Post-operative weight loss surgery diet - Bariatric Diet Guidelines

Post-Operative Weight Loss Surgery Diet

We will cover the post-operative diet that applies to gastric surgery patients, including Vertical Sleeve Gastrectomy (VSG) and RNY Gastric Bypass (RGB). Post-op dietary guidelines are essential to avoid complications and ensure successful weight loss.

Why is the Post-op Diet Necessary?

The dietary restriction is required after surgery since there is a lot of adjustment done resulting in swelling and inflammation caused by both sleeve and bypass. In sleeve gastrectomy, the stomach is reduced and a narrow channel is created where food travels through.

Gastric Bypass

Gastric bypass, a Gastrojejunostomy is created (anastomosis between the stomach and the proximal loop of the jejunum) with a tiny pouch as a new reservoir to hold food. These changes mandate the patient to start from liquids just following the surgery, to soft mushy food, and slowly progress to solid food.

Gastric Sleeve

For gastric sleeve patients, it is absolutely crucial to go through the post-op phases very slowly and listen to your body for any possible safety issues, besides any of the more common comfort issues. As for gastric bypass, complying with the post-op diet is more a matter of comfort than safety.

Bariatric Vitamins and Supplements

At least in the first year after surgery, it is essential to take specific vitamins made for bariatric patients and to take them consistently. Do not just take any over-the-counter vitamin, like Centrum multivitamins.

If you compare the content (iron, B, other minerals) of the bariatric multivitamins and regular multivitamins, you see that the bariatric vitamin has 2 to 3 times more of the essential ingredients and nutrients. The bariatric multivitamins are chewable and tolerable; as a matter of fact, they can be taken even a week after surgery. Some people may not do well with bariatric vitamins and they can crush them in their smoothie.

Vitamins are a superficial replacement of those minerals and substances we need on a daily basis. It is required to get enough of the other compounds, called Phytonutrients, needed in our diet.

Phytonutrients are found in fruits, vegetables, beans, nuts, and seeds. Patients have to make sure to take bariatric multivitamins as well as Phytonutrients, in the form of these plants, in their daily diet.

Side Effects of Long-Term Nutrient Deficiencies


  • Anemias – Group of different blood disorders caused by inadequate intake of absorption of iron, B12, folate, copper, or zinc.
  • Bone Disorders – Various bone disorders, including weak, porous, and soft bone. It is caused by a lack of D, calcium, K, magnesium, essential fatty acids, b-vitamins, … Remember vitamin D is needed for calcium absorption.
  • Neurological Disorders – The body needs a constant supply of vitamin B1 (thiamin) and thiamin deficiency causes confusion and paralysis.
  • Muscle Health – Dietary protein feeds our muscles and inadequate intake of it causes weakness and unfavorable body composition.

Two Basic Phases of Post-Op Diet

The post-op period can be divided into two phases:

Phase One (Hydration & Protein)

Phase one starts right after surgery with clear liquid and typically lasts 1-2 weeks:

  • water
  • chicken and vegetable broth
  • sugar-free popsicles
  • regular tea, herbal tea, green tea
  • crystal light
  • no juice, no sugar

Once you tolerate 40 to 64 oz of fluid per day, you can add protein shakes and other pureed items such as blended soup, applesauce, and greek yogurt (You should have a goal of at least 60 grams of protein per day). See green protein shake recipe.

Keep in mind that commercial protein shakes are artificial and need to be phased out as you progress into your post-op diet.

Phase Two (3 to 6 weeks)

After you are able to hydrate and keep protein down, you can slowly advance your diet going through the following phase:

  • Soft dairy
    • Plain, low fat, organic yogurt blended with fruit
    • Cottage cheese
    • Applesauce w/o added sugar
  • Cooked Vegetables
    • Carrots
    • Sweet potatoes
    • Asparagus
    • Broccoli
    • Cauliflower
  • Eggs & Beans
    • Poached (most tolerable), fried (small amount of butter), scrambled, hard-boiled
    • Beans are the most important part of after surgery diet – bean soups, vegetarian refried beans
  • Fish & Nuts
    • Baked flakey fish (Tilapia, Cod, Perch) – avoid seafood at first
    • Raw/natural nuts are an excellent source of protein – do not start with nut butter (peanut butter, etc)
  • Chicken & Poultry
    • If you can tolerate chicken, you can eat anything. Dark meat first
    • No cuts of beef and alcohol for 3 months after surgery

Post-Operative Eating Tips

Try to avoid drinking from a straw at first as it can incorporate air into your stomach and cause discomfort, however, straws are okay to use once you have become mindful of how much and how quickly you can drink without causing issues. Carbonated water (Perrier, Pellegrino, …) is okay to drink without stretching your stomach, however, can also cause discomfort Just listen to your body – it will tell you when you have taken in too much or if your body is not ready for it yet.


It happens to about one-third of patients in the first month after surgery. After surgery, patients commonly vomit foam and spit but usually not large amounts of food. Vomiting for patients after surgery is not a big concern. It is a concern in patients, especially bypass if they vomit bile. If you vomit, that means you messed up. Gastric sleeve perforation can happen within two months after surgery, caused by eating a too big piece of food. Sleeve patients are critical to go slowly through the post-op diet for their safety, whereas for bypass patients it is a matter of comfort.


Dehydration is something you need to be concerned about. Patients should take a bottle of water with them and take a slow and steady sip every 5 minutes (40 oz of water per day minimum). Men tend to be guzzlers, so sipping slowly can be even more of a challenge. As a result, they are more prone to dehydration.

What is Next?

After going through phase I and II, you need to:

  • Add more vegetables (1 lb a day) as you can tolerate chicken and more food.
  • The rules for bariatric surgery patients after 6 months is pretty much like the individuals trying to maintain a healthy lifestyle (see How much do I lose after surgery?).
  • Phase-out metabolic protein shakes.
  • Eat lots of good calories (plant-based calories) and less bad calories (processed food, grains, bread, etc.)
  • Develop new hobbies, interests to substitute for food as a primary source of pleasure. Exercise & stay active and spend time with friends and family.


Eating After Bariatric Surgery

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