Bariatric Pre Op Diet:
Professional Answers to the "Whats" and "Whys"

bariatric diet questions mark

Chances are you’ve heard about, and are dreading, the bariatric pre op diet. You may have heard it’s a 2 week liquid diet plan. The thought of drinking only liquids for a couple of weeks might sound dreadful, I know.

I can show you HOW to do it and help you understand you have options.

But first, let me help you understand the “WHATs” and WHYs” of the bariatric pre op diet so it’s a little less intimidating:

  • WHAT is the 2 week pre op diet all about?
  • WHY must I follow it?
  • WHAT if I cheat?

And WHAT you can eat and drink, WHAT to avoid, WHAT to expect

Bariatric Pre Op Diet

The pre surgical bariatric diet is a:

  • Low carbohydrates
  • High protein
  • Low fat
  • Very Low Calorie Diet

Typically, 800-1,000 calories per day. Sometimes up to 1200 calories per day.

It’s followed in the weeks immediately preceding your surgery.

I know what you're thinking...

...I'm having weight loss surgery because I can't lose weight. Why in the world do I have to follow a PRE bariatric surgery diet when I can't lose weight in the first place?!

The goal of the bariatric pre op diet is less about weight loss and more about your liver. The preop diet is also commonly called a “liver shrinking diet.”

Bariatric Pre Op Diet
WHY Do I Have to Follow It?

Your liver is located above your stomach. During surgery, it must be lifted and moved out of the way so your surgeon can see your stomach lying beneath it. If your liver is big and fatty, your surgeon will have a harder time seeing your stomach and getting to it to perform the procedure. An easier surgery for your surgeon translates to easier surgery for YOU ;)

Pretty much every surgeon therefore agrees you should follow some version of the liver shrinking diet. However, there are many way to deliver a low carb, high protein, low fat, very low calorie diet:

  • All liquids
  • Mostly Liquids
  • Some Liquids + Some Food

The truth is, there are no standardized guidelines for the bariatric pre op diet. So the prescriptions on how to adhere to it vary wildly. If you follow other people’s surgery journeys on social media, you may have already witnessed that recommendations differ quite a bit from surgeon to surgeon. That’s why.

Bariatric Pre Op Diet
WHAT if I Cheat?

“Cheaters never win and winners never cheat. Hogwash!”  Actually, I still remember that was the first sentence I wrote in an essay that was assigned as my punishment when I got caught cheating on a 7th grade Texas History test. True story! (And I Remember the Alamo! )…But I share my embarrassing story to convey we’re all human, and…

…we can be tempted to cheat!

In the case of your presurgical bariatric diet though, I’d suggest doing a little better than I did in 7th grade. Rise to the occasion. It’s just 2 weeks. Keep telling yourself that. You can get through anything for a short period of time. Take it minute by minute, hour by hour if you must, and the 2 weeks will be done before you know it.

If you really DO cheat and go into surgery with a big fatty liver:

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.

Do your best not to cheat. Reach out for support if you need to. I can help you get through it!

Potential Consequences of “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


  • 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

Bariatric PreOp Diet:
The Takeaway

  • The goal of the bariatric pre op diet is less about weight loss and more about your liver. It’s considered 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 prescriptions on how to adhere to the bariatric preop diet vary wildly from surgeon to surgeon because there are no standardized guidelines.
  • 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.

Like This Info? Allow Me to Join You on Your Journey!
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