Bariatric Pre & Post Operative Diets

Pre- and post-op diets are not only essential but crucial for the success of gastric sleeve surgery, a commonly performed bariatric procedure. The likelihood of achieving positive outcomes greatly increases with strict adherence to these dietary guidelines. Most complications following the surgery stem not from the surgical intervention itself, but from deviations from the prescribed diet. Failure to comply with the surgeon’s dietary instructions can lead to significant problems such as nutrient deficiencies, dehydration, and even surgical complications like leaks or strictures. Thus, understanding and following the diet plan meticulously before and after the surgery is fundamental to both recovery and long-term success. This regimen prepares the body for surgery, minimizes surgical risks, and facilitates a smoother transition to a new lifestyle of healthy eating habits post-surgery.

Pre-Operative Diet

Before having weight loss surgery, your surgeon has recommended that you follow a low sugar, reduced calorie diet for the next 14 days, it is essential you follow a special pre-operative diet for two weeks prior to having weight loss surgery. Patients will need to have a liquid diet during this time; the diet is to help shrink the liver prior to surgery. A shrunken liver during surgery gives the surgeon greater access to the exposed stomach laparoscopically, when preforming surgery and makes the surgery go easier, allowing the doctor to have more room to work around the liver.

The diet is low in fats and in carbohydrates, therefore, reducing the glycogen stores. This in returns reduces the size of the liver causing it to shrink and soften. When performing bariatric surgery the surgeon will need to lift your liver to access your stomach. Having a liver which is immobile, fatty, and heavy, will make it difficult for the surgeon to see and have access to the stomach. Following this diet you will lose weight prior to surgery, and more importantly you will reduce the size of your liver, resulting in a safer surgery.

Special Instructions
**Special Note for Patients with Diabetes
If you have diabetes and are treated with insulin or a sulphonylurea tablet (gliclazide, glibenclamide, tolbutamide, glimepiride, glipizide), you will need to adjust your insulin or medication. They will need to understand your calories will be around 800/day from the time you start this diet and medication management goal is to have less medication and not more food. For this reason please contact your Diabetes Specialist Nurse/Practice Nurse/GP/PCP before starting the preoperative diet to discuss your medication and any possible adjustments needed. It is also recommended you monitor your blood sugar closely. This diet will likely be a reduction for normal intake of carbohydrates and calories. Consult with your medical provider as needed.

**Special Note for Lactose Intolerant Patients.
If dairy products including milk give you gas, cramping, bloating or diarrhea you may be lactose intolerant. It is recommended you choose Boost Diabetic for your meal replacement choice because it is lactose free. If you choose to use a protein shake made with milk products take a Lactaid or similar lactase enzyme pill at the start of each meal containing one of these products. As you will see in the Pre-Operative diet snack choices include cottage cheese, and yogurt many lactose intolerant individuals are able to consume yogurt without experiencing gas or bloating. If you choose to eat cottage cheese it is recommended you take the lactase enzyme with your cottage cheese.


** No Chewing gum with sugar or carb sweetener, breath mints, cough syrup, hard candy or cough drops they contain high amounts of sugar.

** Stop usage of tobacco products during this pre-operative diet and during the post-operative care informational you will receive.

Bariatric Pre-Operative Diet
Food Consumption
There are no caloric limitations on the liver shrinking diet. You are able to eat as much and drink as much as you like from the list of allowable things. We do suggest reasonable limits to aid in your weight loss of a maximum of 40-50 carbohydrates daily. Typical protein intake between 70-120 grams a day, through protein shakes. It is suggested you take a multi-vitamin during your pre-op diet and during post-op. Many patients have stated that Premier Protein & Unjury as being some of the better tasting shake choices.

Here is the list of Pre-Op Diet food to follow before having your weight loss surgery. You will be following something very similar to a liquid diet.

