It is often difficult to define a phrase like “Fad Diet.” For the purposes of this article, we’ll mostly stick with diets that have names or readily understandable parameters. We’ll start with a few basic stats about dieting, but for more information on diet failure statistics and weight-loss statistics, please see those articles.
Quick Hits
Data for certain diets is difficult to come by, as most of it relies on small surveys by publications or studies of individual diets’ success (or failure). Here are some general figures.
- On any given day, 17% of Americans are on what they identify as a “special diet.”
- The four most common types of diet are:
- General low-calorie (9.3% of all adults)
- Diabetic (2.3%)
- Low Carb (2.0%)
- Low fat or low cholesterol (1.8%) [1]
Atkins Diet
Atkins is a diet that stresses the reduction of carbohydrates. There is an “exchange” system, wherein the dieter counts their carbohydrate grams, minus grams of fiber, and attempts to stick to a number based on their weight and weight loss goal.
Diet was created in 1970 by Dr. Robert Atkins. His book two years later kicked off the craze.
Approximately 25% of all people have tried Atkins. [2]
- 37% of those people found Atkins “very effective”
- 46% found it moderately effective
- 11% said it didn’t work much
- 3% said it didn’t work at all.
- That’s an 83% success rate based on the survey.
- In a survey by Health Digest, 16% of people who have tried Atkins “hated it”.
Study Data
What some experts say can be misleading; they are human beings, as well as anyone. But the following comes from not only surveys of professionals, but from study data, as well.
- In a controlled study, participants lost 6.8% body weight.
- May also limit abdominal fat, but increase cholesterol (per studies).
- Separate study showed no significant weight loss after 6 months.
- Yet a third study, however, found 3-4% of people stayed 30% below baseline weight. [3]
- In a study comparing it directly to the Zone, LEARN, and Ornish diets, Atkins participants had significantly better results (-4.7 kg). [4]
- The Professional Opinions: Ranks 21st of 24 diets, but #2 in Fastest Weight Loss. [5]
Keto
Keto, like the Paleolithic diet, is hard for some people to understand. Here are a few basics:
High fat, moderate protein, very low carbohydrate.
- It was invented in 1921 as a cure for epilepsy.
- Gets its name from “ketogenesis,” a metabolic stage brought on by severe reduction in carbohydrates. [6]
- The total “Keto market” is valued at over $1.022 Billion, and is forecast to expand by another $500,000 Million by 2027. [7]
Surveys
The following are brief survey data. These are not collated from any one source, and the largest population surveyed was just over 1,000.
- A team of health experts ranked Keto only 34th out of 35 diets. [8]
- 19% of people surveyed by Yougov have tried the Keto Diet
- 49% found it “very effective”
- 35% found it “somewhat” effective
- 8% said it was ineffective to some degree
- Only 3% said it wasn’t effective at all.
Primary Source Data
The following data were collated by a Keto website. We have individually sourced the original findings to separate the raw numbers from any kind of bias.
- Only 5% of Americans (~12 Million) are currently on a Keto diet. [9]
- Among Canadians (a good American analog for some statistics), only 2% of people on Keto have been on it for 5 years.
More than twice as many Canadians drop Keto as stay on. Reasons given:
- 37% say it is “too strict”
- 34% too expensive
- 24% felt it took “too much time”
- 10% found it too confusing.
- 12% said they saw no results. [10]
- 70% of people chose Keto based on their “own research.”
- Less than 5% say a doctor recommended it.
- 85% of people use the internet for help sticking to the program.
- 55% use cookbooks.
- 65% didn’t change their exercise routine, 27% increased it.
- 45% said that a partner in their house is on the Keto diet, as well.
- 54% said they never/rarely cheated, 41% said sometimes; only 5% said they often break the rules.
- 80% are likely to recommend it, and 94% said they saw positive results.
It’s not surprising that many of these survey data contradict one another. What is consistent, however, is that Keto is not easy, and that the overwhelming majority of people using it find what they deem success.
Paleo
The Paleolithic, or Paleo, Diet is a bit complicated for outsiders to understand. Because it has the most ins and outs, we’ll cover some of its basics first.
- Half of calories must be from lean animal sources.
- 6-12 eggs per week.
- All fruits allowed.
- All non-starch vegetables allowed.
- No coffee, no tea; limited sugar and alcohol.
- 4 oz of nuts per day, and 4 Tbsp of oil.
Entry phase: 3 cheat days, some transitional foods.
Maintenance phase: 2 cheat days, no transitional foods.
Final phase: 1 cheat day/week. [11]
Most of the data on Paleo is based on studies, though they are few and far between. Paleo is still relatively new, and doesn’t have the same decades-long reputation as Atkins and Keto.
- One source says that you can lose between 4 and 6% of total body weight in 10 weeks. [12]
- But it also provides, on average, 50% less calcium than daily requirement.
Self-Reported Data
The Paleo movement is one of the most new, and happens to have an active self-monitoring community. Here are some results from their own survey:
- 91% of Paleo dieters are white.
- 55% are female.
- 77% have a four-year degree or higher.
- Over 50% have a household income of $100,000/year. 10% have an income above $250,000
- Of 1,500 respondents, 250 were no longer Paleo (~16.7%).
