Bariatric Pre Op Diet:
Preparing for the Big Day

bariatric diet questions mark

Welcome to the wild and wacky world of the bariatric pre op diet! You're probably wondering, "What is this diet?", "Why do I have to follow it?", and "What happens if I cheat?"

Well, let me tell you, it's a diet that's not just about looking good, it's about making you surgery ready. And if you cheat, let's just say, it won't be pretty. But don't worry, I'm here to guide you through it all, as your trusty bariatric dietitian.

Let's start with...

The "WHATs" of the Diet

The bariatric pre op diet is a low-carb, high-protein, very-low calorie diet.

Typically, you consume 800-1,000 calories per day (sometimes up to 1,200 if you're lucky). 

Now, I know what you're thinking, "But I can't even lose weight on my own, why do I have to follow a diet before surgery?" 

Don't fret...Let me explain the "why."

WHY Do I Have to Follow It?

The goal of the bariatric pre op diet is less about weight loss and more about shrinking your liver.

The pre-op diet is also known as the "liver shrinking diet" because its main goal is to make your liver smaller and easier for your surgeon to maneuver during the surgery. Think of it as a warm-up before the big game. The smaller your liver, the easier it is for your surgeon to perform the procedure, and the easier it is for you to recover.

Now let's talk about...


  • Some insurance companies require a “medically supervised/physician monitored diet” for 3-6 months prior to surgery. This is different from the short-term liver reducing preop diet.
  • See how to start making lifestyle changes in the 3-6 month appointments before surgery

The Elephant in the Room:
Cheating on the Bariatric Pre Op Diet

We've all been there, tempted to sneak in a bite of our favorite foods. 

Well, I'm here to tell you that cheaters never win...and winners never cheat...but let's be real, we're all human and sometimes get tempted to cheat and sneak in a bite or two (or three) of our favorite foods. But please, for the love of your liver and your pocketbook, try not to cheat on this diet.

Before you give in to temptation, remember the potential consequences:

Your surgeon may have trouble getting to your stomach. This means longer surgery. This means increased time under anesthesia. This means higher hospital bills. Possibly a longer hospital stay.

Also, it’s possible your liver could crack or bleed when it’s lifted, then injure other organs. Worse case scenario is that the bariatric surgery procedure would have to be aborted then to fix your liver or other damaged organs.

OR your surgery could wind up being converted to an “open” surgery vs “laparoscopic” surgery. That also means bigger hospital bills, longer hospital stay, bigger scars and longer healing time.

Cheat at your own risk. 'Nough said. 

Do your best to stick to the diet and reach out for support if you need it.

Cheating on Your Pre Op Diet:

Longer surgery

Increased time under anesthesia

Longer hospital stay


Liver cracks or bleeds when lifted

Other organs subsequently damaged

Surgical procedure aborted to fix other organs


Must convert to “open” surgery

Higher hospital bills

Bigger scars

Longer healing time

Bariatric Pre Op Diet:
The Bottom Line for Your Bottom Line

  • The goal of the bariatric preop diet is less about weight loss and more about your liver. It’s also called a "liver shrinking diet."
  • Your liver is located above your stomach. If it’s too big, it can make it difficult for your surgeon to see and access your stomach during your procedure.
  • The bariatric pre op diet should be taken seriously. There are a number of negative outcomes that could occur if you go into surgery with an enlarged liver.

The bariatric preop diet may sound daunting, but it's an important step in ensuring a smooth surgery. Remember, it's just 2 weeks and you can do anything for a short period of time! So, take it one minute at a time and before you know it, you'll be on the other side of this diet and one step closer to your happy dance.

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