The most successful diets, memetically, are those which fail to cause permanent weight loss.
To quote Aaron Lynch in "Thought Contagion":
The more often adherents diet, the more often they retransmit the memes. By failing to change long-term habits, a dietary meme set can actually induce those episodes of recurrent dieting-- and recurrent meme dissemination. The 'defective' memes thereby grab a proselytic edge over more permanent weight-control methods.
During a diet, dieters often proselytize, because of the volume of research they have gathered on the diet, because of their enthusiasm over new weight loss, and because they want cooperation from their friends in remaining faithful to the diet. During the period of weight loss, recipients of the meme are encouraged to notice the dieter's weight, and to present compliments in the presense of friends (other potential diet meme hosts).
If a diet kept weight off, it would only enjoy this period of virulence once with each dieter. If, however, the weight is regained, it has the opportunity to go through another cycle of proselytizing with the very same host.
During the period of weight gain, the diet is not mentioned, and is therefore not blamed. The meme is inactive. | 
