[sugarcube]

They might just work because they make it easy to eat less - very simple rule to follow that rules out most unhealthy snacking.

[weego]

When you look at ketogenic diets being used to control epilepsy you realise there is likely more to it than just behavioural.

[martinko]

You're also less hungry when you restrict carbs (bread, pasta, sweets, etc.).

[lsniddy]

They also might just work because they train your body to run off its energy reserves. Even in a "healthy" high carb diet, you are still requiring a constant intake of fruit/grains.