A fad diet is usually called  a diet which  comes and goes within a short amount of time.   Many other similar diets had a brief popularity and disappeared.  Some of them worked for certain people, did nothing for another group, and caused problems in a third group. The Atkins Diet, for instance, can be referred to as a fad diet. Atkins Nutritionals, Inc. filed for bankruptcy protection in July 2005. Other fad diets  are  South Beach, the Zone, or other protein-packed regimens, dieters were dropping pounds while eating rich, low-carb foods such as butter, steak, and pepperoni pizza (but without the yummy crust). Now the trend has shifted, as it always does with fad diets. 

 American Heart Association issued the following statement about fad diet