A woman came to see me and she said. “I weigh 180 pounds. I’ve dieted successfully under doctors’ orders hundreds of times.  And I wand to weigh 130 pounds. Every time I get to 130 pounds I rush in to the kitchen to celebrate my success. I put it back on, right away. Now I weigh 180. Can you use hypnosis to help me reduce to 130 pounds? I’m back to 180 for the hundredth time.”
I told her, yes, I could help her reduce by hypnosis, but she shouldn't like what I did.
She said she wanted to weigh 130 pounds and she didn’t care what I did.
I told her she’d find it rather painful.
She said, “All right. I want an absolute promise from you that you will follow my advice exactly.”
She gave me the promise very readily and I put her into a trance. I explained to her again that she wouldn’t like my method of reducing her weight and would she promise me absolutely, that she would follow my advice? She gave me that promise.
Then I told her, “Let both your unconscious mind and your conscious mind listen. Here’s the way you go about it. Your present weight is now 180 pounds. I want you to gain twenty pounds and when you weigh 200 pounds, on my scale, you may start reducing.”
She literally begged me, on her knees, to be released from her promise. And every ounce she gained she became more and more insistent on being allowed to start reducing. She was markedly distressed when she weighed 190 pounds. When she was 190 she begged and implored to be released from her own promise. At 199 she said that was close enough to 200 pounds and I insisted on 200 pounds.
When she reached 200 pounds she was very happy that she could begin to reduce. And when she got to 130 she said, “I’m never going to gain again.”
Her pattern had been to reduce and gain. I reversed the pattern and made her gain and reduce. And she was very happy with the final results ad maintained that weight. She didn’t want to, ever again, go through that horrible agony of gaining twenty pounds.
For this patient, the gaining of weight is no longer either rebellion or an expression of something she wants to do. it has become something she has been coerced into doing. Therefore, just as she had previously resented having to lose weight, she now resents having to gain weight.
[…] Here he [Erickson] shows that it is often helpful to get patients to change their pattern. In this case, he simply had the woman revers her pattern of reducing and gaining. Once he had done this she could no longer go through the same sequence repeatedly, as she had done all her life. She apparently had learned to be able to tolerate gaining weight only up to 180 pounds. We see this in many weight patients. They have a level of tolerance, at which point they urgently feel the need to reduce. Erickson succeeded in making this tolerance level intolerable because he made her go beyond it.
This method of reversing patterns or looking at things in a reverse way is one of Erickson's favorite approaches for changing mental sets. He liked to show patients a book called Topsys & Turvys, by Peter Newel, in which the stories and the illustrations change meaning when the book is turned upside down.
Taken from Milton H. Erickson. My Voice Will Go With You, p. 123, W.W. Norton – New York; London.