Lowdown on the
Liver Diet Before Bariatric Surgery

Chances are you’ve heard talk about having to do a “liver diet before bariatric surgery.” And you might be freaking out about it! So let me break it down for you so it’s not so intimidating.

This is my professional advice on everything you need to know about the “how-to’s”:

  • HOW to do it
  • HOW it works
  • HOW long you have to follow it
  • HOW much weight you’ll lose


Ideally, you spend 3-4 months before surgery:

Then 1-2 weeks right before the surgical procedure you do what I call the “botta boom, botta bing,” a final pre op liver shrinking diet.   It’s a 2 week liquid diet plan right before surgery; the final thing to check off your to-do list so you’re optimally prepared for bariatric surgery.


You Have to Do a Liver Shrinking Diet

Find Out HOW the Liver Diet Before Bariatric Surgery Works

How Does it Reduce the Size of My Liver?

When you eat carbs, you burn some of them for immediate energy. The ones you don’t burn get stored so they can be used for energy later on in the future.

Carbs are stored in a form called “glycogen” in the liver (and muscles). When they get stored, water tags along with them and gets stored as well.

Recap: You need to eat some carbs to have energy. When you eat over and above what you need, the excess carbs gets stored in your liver in a form called glycogen, along with water.

Because glycogen is stored in the liver, the more carbs you overeat, the bigger the liver can become.

The liver diet before bariatric surgery is very low in carbs and calories. This forces your body to use up the glycogen you’ve previously stored up in your liver for energy. When glycogen gets released, so does all the water that was stored with it. The result: a smaller liver!

HOW LONG Do I Have to Follow the
Liver Diet Before Bariatric Surgery?

It depends.

Your surgeon may have a standardized recommendation. For example, they may require EVERY PATIENT to follow the presurgical bariatric diet for 2 weeks pre op. Or, recommendations may be based on your BMI. If so, it’s typically:

  • BMI > 50: 2-4 week pre op diet
  • BMI 40-49.9: 2 week pre op diet
  • BMI 35-39.9: 1-2 week pre op diet

Be sure to follow your surgeon’s guidelines at a minimum.

On a Liver Shrinking Diet?

You’ll likely lose weight, but that’s not the reason you do it. Remember the purpose of the diet is all about shrinking the size of your liver.

Results will vary and are dependent on several factors, including your starting weight. I’ve seen many patients lose between 5-20 pounds on the 2 week bariatric liquid diet pre op.

However, don't worry whether you’re losing “enough” or not. It’s really a better idea to stay off the scale!

HOW DO I FOLLOW the Liver Diet Before Bariatric Surgery?

The bariatric pre op diet is a low carb, very low calorie, high protein diet. Remember, it’s for the purpose of shrinking the size of your liver. How you actually follow it is another story. 

There are no standardized guidelines for the liver diet before bariatric surgery. That just means there are many ways to achieve a low carb, very low-calorie diet, high protein diet. There is not one right way ONLY! You have options.

  • OPTION 1: All Liquid Diet Using Approved Bariatric Specific Meal Replacement Shakes
  • OPTION 2: Mostly Liquid Diet Using Approved Bariatric Specific Meal Replacement Shakes + 1 food based meal (coming soon)
  • OPTION 3: Over the Counter Protein Shakes + 1 food based meal + 2 food based snacks daily (coming soon)

Liver Diet Before Bariatric Surgery:
The Takeaway

  • A low carbohydrate, very low calorie, high protein diet is used in the weeks before bariatric surgery to shrink your liver.
  • Remember WHY it’s important to have a smaller liver.
  • The liver shrinking diet is typically followed for 2 weeks pre op, although it may be a little shorter or longer depending on your surgeon’s guidelines.
  • You’ll likely lose weight on the liver shrinking diet, but that’s not the point. It’s really all about your liver.


  • There are no standardized guidelines for the liver shrinking diet, so you may hear and/or read varying recommendations about how to follow it. You have options.
  • …Although you have options, in my professional opinion, the ALL LIQUID approach to the pre op diet may be the best. It eliminates any confusion about what and how much to eat.

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