Weight gain and the inability to lose weight can be a very frustrating, depressing and life threatening problem.
Most of the time when a person has spent a long time trying to lose weight and has failed, time and time again, it is due to underlying feelings that have gone unresolved. The body and mind has determined that the best way to cope and protect itself from whatever feeling is hidden away is to eat / over-consume.
The subconscious mind is magnitudes more powerful than conscious thought and emotion is magnitudes more powerful than willpower.