There are many, many people who have lost 100 pounds and kept it off.
I was gaining weight very rapidly and read about the idea of restricting carbohydrates as an alternative to going hungry. I had a big appetite, so that was the only thing I would even consider.
My patient population has a low recidivism rate, but if they haven't made up their minds that it is permanent, then of course, they will fail.
It's so logical and so simple. Fat is the backup fuel system. The role it plays in the body is that when there's no carbohydrate around, fat will become the primary energy fuel. That's pretty well known.