The point is to help a person get used to eating a lot less, and when they hit their target weight, they can continue with their new eating habits.

But if you go back to the same eating habits that made you fat, you're gonna get fat.

I've dropped 100 pounds over about 3 years (and still dropping), without any drugs, because I taught myself to get by with much smaller portions. Partially it came from eating only when hungry, not bored.

The other, possibly more important thing was using a distraction, so when I'm tempted to go see what's in the fridge, I pick up my guitar instead. So I've lost a lot of weight, AND learned to play the guitar at the same time. Replacing a bad habit with a good one is very effective.