All the water you can drink
All the natural fruit juice you can drink (make sure it has No Sugar Added on the label)
Coffee or Tea (decaf only)
Low fat creamer, Skim or 1% milk, Soy milk
Sugar-free drinks only (Crystal Light, G-2 Gatorade, Diet PowerAde, Propel, etc.)
All the broth you can eat chicken or vegetable is OK
Please drink 3 Vitamin supplements per day Any Flavor is fine (with low sugar & carbs)
Diet V-8 fusion, etc.
Sugar-free Gelatin (no fruit added)
Sugar free popsicles
Sugar-free pudding
All the plain yogurt you can eat (Greek yogurt has almost double the amount of protein per serving)
We are aware this can be a challenge for many of our patients to do for the entire period of time. If you get hungry it is okay the first week to eat 4 ounces of fish, lean turkey, chicken breast, ham, roast beef, but it must be baked, broiled, or grilled (NO FRIED FOODS). The day prior to surgery attempt to drink all clear liquids such as water, broth, clear juice, Kool-Aid (sugar free), pulp free drinks, lemonade, grape juice, apple juice, broth, etc.

The Night Before your Surgery, DO NOT EAT OR DRINK anything after Midnight 12 am and we need you on a 100% Fast that day when you arrive for surgery.

Post Operative Diet

It is important for you to make healthy food choices after your surgery to help you with weight loss and to maintain your nutritional health. A changed eating pattern is important for weight loss, to avoid stomach pains, and to prevent nutritional deficiencies.



  • To help you to achieve the maximal amount of weight loss.
  • To help prevent nutritional deficiencies and other complications.

It is important to note that lifestyle and behavioral changes are necessary to be successful with your weight loss journey.

    • Eat three meals a day and limit unnecessary snacking in-between meals. This weight loss surgery is a restrictive procedure, which means that the success of weight loss depends on what you are eating. Unhealthy snacking in-between meals (e.g. pretzels, crackers, cookies, etc.) or eating frequently may prevent successful weight loss or cause weight gain due to excess calorie intake.
    • Eat slowly and chew your food until LIQUID. Failure to do so can cause pain, nausea, vomiting, and irritate your new pouch. It is very important to chew very thorough until it is liquid. Also, remember to cut your food into small pieces before eating it. Try waiting one minute in between bites. Allow at least 30 minutes for a meal
    • Avoid concentrated sugar. Keep sugar out of the first 3 ingredients on the food label. The number of sugar grams on the label includes both added and natural sugars; therefore, it is important to read the ingredients to find out what type of sugar the food contains. Aim to keep the “sugars” down to 15 grams or less per serving to help limit “empty calories” in your diet. Avoid these simple sugars, especially if within the first 3 ingredients on food labels: sugar, dextrose, high fructose corn syrup, corn syrup, glucose, sucrose, molasses, and honey Note: Artificial sweeteners such as NutraSweet/Equal®, saccharine/Sweet & Low®, and sucralose/Splenda® are acceptable to use.
    • Limit high fat foods. Low fat is 3 grams or less per serving on a food label. Examples of high fat foods: potato chips, fried foods, fast food, bacon, sausage, hot dogs, bologna, pepperoni, cream soups, Alfredo sauce, donuts, cakes, cookies, and pastries.
    • Stop eating when you feel comfortably satisfied. Overeating can cause nausea, vomiting, and the size of your stomach to stretch. It can take 6-9 months for your new stomach size to stabilize.
    • Drink adequate fluids to prevent dehydration. Aim for 48-64 fl oz (6-8 cups) of fluid per day.
    • Sip on your beverages, no gulping!
    • Avoid carbonated beverages, beverages containing sugar and alcoholic beverages.
    • Choose sugar-free, non-carbonated drinks such as: Crystal light®, Fruit 2O®, Diet Snapple®, Propel Fitness Water, Light Minute Maid® drinks, Diet Ice Tea, etc.
    • Limit fat free milk to less than 16 ounces per day, limit 100% real fruit juice to less than 8 ounces per day (try diluting with water).



