It's hard for me to take something like this seriously.

If, after losing weight, these people are driven to consume more calories than their bodies are expending, they need to do something to compensate for that, plain and simple. It could be exercise or it could be gaining muscle mass (and maintaining muscle mass requires more caloric intake than maintaining fat).

It's an absurdity to believe that these people should be able to lose weight, then simply go back to being sedentary and eating what they want to eat and expect to keep it off.