Pre-Op Diet Before Gastric Sleeve Surgery

pre-op diet for gastric sleeve

Do I have to follow a pre-op diet before the gastric sleeve procedure? What am I allowed and not allowed to eat before my gastric sleeve? What if I cheat on my pre-op VSG diet? These and other questions are answered in detail in our today’s post about the gastric sleeve pre-op diet.

Choosing to have bariatric surgery is a huge step in becoming a healthier you! This surgery is going to be the beginning of a lifelong journey and will require many dietary adjustments both before and after the surgery. Some important changes need to be made as soon as possible to help prepare you for safer surgery, and also to jumpstart your weight loss process.

Do You Have To Do a Pre-Op Diet For Gastric Sleeve (VSG)?

Every surgeon will have different pre-surgery requirements but all of them will include a clear VSG pre-op liquid diet at some point before surgery as well as the “nothing after midnight before your surgery” rule. This is a safety requirement when having surgery under general anesthesia and is needed to prevent aspiration of anything in your stomach, which can cause pneumonia or even death.

Aside from the normal after midnight fasting before surgery, your surgeon may require you to make some changes to your diet before your gastric sleeve surgery. The exact details of the requirements will vary depending on which type of gastric sleeve surgery you are having (surgical or non-surgical), the state of your overall health, and your surgeon’s professional preferences.

What Pre-Op Diet Should I Follow?

Each surgeon will have their own dietary recommendations and general guidelines for their patients, and also specific, individual requests for each patient. The length of the diet and the list of foods/liquids allowed will be based on each patient’s BMI and other determining factors.

Gastric Sleeve Diet before Surgery to Lower BMI and Post-Operative Risks

Some patients will be on a very strict vertical sleeve gastrectomy pre-op diet before the procedure to further reduce the risks of complications. A recent study revealed that the higher a patient’s body mass index (BMI) is, the higher their chances of post-operative complications are.

The study indicated that associated risks increased by app. 2% for each additional BMI point. These are important statistics and should motivate patients to work on their BMI to reduce their chances of post-operative complications.

General BMI Guidelines for Pre-Op Bariatric Diet

Since we understand that higher BMIs increase the risk for complications related to surgery, it makes sense that the duration of a pre-operative diet to reduce BMI before surgery should be longer for individuals with a higher BMI, and shorter for those with a lower BMI. Here is a handy chart that gives a basic (approximate) outline of what it would look like (please remember that it will vary by every patient).

Pre-Op Gastric Sleeve Diet Duration Chart

BMI Level Pre-Op Diet Duration
Under 38 Most likely exempt from the VSG pre-op diet but will follow the 2-day “liquid only” diet just before surgery.
38-39.9 One week
40-44.9 Two weeks
45-49.9 Three weeks
50 and over Four weeks

Shrinking Your Liver Before Gastric Sleeve Surgery

Another reason the pre-op diet before gastric sleeve surgery is very important is that it will help provide a successful outcome. Your liver sits on top of your stomach and has to be “worked around” during the gastric sleeve surgery.

Often, unhealthy eating causes the liver to be enlarged and can make it difficult for the surgeon to safely access the stomach. Your pre-surgery diet will help shrink the size of the liver making it more manageable for the surgical team and safer for your surgical outcome.


What Can I Eat the Weeks Before Gastric Sleeve Surgery?

The exact answer to this question is up to your surgeon. However, for most patients, this means:

  • a very low-calorie diet that is high in protein for a specific amount of weeks before the surgery;
  • a total liquid diet for the last 2 days before the surgery;
  • nothing at all to eat or drink for the 8 hours before the surgery.

Pre-Op Gastric Sleeve Diet and Allowances per Day (Example)

1 Protein shakes 1-2 per day store-bought or homemade*. Must contain:

  • At least 20 grams of protein per serving;
  • No more than 5 grams of sugar.
2 Raw or cooked non-starchy vegetables without limit, excluding potato, corn, or peas.
3 Lean protein two 4-7 ounce servings. i.e. fish, turkey, or very lean ground beef.
4 Healthy fat 1-2 servings, i.e. olive oil, nuts, olives, or avocado.

