Diet trends have come and gone over the years. Some were quirky, 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, focused on nutrition for real life.
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.
Dietitian 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 (1).
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 supports our immune systems (2).
“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 (3).
She also warned that grapefruit and its juice interact with some medications (4). 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 (5).
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.
Dietitian Verdict
“Juice cleanses cause weight loss because people who try this essentially starve themselves,” says Nelson (6).
Notably, much of the weight lost during cleanses is likely due to the loss of water and muscle mass rather than actual body fat (7).
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 (6).”
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 your metabolism (8). Your body already has effective built-in detox systems—the liver and kidneys (9, 10)!
Taking laxatives when you don’t need them can also lead to complications like dehydration, as you lose fluid in your stools (11).
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.
Dietitian 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 (12, 13).
Instead, Sullivan advises getting the right amount of sleep, which is crucial for weight management and overall health.
She suggests that 7-9 hours of sleep per day is ideal, and in fact, some research shows that sleeping less than 6 hours per night can lead to weight gain (14).
On the other hand, she notes that oversleeping, such as 9-10 hours nightly, has also been linked to weight gain when compared to sleeping 7-8 hours (15).
Expert Takeaway
Prioritize quality sleep, but stick to the recommended daily range. Over-sleeping 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.
Dietitian 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 (16).
Also, the diet’s reliance on alcohol raises health concerns, from dehydration to impaired judgment (17, 18).
Alcohol has empty calories and promotes inflammation (19, 20). 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
The Trend
This week-long diet allowed unlimited cabbage soup. It paired the soup with modest portions of specific foods, like skim milk or fruit, on certain days. Like many fad diets, it promised rapid weight loss.
Dietitian Verdict
“While recipes found online for making homemade cabbage soup for this diet contain a variety of vegetables, this singular recipe does not make for a balanced diet,” says Jaeger.
This diet is extremely low in calories and lacks protein, fat, and other vital nutrients. Any rapid weight loss is likely mostly water and lean muscle, not fat, and is not a long-term solution (7).
Jaeger also emphasizes that this diet does not have scientific evidence to support its weight loss claims or to review its safety.
She advises us to build sustainable diets, avoiding fads that claim to help us rapidly meet our goals.
Expert Takeaway
Aim for variety in your diet rather than focusing on one food or type of meal. Addressing entire eating patterns makes sustainable weight loss more successful.
1990s: The Blood Type Diet
The Trend
This diet claimed a person’s blood type (A, B, AB, or O) dictated which foods were healthiest for them.
For example, type O individuals were advised to eat a high-protein, meat-heavy diet, limiting vegetarian proteins (21). In contrast, type A individuals were encouraged to avoid meat and instead choose more seafood and vegetarian protein sources (21).
Dietitian Verdict
“The concept behind these diets is that an individual’s blood type is theorized to be their ancestral blood group,” says Brookell White, MS, RD, a Food Data Curator at MyFitnessPal.
Though the idea of this diet appealed to many, there is a lack of research to support its claims.
One study of this eating style found potential benefits for body weight and some health markers, like blood pressure and cholesterol (22).
But White points out that the health benefits in followers were likely due to better eating habits (more vegetarian foods) rather than blood type (22).
“This seems to be the consensus for most studies that have been done,” she says (23, 22).
Expert Takeaway
There’s no need to determine your blood type to eat healthfully. Focus on evidence-based dietary patterns with plenty of variety, such as the Mediterranean diet.
2000s: The Raw Food Diet
The Trend
One of the more lasting trends, the Raw Food Diet, promotes eating uncooked, unprocessed foods to retain natural nutrients and enzymes. Usually, people following a raw food diet only eat vegan, plant-based foods.
Dietitian Verdict
Daisy Mercer, RD, a Food Data Curator at MyFitnessPal says eating raw foods like fruits and vegetables can have benefits. These foods provide important nutrients like fiber, antioxidants, vitamins, and minerals (24).
Mercer also says that eating raw often means eating less processed food. It will generally provide us with more fiber, and our bodies will work harder to digest them. That will lead to better satiety and less desire to overeat.
Eating a raw food diet may also help reduce intake of sodium and saturated fats, she notes.
Additionally, raw plant-based foods may contain more vitamins and minerals (25). Some nutrients can be lost in cooking, Mercer points out (25).
