Here are a few formal research studies on hypnosis and weight loss.
The research is pretty clear that hypnosis supports weight loss, and more importantly supports long-term weight loss. The following are two studies that present some of the research into why this approach can work:
Study One: Bolocofsky, David N.; Spinler, Dwayne; Coulthard-Morris, Linda. Effectiveness of hypnosis as an adjunct to behavioural weight management. Journal of Clinical Psychology, 41 (1), 35-41.
The first study, published in the Journal of Clinical Psychology, divided 109 people into two groups for a 9-week study. The first group were treated with changes in diet and exercise habits without the addition of hypnosis. The second group was given the same diet and exercise treatment and was also given hypnosis for reinforcement.
After 9 weeks, not surprisingly, both groups lost weight due to the changes in diet and exercise while under supervision.
What happened after the 8-month and 2-year follow-ups were interesting. The group that did not have hypnosis did not lose any more weight and in fact, most gained most of their weight back. The hypnosis group, however, continued to lose weight during both intervals and the studies showed that far more people in the hypnosis group met their long-term weight loss goals.
The takeaway is that the hypnosis group continued the eating and exercise habits learned in the experiment while the non-hypnosis group did not.
Study Two: Kirsch, Irving Hypnotic enhancement of cognitive-behavioral weight loss treatments–Another meta-reanalysis. Journal of Consulting and Clinical Psychology, 64 (3), 517-519.
In this meta-analysis, (which is when researchers look across multiple studies), the results In the studies of hypnosis versus no hypnosis the average short-term weight loss was 200% better with hypnosis. Even more importantly, over the long-term, the average weight loss increased to 250% with hypnosis - indicating again that the effects of hypnosis seem to compound over time.