Post Gastric Bypass Diet

The gastric bypass diet is designed for people who are recovering from gastric bypass surgery to help them heal and change their eating habits. Your doctor or a registered dietitian can help you with a gastric bypass diet by guiding meal planning. A gastric bypass diet specifies what type and how much food you can eat at each meal. Closely following your gastric bypass diet can help you lose weight safely.


The gastric bypass diet has several purposes:

  • To allow the staple line in your stomach to heal without being stretched by the food you eat
  • To get you accustomed to eating the smaller amounts of food that can be digested comfortably and safely in your smaller stomach
  • To help you lose weight and avoid gaining excess weight
  • To avoid side effects and complications

General guidelines

  • Eat balanced meals with small portions.
  • Follow a diet low in calories, fats and sweets.
  • Keep a daily record of your food portions and of your calorie and protein intake.
  • Eat slowly and chew small bites of food thoroughly.
  • Avoid rice, bread, raw vegetables and fresh fruits, as well as meats that are not easily chewable, such as pork and steak. Ground meats are usually better tolerated.
  • Do not use straws, drink carbonated beverages or chew ice. They can introduce air into your pouch and cause discomfort.
  • Avoid sugar, sugar-containing foods and beverages, concentrated sweets and fruit juices.
  • For the first two months following surgery, your calorie intake should be between 300 and 600 calories a day, with a focus on thin and thicker liquids.
  • Daily caloric intake should not exceed 1,000 calories.


  • Drink extra water and low-calorie or calorie-free fluids between meals to avoid dehydration. All liquids should be caffeine-free.
  • Sip about 1 cup of fluid between each small meal, six to eight times a day.
  • We recommend drinking at least 2 liters (64 ounces or 8 cups) of fluids a day. You will gradually be able to meet this target.
  • We strongly warn against drinking any alcoholic beverages. After surgery, alcohol is absorbed into your system much more quickly than before, making its sedative and mood-altering effects more difficult to predict and control.


Preserve muscle tissue by eating foods rich in protein. High-protein foods include eggs, meats, fish, seafood, tuna, poultry, soy milk, tofu, cottage cheese, yogurt and other milk products. Your goal should be a minimum of 65 to 75 grams of protein a day. Don’t worry if you can’t reach this goal in the first few months after surgery


You must take the following supplements on a daily basis to prevent nutrient deficiencies. Please remember that all pills must be crushed or cut into six to eight small pieces. You are not able to absorb whole pills as well as before surgery, and it can be difficult for the pills to pass through your new anatomy.

  • Multivitamins: Take a high-potency daily chewable multivitamin and mineral supplement that contains a minimum of 18 mg of iron, 400 mcg of folic acid, selenium, copper and zinc. Brands that contain this formula include Trader Joe’s and Centrum Adult chewable multivitamins. Take two tablets daily for at least three months after your surgery, and then one tablet daily for life.
  • Calcium supplement: Take 1,200 to 2,000 mg of calcium daily to prevent calcium deficiency and bone disease. To enhance absorption, take the calcium in two to three divided doses throughout the day: for example, a 500 to 600 mg supplement taken three times a day. Calcium citrate is the preferred form of calcium.
  • Vitamin D supplement: Take a total of 800 to 1,000 International Units (IUs) of vitamin D each day. This total amount should be taken in divided doses of 400 to 500 IUs twice a day. Vitamin D should be taken with your calcium supplement. If you prefer, you can take a combination calcium-vitamin D supplement to avoid taking multiple pills, so long as it contains the proper dosages.
  • Vitamin B12 supplement: Take 500 mcg of vitamin B daily. It can be taken as a tablet, or in sublingual forms placed under the tongue.
  • Other supplements: Some patients need additional folic acid or iron supplements, particularly women who are still menstruating. Your dietitian will discuss this with you.

Diet details

Diet recommendations after gastric bypass surgery or other weight-loss surgery vary depending on the type of surgery, where the surgery is performed according to your individual situation. Most commonly, the gastric bypass diet has four phases to help you ease back into eating solid foods. How quickly you move from one step to the next depends on how fast your body heals and adjusts to the change in eating patterns. You can usually start eating regular foods with a firmer texture about three months after surgery. After gastric bypass or other weight-loss surgery, you must pay extra attention to signs that you feel hungry or full. You may develop some food intolerances or aversions.

Phase 1: Liquid diet

You won’t be allowed to eat for one to two days after gastric bypass surgery so that your stomach can start to heal. After that, while you’re still in the hospital, you start a diet of liquids and semisolid foods to see how you tolerate foods after surgery. Foods you may be able to have in phase 1 of the gastric bypass diet include:

  • Broth
  • Unsweetened juice
  • Milk
  • Strained cream soup
  • Sugar-free gelatin

During phase 1, sip fluids slowly and drink only 2 to 3 ounces (59 to 89 milliliters, or mL) at a time. Don’t drink carbonated or caffeinated beverages and don’t eat and drink at the same time. Wait about 30 minutes after a meal to drink anything.

