The thing about diets is that everybody has got one that worked for them.

It seems to me that the one thing all of these different diets have in common is that they require the person to monitor what they eat. Whatever the specifics of the diet, the dieter ends up paying more attention to their meals in general and that extra digilgence translates into reduced caloric intake.

I'm not making a judgment on the nutritional value of any particular diet, just the underlying mechanism for why different diets all have somebody claiming that they work.

Even the twinkie diet: http://www.cnn.com/2010/HEALTH/11/08/twinkie.diet.professor/