I just got a nutri-bullet for Christmas and have been experimenting with recipes of veggies and fruit. My NUT seems to think it is good for me and has not said anything about not using it. Many folks nowadays who are pre-op are doing liquid fasts such as in a liver detox and are making healthful shakes. I plan to use it anyway. i have gained 100 pounds since my RNY 14 years ago-- mostly due to having had my thyroid out- which is the center for metabolism. Just recently got scoped and the doc says my pouch holds 10-12 oz of food now-- I would like it to be made smaller--however i think they will put me on a liquid diet first. So with the nutri bullet I am putting in a flavorless Protein powder to help with the protein issues.