  • Wean off carbonated and caffeinated beverages before surgery to help prevent withdrawals.
  • Choose beverages with 10 calories or less per serving.
  • If plain water sits heavy and you are having problems tolerating it add a sugar-free flavoring (e.g. True Lemon®, lemon or orange slice, etc.)
  • Increase your fluid intake if any of the following signs are present: dark urine, headache, dizziness, lethargy, a white coating on the tongue.
  • AVOID eating and drinking at the same time. Avoid drinking with your meal, then wait at least 30 minutes after a meal to resume drinking.
  • Choose your food wisely, at each meal protein should be consumed first, then vegetables and fruits, then “whole” grains.
  • Exercise!
  • Aim for at least 30 minutes every day.
  • Exercise helps maintain long-term weight loss.
  • Even 5 minutes at a time, as tolerated, is a start, and increase the time and frequency as tolerated.
  • The first four weeks, the primary exercise used should be walking. After four weeks, try introducing strength exercises.
  • Always speak with your doctor if you have never exercised.
  • Protein. You need to consume at least 60-80 grams of protein per day in the form of food and/or supplements.

Protein Content of Common Foods

Meats, Poultry, and FishPortion SizeGrams of Protein
Beef/Turkey Jerky1 oz dried10-15 Grams
Beef, Pork, Poultry, Fish1 oz (2 Tbsp)7 Grams
Cheese, hard (low-fat)1 oz7 Grams
Kraft free/Healthy Choice1 oz 1 slice5 Grams
Borden fat free singles1 oz 1 slice5 Grams
Cottage cheese, Ricotta (part skim)2 Tbsp3.5 Grams
Imitation Crab Meat1 oz3 Grams
Crabmeat1 oz (2 Tbsp)6 Grams
Shrimp, Lobster1 oz6 Grams
Egg1 oz6 Grams
Baby Food Meat1 oz (2 Tbsp)4 Grams
Potted Meats/Spam Lite2 oz8.5 Grams
Hot Dog, Low-fat (average)1 oz3.5 Grams
Tuna Fish1 oz7 Grams

Legumes and Nuts

Legumes and NutsPortion SizeGrams of Protein
Almonds1 oz dried6 Grams
Cashews1 oz4 Grams
Lentils½ cup cooked9 Grams
Lima Beans½ cup cooked7 Grams
Peanut butter2 Tbsp7 Grams
Red kidney beans½ cup cooked8 Grams
Soy beans½ cup cooked14 Grams
Tofu1 slice5 Grams
Refried beans½ cup6 Grams
Sunflower seeds1 oz5 Grams
Chili with beansdrained ½ cup10 Grams

Milk and Dairy

Milk and DairyPortion SizeGrams of Protein
Milk, skim, 1%, or lactaid8 oz8 Grams
Soy milk8 oz7 Grams
Yogurt, fat free, no sugar added6 oz8 Grams
Greek Style Yogurt, plain, nonfat5 oz13 Grams
Sugar free pudding, made with milk½ cup4 Grams

Protein Supplements

There are many brands of supplements available (ready-to-drink or powders). Some examples;

  • Look for drinks made with Whey Protein Isolate (this is absorbed well), vs. whey protein concentrate, which has lactose, or milk sugar Strive for a protein with at least 20 grams of protein per serving Mix with skim or 1% milk for an additional 8 grams of protein per serving Aim for a product with less than 3 grams of sugar per serving. Avoid and/or limit protein collagen-based products (incomplete form of protein that is missing tryptophan, an important building block of protein)
  • Examples: Ready to drink – Atkins®, E.A.S. Myoplex Carb Sense®, Zero Carb Isopure® Powders – Designer®, Unjury®, Nectar®, Premier protein®

Vitamin and mineral supplements

  • You are required to take supplement for the rest of your life to prevent deficiencies.
  • Multivitamin; One chewable or liquid multivitamin with minerals per day. Take with food. Examples: Centrum Chewables®, Flintstone Complete®
  • Calcium; 1500 mg of calcium citrate per day (take one chewable 3 times daily) Maximum of 600 mg at one time for absorption Must contain vitamin D (at least 200 IU) Examples: Twinlab® chewable calcium wafers (2 tab, 3x a day), Citracal® plus D (2 tabs, 3x a day), Solaray Calcium plus D and Mag (2 wafers, 3 times a day)

SAMPLE Table for Taking Your Supplements

Multivitamin (NOT with dairy)
Lunch 500-600 mgs
Snack 500-600 mgs
Dinner 500-600 mgs

FAQs of The Pre & Post op diets

  1. What is the purpose of the pre-op diet for gastric sleeve surgery?

    • Answer: The pre-op diet helps reduce liver size and body fat, making the surgery safer and easier for the surgeon to perform.
  2. How long does the pre-op diet last?

