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.
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.
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. 
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.
Keto, like the Paleolithic diet, is hard for some people to understand. Here are a few basics:
High fat, moderate protein, very low carbohydrate.
The following are brief survey data. These are not collated from any one source, and the largest population surveyed was just over 1,000.
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.
More than twice as many Canadians drop Keto as stay on. Reasons given:
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.
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.
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.
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:
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:
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.
Turning to survey data, based on a poll by Yougov.
We’ll begin with basic survey data:
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
What they Eat
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.
According to various studies and no less than the Harvard Medical School, the success of IF is hit or miss.
Odds and Ends
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. 
According to the National Health Service, of Britain, “Detox diets are marketing myths rather than nutritional reality.”  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.
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.
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.
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: