lost during cleanses is likely due to the loss of water and muscle mass rather than actual body fat.  She adds that “people who try this approach tend to gain the weight back after the ‘cleanse’ is over unless they change their diet habits long-term.” Nelson explains that people must change their diet to lose weight long term, so this cleanse is ineffective. Expert takeaway  A liquid cleanse isn’t necessary, and doing one may lower metabolism. The body already has effective built-in detox systems–the liver and kidneys. Taking laxatives when you don’t need them can also lead to complications like dehydration, as you lose fluid in your stools.   Overall, Nelson advises, “It’s best to skip this one!”  1960s: The Sleeping Beauty Diet  The trend  The most extreme version of this diet advised dieters to sedate themselves for up to 20 hours a day. This was to avoid eating entirely during those hours.  RD verdict  This is a very dangerous diet trend, cautions Emily Sullivan, RD, Food Data curator at MyFitnessPal.  Among serious health complications, she warns that this diet could lead to malnutrition from not eating enough, along with risk of addiction to sleeping pills. Instead, Sullivan advises getting the right amount of sleep, which is crucial for weight management and overall health. She suggests that seven to nine hours of sleep per day is ideal, and in fact, some research shows that sleeping less than six hours per night can lead to weight gain.  On the other hand, she notes that oversleeping, such as nine to ten hours nightly, has also been linked to weight gain when compared to sleeping seven to eight hours. Expert takeaway  Prioritize quality sleep, but stick to the recommended daily range. Oversleeping or using sedatives to avoid eating has no place in a healthy lifestyle. If you have disordered eating or trouble sleeping, reach out to a doctor or mental health professional for support. 1970s: The Egg & Wine Diet The trend  This three-day diet involved eating eggs, black coffee, and wine for breakfast and lunch. Then, steak and wine for dinner.  The idea was to reduce calorie intake drastically but make dieting more “tolerable” by including alcohol.  RD verdict  Jaeger says, “This diet is low in nutrient-dense calories with a high concentration of calories from alcohol–not the makings of a safe, balanced, nutrient-rich diet.” She notes that it lacks fruits, vegetables, whole grains, and healthy fats. So following this diet for a long time may risk nutritional deficiencies due to its extreme restrictions. Also, the diet’s reliance on alcohol raises health concerns, from dehydration to impaired judgment. Alcohol has empty calories and promotes inflammation. This negatively impacts health and weight goals. Overall, Jaeger says that “quick fixes” and very restrictive diets don’t lead to safe, effective weight loss or healthy habits. Expert takeaway  This diet reflects the worst of quick-fix fads. It’s restrictive, promotes harmful drinking behaviors, and does nothing for long-term health or sustainability. 1980s: The Cabbage Soup Diet