No, I don't believe in this either.
In 2006 I went on a very low calorie program (something like 500cal/day) - based on shakes and water. It was coupled with group counselling and under close professional supervision. I lost about 65lb in about 5 months and that is a complete body makeover, trust me!
However, when I start eating food again, the weight started to pile up again, so the only way to keep it low would be to go back to drinking shakes for a month every 4-5 months - so it didn't really work.
What did make a difference however was the group counselling - it was then when I understood that although only me can lose the weight, I can only do it alongside with others.