    • Answer: Typically, the pre-op diet lasts between 2 to 3 weeks, depending on the patient’s BMI and surgeon’s recommendation.
  3. What foods are included in the pre-op diet?

    • Answer: The diet mainly includes protein shakes, low-calorie vegetables, and lean proteins, and is low in carbohydrates and fats.
  4. Can I drink coffee during the pre-op diet?

    • Answer: Yes, but it should be black coffee with no sugar or cream. Decaffeinated is preferred to reduce any potential issues with dehydration.
  5. What is the goal of the post-op diet after gastric sleeve surgery?

    • Answer: The post-op diet aims to promote healing, provide adequate nutrition, and adjust to the smaller stomach capacity.
  6. What are the stages of the post-op diet?

    • Answer: The diet typically progresses through several stages, starting with clear liquids, then pureed foods, followed by soft foods, and finally regular, but healthier, foods.
  7. How long does each stage of the post-op diet last?

    • Answer: Each stage generally lasts about 1-2 weeks, but this can vary based on individual healing and tolerance.
  8. Can I eat solid foods during the first month after surgery?

    • Answer: No, solid foods are reintroduced gradually to avoid stressing the new stomach structure and to promote healing.
  9. What are examples of pureed foods I can eat?

    • Answer: Pureed chicken, fish, cottage cheese, soft fruits, and cooked vegetables are suitable options.
  10. Is it normal to experience nausea during the post-op diet?

    • Answer: Yes, nausea can occur as you adjust to the new diet and stomach capacity, but if persistent, consult your doctor.
  11. How much protein should I consume daily after surgery?

    • Answer: The goal is typically 60-80 grams of protein per day, but your surgeon or dietitian may adjust this based on your specific needs.
  12. Why is hydration important after gastric sleeve surgery?

    • Answer: Proper hydration is crucial to prevent dehydration, constipation, and kidney stones, and to aid overall recovery.
  13. How much water should I drink daily after surgery?

    • Answer: Aim for at least 64 ounces (about 2 liters) of fluids per day, unless otherwise directed by your healthcare provider.
  14. Can I drink alcohol after gastric sleeve surgery?

    • Answer: Alcohol should be avoided, especially during the early recovery phase, as it is high in calories and can irritate the stomach lining.
  15. What vitamins will I need to take post-surgery?

    • Answer: Most patients need to take a multivitamin, calcium with Vitamin D, iron, and Vitamin B12 supplements, as prescribed by their healthcare provider.
  16. When can I start exercising after gastric sleeve surgery?

    • Answer: Light activities, like walking, can start almost immediately, but more strenuous exercise should be avoided until 4-6 weeks post-op, or as recommended by your surgeon.
  17. How do I prevent dumping syndrome?

    • Answer: Avoid sugary and high-fat foods, eat small, frequent meals, and chew food thoroughly to help prevent dumping syndrome.
  18. What are the signs of food intolerance after surgery?

    • Answer: Symptoms of food intolerance may include nausea, vomiting, diarrhea, bloating, and abdominal pain after eating certain foods.
  19. Can I return to a normal diet eventually?

    • Answer: Yes, but your new “normal” will include smaller portions, healthier food choices, and possibly some permanent restrictions on very high fiber or fatty foods.
  20. What happens if I overeat after having a gastric sleeve?

    • Answer: Overeating can stretch your stomach, cause pain, vomiting, and other complications, and undermine the effectiveness of the surgery.