Over the years, diet fads have continued to fill our lives with false hope of losing weight the easy way. Diets including Atkins, the Zone, South Beach, the Low-fat, the Baby Food, the Japanese Food, and the Tabasco Diet have all come and gone, each of them having their time in the limelight as The Diet that works. However, most of these diets are fads and do not give people the results they had hoped for. So why do people still believe the absurd diets that are out there? After so many failed attempts at losing weight, why do even the most ridiculous diets still gain popularity?
As John Tierney, a writer for the NY TImes, explains, diet fads are all “informational cascades.” According to Tierney, cascades “can be based on correct beliefs as well as mistaken ones.” These mistaken beliefs are what causes a particular diet fad to start. Desperate people who are seeking any easy way to lose weight are usually the instigators of diet fads. For example, someone desperately wanting to lose weight may come across a new “fad diet” while reading a magazine. Since this person has not tried this diet yet, she figures it can’t hurt to try, so she does. After a week of dieting, a friend of the dieter notices she has lost some weight. They discuss the diet and the friend decides she will test it out. This cycle continues on, more and more people begin using the diet, and soon enough the diet will become well-known.
However, as with most diets, weight-loss usually only lasts a few weeks, and after that it is much more difficult to keep the weight off. As a result, people begin to gain back the weight they lost. If this begins to happen with the “fad diet,” people will stop using it and it will slowly lose its popularity.
This example is exactly how information cascades develop. Tierney explains in his article that once a large group of people starts a trend (in this case a fad diet), the rest of the people (those seeking new diets) decide to go along with the trend because they figure the “trend-setters” can’t all be wrong; therefore they must be right. Moreover, Tierney clarifies that most decisions people make are binary (e.g. endorsing a diet or not endorsing it). This actuality makes decision-making uncomplicated, and also allows for trends and fads to cascade more rapidly.

http://tierneylab.blogs.nytimes.com/2007/10/09/how-the-low-fat-low-fact-cascade-just-keeps-rolling-along/

http://www.suntimes.com/lifestyles/wiser/877379,CST-FTR-lifediet04.article