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After Gastric Bypass: Nutrition Guidelines

After gastric bypass surgery, you will need to learn a new way to eat and drink. Your new stomach is much smaller than it was before. And it may have a small opening at the bottom called a stoma. Your bariatric surgeon may call it the gastrojejunostomy. This can become blocked by food if you're not careful. To protect your new stomach and get the results you want, you must:

  • Eat very small meals.

  • Eat slowly.

  • Eat softer foods.

  • Chew food well.

  • Don't eat food and drink liquids at the same time.

  • Take your vitamins and supplements regularly, as directed by your healthcare provider.  

It's important to follow the eating plan that has been laid out for you. The surgery was only the first step. Success in losing weight depends on the choices you make after surgery.

After surgery

After surgery, you will likely start with a liquid diet, slowly move to a full liquid diet, and then onto pureed or soft solid foods over the next several weeks. Follow your bariatric surgery team's instructions for what liquids and soft foods are best. After this time, you can start to bring other foods back into your diet, following the guidelines from your bariatric surgery team and dietitian.

Planning meals

After surgery, your stomach can only hold 2 to 4 tablespoons of food or drink. After about a year, it will expand to hold up to 16 tablespoons of food or drink. Because of its small size, you will need to eat and drink much less at any 1 meal than you did before surgery. You will also need to plan your meals carefully. The foods you choose should be healthy and nutritious. Work with a dietitian to learn how to eat and the best foods to choose. Follow the eating plan you are given. Below are some general guidelines.

How much to eat

Closeup of tablespoon measuring out cottage cheese.
Your new stomach holds only a small amount of food now. You will need to measure your food before eating.

Suggestions for how much to eat include the following: 

  • Eat about 4 to 6 small meals per day, following your bariatric dietitian's recommendations. 

  • Expect to follow your planned, scheduled diet for almost 2 months. When you are eating a more normal diet, stick with the recommended foods. Use a small plate. Eat slowly and chew your food well. Stop eating when you are satisfied, and don't keep eating until you feel a full feeling. You can stretch the stomach pouch if you do that. 

What to choose

Suggestions for what to choose include the following: 

  • Try to eat the right amount of protein (see “Get enough protein” below).

  • Eat fruits and vegetables if they don’t cause problems. Remove skins. Cook vegetables to make them easier to digest. Chew them well.

  • Choose whole-grain foods or add dietary fiber to your meals.

What to pass up

Suggestions for what to choose include the following: 

  • Don't have sugary foods and drinks. They can cause dumping syndrome (see Prevent dumping syndrome below). They can also slow your weight loss or cause weight gain.

  • Limit oils and fats. This includes fried foods. Too much fat can cause nausea. It can also slow your weight loss. It may even cause weight gain.

  • Don't have alcohol. It has calories, but no nutrients, and can slow your weight loss.

  • Don't smoke. Smoking is a well-known cause of ulcers at the bottom of the stomach pouch after a gastric bypass.

  • Don't take NSAIDs on a regular basis. NSAIDs are medicines, such as ibuprofen, aspirin, or naproxen. They could cause ulcers at the bottom of the stomach pouch. Check with your healthcare provider before taking any NSAIDs.

How to eat

After surgery, you will need to be careful when you eat. Your stomach is very small and can only hold a small amount of food. Follow these guidelines for eating meals:

  • Don't drink anything during a meal. Wait 30 to 45 minutes after a meal to drink again.

  • Take small bites. Chew your food well before swallowing it. If you can’t chew something completely, don't swallow it. Spit it out. This will help prevent the stoma from being blocked.

  • Eat slowly. Allow 20 to 30 minutes for a meal.

  • Stop eating when you feel full. Don't eat too fast or too much. This can cause nausea and vomiting. It may also cause pain under your breastbone.

  • Don't snack between meals. Follow your diet plan. Snacking can limit your weight loss and even cause weight gain.

Preventing complications

Certain problems can happen after gastric bypass surgery. These include dehydration, malnutrition, and dumping syndrome. You will need to eat and drink carefully to prevent these. Read below to learn what you can do.

Keep a daily food and drink log

Keep a record of everything you eat, even condiments, such as ketchup and relish. Write down all drinks, including water. This will help you keep track of what and how much you are consuming.

Stay hydrated

Not drinking enough fluids can lead to dehydration. Symptoms include feeling very thirsty, having dark yellow urine, or urinating very little. The new stomach can only hold a small amount of liquid at one time. So it's important to sip drinks throughout the day. Drink at least 6 to 8 cups (1 cup is 8 ounces) of sugar-free liquids every day. Drink slowly. Don't use straws or drink out of bottles, because this may cause painful gas. Stay away from carbonated drinks for the first few months, as they will also cause gas. Also, don't drink during meals. This can lead to food not being digested correctly.

