What are you talking about? If you eat a diet that has the required number of calories and nutrients designed for a healthy-weight person, your body weight will drop accordingly.

The factors that lead someone to overeat is a totally different question the answer to which should be figured out by themselves or maybe their psychologist. In most cases it's not that dire though, once their initial withdrawal from fast food stops people stop having these impulses to reach for a doughnut each time they're inconvenienced. In any case, your problems in life should be treated by dealing with the problems directly and not making themselves feel better by stuffing their face.