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Post Op Gastric Sleeve Diet


A little known fact is that in addition to the required diet after the gastric sleeve surgery, there is also a preoperative diet.


It is important to note that the diet should be done by patients who have a high Body Mass Index, above 35. Patients with BMI under 35 can go forward with surgery without the need of doing this gastric sleeve pre-op diet.


Preoperative gastric sleeve diet is as important as the postoperative diet because it is part of the preparation necessary for the patient who will undergo gastric sleeve surgery.

There are multiple ways to carry it out and the exact diet you should follow is directly related to the bariatric group where you decide to have surgery, so it is difficult to provide specific guidelines on what constitutes this diet.


What we can share with you is what we do in Obesity Free and how we decide the duration and characteristics of the gastric sleeve preoperative diet:


When a patient is already in the process for surgery with us, we need to know exactly your current weight to take it as a starting point in planning / duration of the diet, which although could be considered strict, based on our experience we believe that is the best way to introduce the patient to the new lifestyle that is about to begin.


The diet we give our patients in the gastric sleeve preoperative stage is basically a strict liquid diet.


Content of this article:
Why a Preoperative Liquid Diet?
What can you take?
Why is this diet necessary?


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Why a Preoperative Liquid Diet?


A liquid diet is essential to prepare the body in order for the surgery to be successful and the best possible results to be achieved. It serves as a form of mental and physical preparation of the body for the change that a new lifestyle and new eating habits represent. However this does not mean that the patient will have to be on a liquid diet for life.


Most liquid diets are not suitable as a long-term treatment to achieve significant weight loss; however, they are of great benefit for certain types of procedures such as bariatric surgery, during the preoperative and postoperative period. Despite being very strict, the efforts are quite worthwhile, as mentioned later in this article.


People who are about to undergo a bariatric procedure such as the gastric sleeve may be requested to perform this diet, which will be determined by the surgeon depending on certain factors, being the main factor the Body Mass Index (BMI).


Patient’s BMI will determine the time needed to do the diet before surgery, at Obesity Free we rely on our own rule:




  • 35 or less, it is not necessary, unless the patient has deemed prudent to do it a few days before surgery to prepare psychologically
  • 35 to 42 liquid diet for one week
  • 42 to 45 liquid diet for two weeks
  • BMI of 45 or more, we rely on the patient's weight in pounds, for example a patient weighing 300 lbs will require three weeks, 400 lbs diet for 4 weeks and so on.



What can you take?


Make sure that you include in your liquid diet fluids that are sugar free or low in sugar and calories. The idea is that your diet should be high in protein but low in fat and carbohydrates and therefore low in calories too.


Some of the fluids you can include in your diet are:

  • Water
  • Gatorade ®
  • Propel ®
  • Any other "sports" drink
  • Crystal Light ®, Clight ®, etc.
  • Dark coffee, preferably decaffeinated
  • Fruit juices without sugar or low sugar
  • Tea / Iced Tea
  • Sugar free gelatin (Jello®)
  • Slim-Fast ® shakes low in carbs
  • Atkins ® Malts
  • Beef, poultry or vegetable broth (bouillon),  (* This will be one of the few but important sources of protein during this period).
  • Water with proteins like: Special K ® O2 or similar
  • Any whey protein powder, 100% combined with water or skim milk. These products can be found at health food stores like GNC®  (Isopure whey protein Isolate ®, Myoplex ® Lite, Myoplex Carb Control ®, etc.)
  • Sugar free water Popsicles
  • Kool-Aid ® unsweetened Tang ® unsweetened , etc..
  • Carnation ® Instant Breakfast Sugar made with skim milk
  • Soups / low fat creams (example: Campbell's ®) with skim milk

** You can use the whey protein powder as a substitute for a full meal, three times a day, supplementing with other options during the day. Mixing this powder with skim milk tastes better than with water.


**Being only liquids  it can seem that there is no way to overdo but it is possible, so you must ensure that the total intake of calories per day does not exceed 1000 calories.



Why is this diet necessary?


In the pre-operative period, a diet mainly consisting of clear liquids has many functions such as reducing the size of the liver and bowel cleansing this helps decreasing “stress” on the digestive system.


This gastric sleeve preoperative diet can represent the success or failure of your surgery. The main objective of such a strict diet is to reduce liver size, all patients with a BMI of 35 or above suffer from a condition known as fatty liver and this diet that will allow the liver "shrink" enough to the extent of allowing the surgeon to work properly at the time of surgery leading to better visibility in the surgical field.


This change in the liver will be achieved without doubt if the diet is carried out to the letter, will also be reflected in less manipulation of the internal organs during the procedure and therefore a better and faster postoperative recovery and will help decrease the chances of trans or postoperative complications.


We are aware that the change of quantity and quality in foods used to go to eat only liquids is a physical and mental drastic change, but it is very important to prepare this diet to make the operation a success.


The change that represents from what you are used to have in regards of quantity and quality of food to only liquids is drastic, but it is very important to prepare yourself with this diet in order to make have a successful and uneventful surgery.


Usually, after 3 or 4 days into this diet hunger subsides more easily and in order to extend the periods without hunger we recommend ingesting high protein and/or fiber liquids , which also provide more energy.


You may develop certain side effects like headache or irritability, especially if the body is "wiping" certain chemicals that you were used to receive through food.


Some constipation may also be present. In these cases what you should do is get enough pure water to maintain good hydration. The aim is to ensure that intake is reduced to only 800-1000 calories per day and with a diet like this, it can be done.


Finally, the main reason to take this diet is to be able to eventually break old bad eating habits and achieve a definitive and long lasting solution to your weight problems and certainly we can assure you that the gastric sleeve surgery will allow you to achieve this.


Remember, our main goal as bariatric group, beyond cosmetic results (which are also valid and important for most of our patients) the most important thing for us is to help give you a 180 degree turn to your state of health for the present and future.


The gastric sleeve procedure in México is totally safe, we invite you to get a free evaluation with us and share your questions about the gastric sleeve cost in México, side effects, etc.

If you are interested in having your gastric sleeve surgery in mexico, contact us at


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Written by: Gabriel Rosales

Dr. Gabriel Rosales is a highly skilled, board certified surgeon in constant pursuit of learning the latest innovations in the weight loss surgery field to give his patients the best care possible.