Gastric Sleeve Pre-Op Diet: How to prepare for your surgery day

By Derek
My Gastric Sleeve Pre op Diet

So you’re having the Vertical Sleeve Gastrectomy (VSG) soon?

Are you preparing as you should to be ready for the big day?

Preparation for bariatric surgery is multi-faceted. You have to prepare mentally as well as physically in order to get the results that you need.

The problem is that most people tend to focus on the POST-op part of bariatric surgery. But it starts with PRE-op preparation to lay the foundation for success post-op.

This primarily comes in the form of the pre bariatric surgery diet. It’s specific and short and it makes all the difference in the world.

Why a Gastric Sleeve Pre-Op Diet is Important

There are two primary reasons why you are instructed to follow your pre-op diet before you have gastric sleeve surgery:

  1. It helps you lose weight before your surgery
  2. It reduces the size of your liver

Both of these reasons are critical to the success of your surgery to help you avoid unnecessary compilations that could seriously impact your health in a negative way.

The pre bariatric surgery diet (for all procedure types) is classified as a Very Low Calorie Diet (VLCD). As it sounds, the diet is low in calories, but it’s also high in protein. Higher protein intake is associated with lower BMI.

Protein also helps preserve lean body mass (like muscles) during times of extreme calorie restriction.

Losing weight before gastric sleeve surgery

Woman is encouraged because she reached onederland

It has been documented that the higher a patient’s BMI the more likely they are to experience complications.

BMI Stands for Body Mass Index and it’s a quick and effective way for medical professionals to determine a patient’s level of obesity.

In fact, this study found that the odds of postoperative complications increased by 2% with every point increase in BMI. So for every single BMI point decrease, you can accomplish before surgery you significantly decrease the chance of post-op complications.

The proper diet leading up to your sleeve gastrectomy surgery is particularly effective at producing rapid weight loss as quickly as possible, while still being safe.

Shrink the liver before gastric sleeve surgery

Why do I need to follow a liver shrinking diet before bariatric surgery?

The liver is an organ that is responsible for bodily tasks like breaking down fats, carbohydrates and proteins that can be used in the body, as well as removing toxins from the body.

The reason for bringing up the liver as we talk about a gastric sleeve pre-op diet is because the liver actually sits on top of the stomach. This means that the surgeon and the surgical team have to physically lift up the liver so that the surgeon can access the stomach.

Since the sleeve gastrectomy only deals with the stomach, it’s important that the liver is of a manageable size.

How you eat leading up to your surgery actually has a profound effect on the size of your liver.

By eating the right way and eating the right foods you can actually shrink the size of your liver and make the surgery easier on your surgeon and her team.

So by following your gastric sleeve pre-op diet you are helping yourself out quite a bit. It’s normally no longer than 4 weeks, and you can do ANYTHING for 4 weeks, right?

Gastric Sleeve Pre-Op Diet Preview

Overview of the Gastric Sleeve Pre-Op Diet

How Long is the Gastric Sleeve Pre-Op Diet?

The duration of your pre-op diet is determined by your current BMI. Like we learned a moment ago, the lower your BMI, the lower your chances of complications happening. So it stands to reason that the higher your BMI, the longer you’ll be on the pre-op diet.

Specifically, here’s how the diet-duration relates to BMI values:

  • BMI < 38: Exempt from the diet, but you will follow the 2 days of liquids prior to surgery*
  • BMI 38 – 39.9: You’re on the diet for One Week
  • BMI 40 – 44.9: You’re on the diet for Two Weeks
  • BMI 50 – 49.9: You’re on the diet for Three Weeks
  • BMI > 50: You’re on the diet for Four Weeks

Here’s a simple calculator to see how long you will likely be on the pre op diet.

2 Days Before Gastric Sleeve Surgery

2 days leading up to gastric sleeve surgery

Up until this point you’ve been following the pre bariatric surgery Very Low Calorie Diet (VLCD) with the goal of losing weight and shrinking the liver.

But now that you’re a mere 2 days from surgery, what’s the goal? What are the diet prescriptions for this point in the pre-op journey?

Since the surgeon will be working on your stomach and around the intestinal tract, it’s EXTREMELY important that there is no food or other residue in your stomach or intestines.

Think about it…would you want food and other residues to accidentally fall into your body cavity during surgery?

Hello, infections!

So, 2 days leading up to surgery it’s generally recommended to follow a liquids only diet. Some practices specify “clear liquids” only, but it’s tough to get enough protein that way. That’s why we say “liquids only.”

This way you can make use of protein soups and broths. It’s the best of both worlds because you get your fluids, you’re not causing residue build-up in the GI tract AND you’re getting protein.


Your surgeon WILL know within minutes if you followed your pre-op diet and did liquids only leading up to surgery.

Surgeons in surgery talking about how the patient didn't follow the gastric sleeve pre op diet

That’s how much your liver can shrink AND how long food residues linger in your system. You don’t want to disappoint your surgeon, do you?

8 Hours Before Surgery

8 hours leading up to gastric sleeve surgery

Nothing, zilch, nada.

If your surgery is scheduled for 8:00 AM then you must not eat or drink anything past 12:00 Midnight the night before.

This is for 2 reasons:

  1. You don’t want to have anything in your stomach since you’re having surgery on your stomach
  2. When you are under general anesthesia your body’s normal reflexes are put on pause so there is a chance for complications due to the anesthesia

So no food or drink at all during the 8 hours leading up to surgery, which should not be a big deal since you’ve been on liquids only for the previous two days.

Medications Before Gastric Sleeve Surgery

You may need to modify your medications and their dosages prior to surgery.

This is absolutely, unequivocally something that you need to discuss with your surgeon and primary care physician. No amount of reading online will give you an adequate answer.

You are a unique individual with specific health and medication needs and only medical professionals who are fully aware of your health and needs can make that call. Also, don’t change anything about your medications without the guidance of your medical team.

What we can do is tell you to ask them, and you should!

Talk to your surgeon about your medications because you may need to modify your dosages in the days leading up to surgery. That’s something only they can help you with.

A Simple Gastric Sleeve Pre-Op Diet

Your dietitian may have a pre-surgery protocol, but if you need one we have turnkey options that you can order today. They include everything you need in the perfect amounts so you don’t have to do any shopping or guesswork no matter how long you need to be on the diet.

Bari Life pre bariatric surgery liver shrinking diet bundles

All you need to do is order the bundle that corresponds to your required pre-op diet duration, follow the instructions and you’ll be ready for surgery!

The Bottom Line on the Gastric Sleeve Pre-Op Diet

No matter what bariatric procedure you’re having, you must follow a pre bariatric surgery diet in order to properly prepare yourself for surgery.

It’s not something you can get around and if you cheat on the pre-op diet your surgeon will know – and in some cases cancel your surgery – if they think it’s going to compromise your health and safety.

Take this seriously and follow it to a “T.” It’s such a short period of time in the grand scheme of things. Remember why you’re having surgery and use your goals as motivation to stay the course.

You got this!


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