Gastric Bypass Pre-Op Diet

A Gastric Bypass Pre-Op Diet generally begins two weeks before your surgery. You will be given a high protein liquid diet as preferred before gastric bypass surgery. Every surgeon will have his or her own preference, diet and instructions to follow .

I had Laparoscopic Roux en y Gastric Bypass Surgery.


This is the Gastric Bypass Pre-Op Diet I was given to follow.


800 Calorie Full Liquid Diet

For Two weeks Prior to Surgery

The reason for following this gastric bypass pre-op diet is to initiate rapid weight loss which will decrease the size of your liver. This will make the surgery easier for your surgeon to perform and safer for you. And prepare you for the weeks ahead after your surgery. During the post-op phase.


Below are 3 options that are recommended for the 800 calorie full liquid diet. If you would like to use other products pleaes discuss that with your doctor or your dietician .You need to meet the recommended  minimum of 60 grams of protein per day.

You should also include other liquids such as water, crystal light, decaf tea, sugar free gelatin and sugar free popsicles in addition to the 800 calories.


1.    4   ½ cans of High Protein Slim Fast daily


2.     5   1/2packets of No Sugar Added Carnation Instant Breakfast mixed with fat free or 1% milk daily


3.     4   ½ bottles of Glucose Controlled Boost daily.



If you have diabetes and are taking oral medications and or insulin you will need to discuss this with your doctor that manages your diabetes. Make sure to monitor your blood sugar levels more closely as this is a very drastic change in your diet. Call your doctor if you experience high or low blood sugars.

My personal journey...

Before your surgery you might be tempted to eat all kinds of things because you have that last meal mentality.          I know, I kind of felt that way. It was tempting to eat everything I felt like I might not ever eat again. I remember during that 2 week gastric bypass pre-op diet I had such mixed emotions. My surgery was getting closer and I was getting nervous and anxious at the same time along with being a little scared.   I felt kind of like it was my own personal test. Was I really ready to take this major step?  Did I want it enough to make the lifestyle changes needed to make it all work?  Yes I did!  I followed that diet !

Even though , I didn't have a lot of energy because of the gastric bypass pre-op diet, I did continue to walk daily thinking that would help me be physically in the best shape I could be in for the surgery itself.


This gastric bypass pre-op diet is vey important to follow. It gets you ready for the diet after your surgery and also  very importantly helps decrease the size of your liver before your surgery. This is critical for your surgeon to be able to see  and work around your liver with less chance of liver involved complications and injuries.