Phase 2: Pureed foods

Once you’re able to tolerate liquid foods for a few days, you can begin to eat pureed (mashed up) foods. During this two- to four-week-long phase, you can only eat foods that have the consistency of a smooth paste or a thick liquid, without any solid pieces of food in the mixture.

To puree your foods, choose solid foods that will blend well, such as:

  • Lean ground meats
  • Beans
  • Fish
  • Egg whites
  • Yogurt
  • Soft fruits and vegetables
  • Cottage cheese

Blend the solid food with a liquid, such as:

  • Water
  • Fat-free milk
  • Juice with no sugar added
  • Broth
  • Fat-free gravy

Keep in mind that your digestive system might still be sensitive to spicy foods or dairy products. If you’d like to eat these foods during this phase, add them into your diet slowly and in small amounts.

Phase 3: Soft, solid foods

With your doctor’s OK, after a few weeks of pureed foods, you can add soft, solid foods to your diet. If you can mash your food with a fork, it’s soft enough to include in this phase of your diet.

During this phase, your diet can include:

  • Ground or finely diced meat
  • Canned or soft, fresh fruit
  • Cooked vegetables

You usually eat soft foods for eight weeks before eating foods of regular consistency with firmer texture, as recommended by your dietitian or doctor.

Phase 4: Solid foods

After about eight weeks on the gastric bypass diet, you can gradually return to eating firmer foods. You may find that you still have difficulty eating spicier foods or foods with crunchy textures. Start slowly with regular foods to see what foods you can tolerate.

Avoid these foods. Even at this stage after surgery, avoid these foods:

  • Nuts and seeds
  • Popcorn
  • Dried fruits
  • Sodas and carbonated beverages
  • Granola
  • Stringy or fibrous vegetables, such as celery, broccoli, corn or cabbage
  • Tough meats or meats with gristle
  • Breads

These foods are discouraged because they typically aren’t well tolerated in the weeks after surgery and might cause gastrointestinal symptoms. Over time, you may be able to try some of these foods again, with the guidance of your doctor.

A return to normal:

Three to four months after weight-loss surgery, you may be able to start returning to a normal healthy diet, depending on your situation and any foods you may not be able to tolerate. It’s possible that foods that initially irritated your stomach after surgery may become more tolerable as your stomach continues to heal.

Throughout the phases:

To ensure that you get enough vitamins and minerals and keep your weight-loss goals on track, at each phase of the gastric bypass diet, you should:

  • Keep meals small: During the diet progression, you should eat several small meals a day and sip liquids slowly throughout the day (not with meals). You might first start with six small meals a day, then move to four meals and finally, when following a regular diet, decrease to three meals a day. Each meal should include about a half-cup to a cup of food. Make sure you eat only the recommended amounts and stop eating before you feel full.
  • Take recommended vitamin and mineral supplements: Because a portion of your small intestine is bypassed after surgery, your body won’t be able to absorb enough nutrients from your food. You’ll need to take multivitamin supplements every day for the rest of your life, so talk to your doctor about what type of multivitamin might be right for you, and whether you might need to take additional supplements, such as calcium.
  • Drink liquids between meals: Drinking liquids with your meals can cause pain, nausea and vomiting as well as dumping syndrome. Also, drinking too much liquid at or around mealtime can leave you feeling overly full and prevent you from eating enough nutrient-rich foods. Expect to drink at least 6 to 8 cups (48 to 64 ounces or 1.4 to 1.9 liters) of fluids a day to prevent dehydration.
  • Eat and drink slowly: Eating or drinking too quickly may cause dumping syndrome; when foods and liquids enter your small intestine rapidly and in larger amounts than normal, causing nausea, vomiting, dizziness, sweating and eventually diarrhea. To prevent dumping syndrome, choose foods and liquids low in fat and sugar, eat and drink slowly, and wait 30 to 45 minutes before or after each meal to drink liquids. Take at least 30 minutes to eat your meals and 30 to 60 minutes to drink 1 cup (237 milliliters) of liquid. Avoid foods high in fat and sugar, such as non-diet soda, candy, candy bars and ice cream.
  • Chew food thoroughly: The new opening that leads from your stomach into your intestine is very small, and larger pieces of food can block the opening. Blockages prevent food from leaving your stomach and can cause vomiting, nausea and abdominal pain. Take small bites of food and chew them to a pureed consistency before swallowing. If you can’t chew the food thoroughly, don’t swallow it.
  • Try new foods one at a time: After surgery, certain foods may cause nausea, pain and vomiting or may block the opening of the stomach. The ability to tolerate foods varies from person to person. Try one new food at a time and chew thoroughly before swallowing. If a food causes discomfort, don’t eat it. As time passes, you may be able to eat this food. Foods and liquids that commonly cause discomfort include meat, bread, pasta, rice, raw vegetables, milk and carbonated beverages. Food textures not tolerated well include dry, sticky or stringy foods.
  • Focus on high-protein foods: Immediately after your surgery, eating high-protein foods can help heal your wounds, regrow muscle and skin, and prevent hair loss. High-protein, low-fat choices remain a good long-term diet option after your surgery, as well.
  • Avoid foods that are high in fat and sugar: After your surgery, it may be difficult for your digestive system to tolerate foods that are high in fat or added sugars. Avoid foods that are fried and look for sugar-free options of soft drinks and dairy products.