*Protein shakes can be made only with almond milk or coconut milk that are unsweetened, but you can add ½ cup of fresh or frozen berries or ½ of a banana.

Not Allowed
1 Rice, bread, pasta, tortillas (all refined grains).
2 Sauces with sugar.
3 Anything dairy, i.e. yogurt, cheese, milk, etc.
4 Alcohol.
5 Nicotine, products that contain THC, marijuana. Smokers can ask their doctor for medication to help with nicotine cravings if necessary.

Liquid Diet before Gastric Sleeve Surgery

If you are given a 2-week “liquid-only” diet before your surgery, you may experience some unpleasant but completely normal symptoms. Your body will get used to the reduction in calories and will adjust to alleviate these symptoms after the first 3 – 4 days. Drinking at least a gallon of approved beverages/liquids a day will help keep you hydrated and reduce the severity of these symptoms:

  • Hunger pains;
  • Fatigue/weakness;
  • Headache;
  • Stomach upset including nausea, constipation, or diarrhea;
  • Mood swings.

Schedule for Pre-Gastric Sleeve Surgery Dietary Restrictions

Time Before Surgery Pre-Op Diet Restrictions
1-4 weeks Follow the surgeon-recommended diet.
2 days Follow surgeon-provided instructions (some allow clear liquids only while others allow broths).
8 hours Nothing to eat or drink! Nada, zilch, zero! This is very important for your safety during surgery. If you cheat on this, the surgeon will probably cancel your procedure, it is THAT serious.

What Happens if I Cheat on My Pre-Op Gastric Sleeve Diet?

The pre-op diet is critical for two reasons:

  1. To shrink your liver to prepare for the surgery and;
  2. To empty your stomach and intestines of all contents to ensure a safer surgical experience.

The main reason you are asked to follow a specific diet before a surgical procedure is to ensure your safety, so you are not doing yourself any favors if you cheat. Not following the required diet may result in negative consequences. The medical team will be monitoring your BMI in the weeks leading up to your surgery so if they are not seeing the required improvements, they may re-schedule your surgery.

If your surgeon begins the laparoscopic gastric sleeve procedure and can not gain access to the stomach due to an enlarged liver, they may stop the surgery and postpone it until a later time. It would be disappointing to have made it that far just to have to repeat the process at a later time.

Will I Continue to Take My Normal Prescribed Medications?

Each patient is unique and has specific health and medication needs so a consultation with your surgeon about medication is critical when discussing pre-operative instructions. Make sure you discuss all the medications you are currently taking with your surgeon. It may be necessary to suspend or modify the medications you are taking (or the dosage) before surgery and possibly even after.

Some over-the-counter medications and herbal supplements should also be discontinued before surgery as they may encourage bleeding. Ask your surgeon for instructions related to specific medications and supplements.

What If I Can’t Follow the Pre-Op Diet for Gastric Sleeve Surgery?

Pre-op diets begin preparing the patient both physically and mentally for the major dietary changes that are necessary for weight loss surgery to be successful. Even though the focus of the pre-op diet is to mitigate surgical risks, it is also the beginning of the dietary commitment you are making when you decide to have any type of bariatric surgery.

A major change to your diet before and after gastric sleeve surgery is not something you can eliminate from the equation. Dedication and a firm commitment must be made by the patient for any type of bariatric surgery to result in health-altering results. If you feel that you will not be able to follow a short diet to prepare yourself for a safe surgical procedure, you need to consider if you will be able to maintain the dietary restrictions required after the surgery. It is not going to be easy but it is possible. Others have successfully done it, and you can too!

If you are looking for answers related to bariatric surgery, you are in the right place! We are here to help you with your weight loss questions and would value the opportunity to help you on your journey to wellness. Contact IBI Healthcare Institute for a consultation today to find out more. The day you have your consultation is one day closer to a healthier you.

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