When I met with the nutritionist she suggested to start following a low carb diet asap. Found a book;

Carb addicts diet. Been following it and have lost 9.5 pounds since 10/13. Not going hungry by any means, hope this will have the sugar/salt cravings gone by pre op diet. Today was a good day.

I hope they are just suggesting low-carb as part of a pre-op diet. While a low carb diet can give you quick temporary weight loss it's not to good to do over a long period of time. Since it concentrates on higher fats and proteins and restricts fruits and vegetables it can lead to high cholesterol, vitamin and mineral deficiency, cardiac, renal, bone, and liver abnormalities. You really need to eat a well balanced diet just in smaller quantities.