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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 has a small opening at the bottom called a stoma. This can become blocked by food if you are not careful. In order 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.

  • Keep your weight loss goals in mind.

It is 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.

Your new stomach holds only a small amount of food now. You will need to measure your food before eating.

After Surgery

For 2 to 3 weeks after surgery, you will likely be on a liquid diet. You will then be able to eat pureed or soft foods only for an additional 2 to 3 weeks. Follow your health care provider's instructions for what liquids and soft foods are best. After this time, you can begin to bring other foods back into your diet.

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 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 general guidelines.

How Much to Eat

  • You should have 4 to 6 small meals per day.

  • Stick to 900 calories per day in the first 12 months.

  • Stick to 1,200 calories per day after that.

What to Choose

  • 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 Avoid

  • Avoid 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.

  • Avoid alcohol. It has calories, but not nutrients, and can slow your weight loss.

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:

  • Do not drink anything during a meal. You can drink again 30 to 45 minutes after a meal.

  • Take small bites. Chew your food 20 times before swallowing it. If you can’t chew something completely, do not 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. Eating too fast or too much can cause nausea and vomiting. It may also cause pain under your breastbone.

  • Do not snack between meals. This can limit your weight loss and even cause weight gain.

Preventing Complications

Certain problems can occur 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. Note down everything you consume, 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 or having dark yellow urine. The new stomach can only hold a small amount of liquid at one time. So it is 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. Do not use straws or drink out of bottles, as this may cause painful gas. Avoid carbonated drinks for the first few months, as they will also cause gas. Do not drink immediately before, during, or after meals. This can lead to food not being digested properly.

Get enough protein. Protein is a very important part of your new diet. It makes you feel full and keeps your body working normally. You will need to eat low-fat, high-protein foods with each meal. You should work your way up to 60 to 80 grams of protein per day. If you eat meat, make sure it is not tough or full of fat or gristle. If you can’t chew the meat thoroughly, don’t swallow it. It can block your stoma. Avoid 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

  • Lean cuts of beef and pork

  • 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 as 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 does not 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 one 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 lose the ability to digest lactose after surgery. If necessary, try lactose-free dairy products. You can also try taking 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 is related to the rapid entry or "dumping" of high-sugar meals into the intestine from the stomach pouch. It can happen 20 to 30 minutes after eating sugary foods. It can also happen after eating too quickly or too much at once. Symptoms include intestinal cramps, nausea, fast heart rate, and sweating. Diarrhea may happen 60 to 90 minutes after, but not always. 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 avoiding:

  • 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 maple syrup

  • 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 will 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 health care provider

When to Call the Doctor

Call your doctor if you notice any of the following:

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

  • Vomiting of blood or bile (green fluid) 

  • Diarrhea that doesn’t go away

  • Pain in your upper back, chest, left shoulder, or jaw line

  • Confusion, depression, or unusual fatigue

  • Urinating more than usual

  • Difficulty urinating

  • Burning, pain, or bleeding when you pass urine

  • Hiccups that won’t go away

  • Night sweats

Online Medical Reviewer: Grantham, Paula, RN, BSN
Online Medical Reviewer: MMI board-certified, academically affiliated clinician
Last Review Date: 2/28/2014
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