For example, certain cooking methods, like boiling, can greatly reduce the water-soluble vitamin content, like vitamin C, in fruits and vegetables (26). It may be best to cook high-vitamin C foods more quickly, with less heat and water, such as by steaming (26).
But research suggests that a mix of raw and cooked foods in the diet may be best for our health (25).
A raw vegan diet, with over 90% raw foods, might not be safe long-term (25). It may cause micronutrient deficiencies and other health issues (25).
Mercer cautioned that a raw food diet can also become dangerous when raw or undercooked meats are involved, posing a risk of foodborne illness (27).
Expert Takeaway
Eating more fruits and vegetables is a great way to support your health. Instead of worrying about whether they’re cooked or raw, focus on eating a variety of plant-based foods as part of a balanced diet.
2010s: Juice Cleanses
The Trend
Juice cleanses are when you consume nothing but juice from fruits and vegetables for a period of time, often from one day to one week. It became trendy as a “detox” method, with supporters claiming it “resets” the body.
Dietitian Verdict
Like any liquid fad diet, juice cleanses can cause rapid weight loss (28).
“This is mostly due to not consuming enough calories,” Mercer points out, rather than any special effect of the juice cleanse on weight loss (28).
And, once again, if you don’t make healthy, sustainable changes to your diet, you’ll likely gain the weight right back (28).
Mercer notes that drinking unsweetened, 100% fruit and vegetable juices in moderation can boost your vitamin and mineral intake (29).
Just keep in mind that juice lacks fiber. This leads to quick absorption of natural sugars, which can act like refined sugar and cause short-term blood sugar spikes (30).
Additionally, we often consume more juice than we would whole foods, resulting in extra calories (31).
Juices with lower natural sugars and calories, like celery or cucumber juice, may be better for managing body weight.
Expert Takeaway
Unsweetened fruit and vegetable juices can be part of a balanced diet in small amounts. Just don’t rely on them for nutrition or unnecessary “cleansing” of the body. For healthy weight loss, choose whole fruits and veggies most often, and use juice splashes to flavor your water!
2020s: The Carnivore Diet
The Trend
This diet promotes eating like some early ancestors who only consumed animal products, including meat, eggs, and some dairy. It aims for weight loss and claims to have anti-inflammatory effects.
Dietitian Verdict
Proponents of this diet claim it improves ailments and aids in weight loss, says White.
But, she adds, “there isn’t any evidence that suggests this is true. In fact, evidence seems to suggest that a varied diet is best in most cases (32).”
She warns that the Carnivore Diet lacks fiber and key vitamins, especially C and E.
These nutrients are found almost only in plants (33, 34). They are crucial for everything from gut health to immunity and cancer prevention, she says (35, 36, 37).
Plus, White says that “animal products are high in saturated fat, which may increase your risk of heart disease (38).”
“Red and processed meats are another concern,” she says, noting that the International Agency for Research on Cancer considers processed meats carcinogenic (cancer-causing) and red meats ‘probably carcinogenic’ (39).”
Expert Takeaway
While the carnivore diet may lead to weight loss, it’s restrictive and lacks essential nutrients and scientific support. For the best long-term health and weight outcomes, stick with a balanced diet rich in plant-based foods.
How to Approach “Fad Diets” of the Future (Spoiler: Don’t)
Looking back at 100 years of dieting fads, one thing is clear—the most sustainable weight loss strategies don’t cut corners or rely on “miracle” solutions.
Rather, they promote nutrient-rich, balanced eating combined with exercise and other healthy habits.
“We encourage striving for progress, not the concept of perfection,” says Jaeger.
So, she advises, instead of trying the latest fad or revisiting an old trend, try:
- Tracking your foods
- Building awareness of your nutrition habits
- Know where you stand with your health
And Jaeger concludes, “most importantly, don’t let any diet get in the way of real life.”
“You can choose to enjoy a side of fries when dining out with friends or have a slice of cake at a birthday party, and skip the food guilt,” she says.
Studies show that people who track their food are more likely to achieve their weight goals.
MyFitnessPal empowers you with nutrition knowledge that you need to succeed.
The post 100 Years of Fad Diets: Experts Weigh In appeared first on MyFitnessPal Blog.