Gastric bypass and other bariatric surgery can result in long-term weight loss. The amount of weight you lose depends on your type of weight-loss surgery and the changes you make in your lifestyle habits. It may be possible to lose half, or even more, of your excess weight within two years. The gastric bypass diet can help you recover from surgery and return to enjoying many of the healthy foods before surgery. And remember that if you return to unhealthy eating habits after weight-loss surgery, you may not lose all of your excess weight, or you can eventually regain any weight that you do lose.


The greatest risks of the gastric bypass diet come from not following the diet properly. If you eat too much or eat food that you shouldn’t, you could have complications. These include:

  • Dumping syndrome: This complication occurs most often after eating foods high in sugar or fat. These foods travel quickly through your stomach pouch and “dump” into your intestine. Dumping syndrome can cause nausea, vomiting, dizziness, sweating and eventually diarrhea.
  • Dehydration: Because you’re not supposed to drink fluids with your meals, some people become dehydrated. You can prevent dehydration by sipping 48 to 64 ounces (1.4 to 1.9 liters) of water or other low-calorie beverages throughout the day.
  • Nausea and vomiting: If you eat too much, eat too fast or don’t chew your food adequately, you may become nauseated or vomit after meals.
  • Constipation: If you don’t follow a regular schedule for eating your meals, don’t eat enough fiber or don’t exercise, you may become constipated.
  • Blocked opening of your stomach pouch: It’s possible for food to become lodged at the opening of your stomach pouch, even if you carefully follow the diet. Signs and symptoms of a blocked stomach opening include ongoing nausea, vomiting and abdominal pain. Call your doctor if you have these symptoms for more than two days.
  • Weight gain or failure to lose weight: If you continue to gain weight or fail to lose weight on the gastric bypass diet, it’s possible you could be eating too many calories. Talk to your doctor or dietitian about changes you can make to your diet.


Changing your eating habits will be important if the operation is to be a success. Although your smaller upper stomach and smaller opening that releases the food and liquid into the intestine will help, several of the following problems may be encountered once eating is resumed after surgery.

Managing liquids

  • Fluids are needed to replace normal water loss and to prevent dehydration. We recommend that you try to drink 2 liters (64 oz.) of liquid (mostly water and non-caffeinated beverages) every day.
  • Avoid liquids with meals, saving room for solid foods, and preventing the “washing” of food from the stomach. Stop drinking fluids at least 30 minutes before a meal, and wait at least 30 minutes after the meal, to allow for digestion of food. This will make a profound impact on your feeling of satiety (satisfaction or fullness) after eating.
  • When drinking liquids, sip them slowly. If liquids are gulped too quickly, abdominal cramping, discomfort, and/or vomiting may occur.
  • Avoid carbonated beverages and drinking from a straw for approximately 6 weeks after surgery. Doing this can help you to avoid excess gas and pressure.

Nausea, vomiting, bloating and/or heartburn

Nausea, vomiting, bloating and/or heartburn can occur from any of the following:

  • Eating and drinking too quickly
  • Not chewing food well enough
  • Drinking cold fluids
  • Eating too much (quantity)
  • Eating rich or sweet foods, fried, or high-fat foods
  • Eating gas-producing foods or drinking carbonated beverages

Dumping syndrome

Dumping syndrome can be a feeling of abdominal fullness, weakness, warmth, rapid pulse, cold sweats, nausea, possible vomiting, and possible diarrhea. This happens whenever foods and beverages that are high in sugar or grease are consumed and ‘dumped’ into the bowel quickly. To avoid dumping syndrome, avoid concentrated sweets (ice cream, milkshakes, candy, pies, cookies, cake, sugar, syrup, honey, jelly, pastries, regular soda, fruit juices, barbecue sauces, etc.). You may only be able to tolerate a teaspoonful of these items at a time, if any at all. This may also occur after eating greasy foods such as fried chicken or French fries.

