Studies have shown (1) that the use of hypnosis motivational suggestions produced an average 17 pound weight loss compared to half a pound weight loss in the control group after 6 months. A further study (2) showed including hypnosis in a weight loss program doubled the amount of weight lost.
1) Cochrane, Gordon; Friesen, J. (1986). Hypnotherapy in weight loss treatment. Journal of Consulting and Clinical Psychology, 54, 489-492.
2) Kirsch, Irving (1996). Hypnotic enhancement of cognitive-behavioral weight loss treatments–Another meta-reanalysis. Journal of Consulting and Clinical Psychology, 64 (3), 517-519.