In this study, 109 people participated in a 9-week study. One half of the group participated in a typical diet-and-exercise program. The second half of the group got the same diet and exercise treatment and also received hypnosis for reinforcement.
After 9 weeks, participants in both halves lost weight. In 8-month and 2-year follow-ups, the group that had only the diet-and-exercise program lost no weight after then end of the initial study, and most of those participants had gained back most of the weight they had lost.
The hypnosis group, however, continued to lose weight after the end of the initial study, and far more people in the this group met their long term weight loss goals.
Read the abstract here.