Get enough protein

Protein is a very important part of your new diet. It makes you feel full and keeps your body working normally. After surgery, your surgical team may ask you to take protein shakes every day. You will need to eat low-fat, high-protein foods with each meal. You should work your way up to 60 to 100 grams of protein per day. If you eat meat, make sure it is not tough or full of fat or gristle. Chopped meat is often a better tolerated choice. If you can’t chew the meat thoroughly, don’t swallow the food. It can block your stoma. Stay away from high-fat protein foods, such as sausage, bacon, hot dogs, and high-fat hamburger meat. Choose low-fat, high-protein foods, such as:

  • Chicken and turkey (white meat)

  • Fish and shellfish (not breaded or fried)

  • Eggs, egg whites, and egg substitutes

  • Low-fat and fat-free dairy products (milk, yogurt, cottage cheese)

  • Soy milk and tofu

  • Tuna fish and canned salmon 

  • Peanut butter 

Beans, lentils, vegetables, and nuts also contain protein. However, they do not have all the amino acids that animal protein has. You can eat these foods, but you should have them in addition to other animal proteins, such as those listed above. If you have trouble meeting your daily protein needs, you may need to take a protein supplement. Make sure that the protein supplement has only protein and doesn't contain sugar (or lactose, if you are lactose intolerant). 

Not getting enough protein can lead to protein malnutrition. Symptoms of inadequate protein (and caloric) intake include excessive hair loss, dry skin, fatigue, and always feeling cold when others are not cold. Some of these symptoms are common after gastric bypass. You can minimize them by concentrating on protein intake. These symptoms should resolve by 4 to 6 months after the operation. 

Reintroduce foods slowly

After surgery, some foods are more likely to cause pain, nausea, vomiting, or blockage. These include meats, fruits, vegetables, breads, pasta, and rice. Try to add these back into your diet 1 at a time. Chew thoroughly. If you can’t tolerate a food, try it again in 1 to 2 weeks. Also, be careful with dairy foods. After surgery, these may give you cramps, bloating, or diarrhea. This is because you may have problems digesting lactose after surgery. If necessary, try lactose-free dairy products. Check with your healthcare provider about using lactase pills with dairy foods. This can be cheaper than buying lactose-free milk.

Prevent dumping syndrome

Dumping syndrome is a condition that can happen after gastric bypass surgery. It's related to the rapid entry or "dumping" of high-sugar meals into the intestine from the stomach pouch. It can happen 10 to 30 minutes after eating sugary foods or as late as 2 to 3 hours after eating. It can also happen after eating too quickly or too much at once. Symptoms may include intestinal cramps, nausea, vomiting, diarrhea, fast heart rate, dizziness, flushing, and sweating. The symptoms usually pass in 15 to 30 minutes. Your symptoms may go away faster if you sip 1 cup of water. You may want to rest afterward. In rare instances, you may have additional symptoms a few hours later, including low blood sugar. You may feel shaky and anxious.

Sugar is the most common cause for dumping. You can help prevent dumping syndrome by keeping your diet low in sugar. A low-sugar diet means staying away from:

  • Sugary foods, such as candy, chocolate, sweetened gum, sweetened yogurt (including frozen yogurt), sugary cereals, sweet baked goods, ice cream, and dried preserved fruit

  • Sugary drinks, such as nondiet soda, fruit juice, and coffee and tea with sugar or flavored syrups

  • Sugary condiments, such as jam, honey, and syrup

Read food and drink labels to see if they contain sugar. Look for sugars, sweeteners, syrups, cane juice, agave, maltodextrin, and words ending in –ose. You can use artificial sweeteners as substitute for sugar. These include aspartame, saccharine, stevia, and sucralose.

Take vitamin and mineral supplements

After bariatric surgery, your body will not be able to absorb all the vitamins and minerals it needs through food. Symptoms of low amounts of vitamins and minerals in your body include anemia (low blood count), sores around your mouth, a painful tongue, and fatigue. Over time, low amounts of vitamins and minerals can cause serious health problems. You may need to take vitamin and mineral supplements every day for the rest of your life to prevent this. The supplements include:

  • A chewable multivitamin with minerals (1 to 2 pills daily; take just before eating)

  • Calcium citrate with vitamin D (1,200 mg daily; take just before eating)

  • Other supplements, such as vitamin B12, as advised by your healthcare provider

When to call your healthcare provider

Call your healthcare provider if any of the following occur:

  • Pain, nausea, or vomiting after eating or drinking that doesn’t go away in 20 to 30 minutes 

  • Vomiting of blood or yellow-green fluid (bile) 

  • Diarrhea that doesn’t go away

  • Pain or discomfort in your upper back, chest, or left shoulder

  • Shortness of breath

  • Confusion, depression, or unusual fatigue

  • Urinating more than usual

  • Trouble urinating

  • Burning, pain, or bleeding when you pass urine

  • Hiccups that won’t go away

  • Night sweats

  • Fever

  • Chills

  • Anxiety, sadness, or other emotional problems

  • Trouble following advice about diet changes

Online Medical Reviewer: Jonas DeMuro MD
Online Medical Reviewer: Marianne Fraser MSN RN
Online Medical Reviewer: Raymond Kent Turley BSN MSN RN
Date Last Reviewed: 5/1/2022
© 2000-2024 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.