- Of them, 40% were on no particular diet.
- 13% were on a generic low-carb diet.
- 10% had gone to Keto
- 3% switched to Mediterranean
- 1% had become vegan/vegetarian [13]
Mediterranean
While for many people this can sound like a loose collection of their favorite foods, while to others it can be confusing given the thousands of miles of coastline in the Mediterranean, this diet actually has a very concise history and set of parameters.
It was designed by the Harvard School of Public Health and two other partner programs based in Europe. The following summarizes the basics:
- Healthy fats, such as olive oil, fish, nuts, and avocado.
- Fish as the predominant protein; red meat once or less per week.
- Water as the main beverage.
- Physical activity via “enjoyable activities.” [14]
The following data are based on research studies; actual results in the general population may vary, though they are also nearly impossible to find or verify.
- Reduces cardiovascular disease by 25%.
- Reduces death by stroke by around 30%.
- Allows for more than 20% more fat intake.
- Helps promote “healthier aging” as defined by cognitive measures and cellular health. [15]
Turning to survey data, based on a poll by Yougov.
- 18% of Americans have said they tried the Mediterranean Diet.
- Of them, 37% said it was “very effective,” and 44% said it was effective.
- 12% said it wasn’t very effective, and only 1% said it was not effective.
Vegetarian
We’ll begin with basic survey data:
According to a Yougov poll, 15% of people have tried Vegetarian diets.
According to
Gallup, however, only 5% of Americans actually identify as Vegetarian.
Back to the Yougov poll, only 33% of people using the diet said it was “very” effective for weight loss.
- Almost half (46%) said it was a little effective
- Leaving 18% who said it was slightly or totally ineffective
Side-by-Side Study
Moving on to study data, an interesting side-by-side of vegetarians and non-vegetarians was conducted in 2022 for the International Journal of Environmental Research and Public Health. Here is a brief look at their findings.
Who the People Are
- 67% of vegetarians are female.
- 56% are white.
- The average age of a vegetarian is 36.
- They weigh, on average 7.85 kg (17 lbs.) less than non-vegetarians.
What they Eat
- Vegetarians eat 11% fewer calories.
- Vegetarians eat 46% more fiber.
- Vegetarians consume 34% less cholesterol.
Intermittent Fasting
Intermittent Fasting (IF), like its name implies, relies on a strategy of not eating at all, or strictly limiting calorie consumption, for a given period. During non-fasting periods, there are absolutely no restrictions.
- Some people fast on alternating days.
- Some fast for certain periods of every day.
Effectiveness
According to various studies and no less than the Harvard Medical School, the success of IF is hit or miss.
- Dropout rates are as high as 65% in clinical trials.
- Compared to simply limiting calories overall, IF had no statistical difference in weight.
- Dropouts in alternate day fasting are 9% higher than in calorie reducing diets.
- Meta-analysis of IF diets found between 0.8% and 13% body weight reduction; but they found similar results from simply restricting calories in a conventional manner.
Odds and Ends
- IF was the most searched diet term of 2019. [16]
- 24% of polled people said they have tried Intermittent Fasting (the largest group besides Atkins).
- A full 50% of people said IF was “very effective” (the largest positive response to any of the diets in the survey)
- 37% found IF at least somewhat effective
- 8% said it was ineffective, with another 3% saying “very ineffective”
- A separate survey [17] found that 75% of people have tried IF. Also:
- 80% of people are aware of IF.
- 43% of IF dieters fast between 16 and 23 hours per day.
- 41.8% responded that in less than a week they adapted to fasting.
- 38% said it helps “reduce weight”
- The Int'l Food Information Council, however, found only around 8% of people are on an IF diet.
Detox Diets
Detox diets are a large umbrella term for any diet that claims to “cleanse” the system. Because there are such a wide variety of detox diets, we’ll only use data from generalized terms.
According to the Int’l Food Information Council, less than 3% of all people are regularly on a Detox or Cleanse Diet.
A 2015 review of nearly all the scientific literature found no data suggesting any of them worked–none had weight loss, none actually eliminated toxins.
[18]
According to the National Health Service, of Britain, “Detox diets are marketing myths rather than nutritional reality.” [19] While we don’t have many statistics to report about detox diets, it appears that the survey, such as it is, from the medical community is in.
Weight Watchers
Perhaps seen as outdated by some, or not a true diet by others, Weight Watchers remains one of the most enduring and influential diets in the US.
- 21% of Americans have tried it at some point.
- 86% of all people who have used it found it at least somewhat effective. [20]
For what it’s worth, the same US News Survey of Experts we’ve been citing has Weight Watchers as the #1 Best Diet Program.
According to a study published in the Annals of Internal Medicine, Weight Watchers results in 2.6% greater weight loss than simple diet control and education, and should be recommended by clinicians to their patients.
Other Diets
The following is an incomplete list of other diets not researched here. Please leave a comment or email us if you would like more data about a specific diet:
- South Beach
- Pritikin
- Pasta
- Fit for Life
- Zone
- Cambridge
- Rotation
- Beverly Hills
- Junk Food
- Slim Fast
- Last Chance
- Jenny Craig
- Nutri-System
- Dukan
- Bodybuilder
References