Blockage of the stoma

The new opening created by the surgery is smaller than the original opening that released food from the stomach into the intestine. This new opening may become blocked when food has not been thoroughly chewed, which can result in abdominal pain or vomiting.

If you become unable to tolerate water within the first month after surgery, call us immediately. The sooner we learn of this problem, the more likely we will be able to treat it without surgery.

To prevent blockage from occurring:

  • Avoid eating high fiber foods, such as raw fruits and vegetables, and starchy foods for the first 6 weeks after surgery. After 6 weeks’ time, be sure to chew high fiber foods very thoroughly.
  • Chew all foods to the consistency of mush before swallowing.
  • Be careful when chewing gum; if accidentally swallowed it can cause a blockage.
  • Use chewable or liquid multivitamins.


The purpose of bariatric surgery is to create a smaller stomach so that it is unable to hold the large volumes of food it had held previously. Constant overeating can stretch your stomach pouch. Remember that your pouch is only 1 ounce (the size of your thumb). Meals should be about 3-4 ounces (1/2 cup). The more solid the food, the less you will be able to eat. You may be able to eat 4 ounces of applesauce, but only 2 ounces of beef. Even though the amount is smaller, choose the beef because you need the protein.

To prevent stretching the pouch:

  • Eat only three small meals each day, and measure your food before you eat to prevent overfilling the stomach.
  • Eat slowly so that the nerve receptors in your stomach area can relay the message to your brain that your stomach is full. It takes approximately 15-20 minutes for the message of fullness to reach the brain. Take time between bites of food and stop eating as soon as fullness is experienced.
  • Recognize when you are full, which can feel like pain or pressure in the center just below your rib cage, nausea, or a pain in your shoulder or upper chest. The next step is to stop eating when you feel full.
  • Constant nibbling/grazing/snacking may not stretch your stomach pouch, but it is a common bad food behavior among people who do not meet their weight loss goals and/or regain significant amounts of weight after surgery.

Under nutrition

Total food consumption is reduced after surgery, and therefore, intake may be nutritionally inadequate. To compensate for reduced nutrient intake:

  • Consume nutrient-dense foods daily, including a variety of lean meats, low-fat dairy, fruits and vegetables, and high fiber breads and cereals. Look for breads that have at least 3g of fiber per slice, and cereals that have at least 5g of fiber per cup. Avoid empty calorie foods, including soda pop, Kool-Aid, chips, pretzels, popcorn, candy, pastries, sweets, and rice cakes. Avoid foods that are breaded and fried.
  • Consume adequate high biological value protein foods each day. See the section on protein for examples of such foods.
  • Take the recommended vitamins (multivitamins, calcium, vitamin D, iron, and vitamin B12 supplements) every day. THIS IS IMPORTANT! Refer to the vitamin section of this handout.

Food intolerance

Food intolerance varies widely and one individual may tolerate a food that disagrees with another person. Therefore, it is important to try a variety of foods. Each individual must try new foods carefully to test his or her reactions after surgery.

The following foods may be difficult to eat, especially for the first few months:

  • Tough meats: dry, gristly meats may be difficult to digest. Meats (chicken, steak, and burger) should be moist and cut into very small pieces about the size of a pencil eraser. Go slow.
  • Bread: Fresh, doughy bread can form a ball and “gum up” the opening from the stomach.
  • Pasta: Pasta may form a paste and be more difficult to pass.
  • Seeds and skins of fruits and vegetables, dried fruit, fibrous vegetables like corn, asparagus, and celery
  • Nuts and peanut butter

Do not be discouraged if a certain food does not agree with you once. Wait a few weeks and try it again. Your stomach might just not have been ready for the food yet.

  • universite de montreal
  • American Society for Metabolic and Bariatric Surgery
  • mount sinai
  • Prince Mohamed bin Abdulaziz Hospital
  • International Federation for the Surgery of Obesity and Metabolic Disorders
  • King Khalid University Hospital
  • American Association of Bariatric Counselors
  • Society of American Gastrointestinal and Endoscopic Surgeons
  • mc gill
  • Society for Surgery of the Alimentary Tract
  • surgery for obesity and related diseases
  • The International College of Surgeons (ICS)
  • juniper online journal of case studies
  • Obesity Medicine
  • journal of universal surgery
  • american journal of innovative research & applied sciences
  • asian council of science editors
  • medcrave
  • insight knowledge
  • American College of Surgeons
  • Specialized Medical Center
  • Saudi German Hospitals