Gastric Bypass Diet


Gastric bypass is a type of surgery in which the stomach is reduced in size by one of several methods. This smaller stomach is then reconnected or bypassed to the small intestine. Having a gastric bypass can help speed weight loss by making it difficult to eat too much food at one time and to feel satisfied after very small meals.

After a gastric bypass, the volume the new, smaller stomach can hold is reduced from about 1 quart to about 1 ounce, or 2 tablespoons. Over time, the stomach pouch will stretch until it can hold 4 to 8 ounces, or about 1/2 to 1 cup, at a time. The size of the opening created between the stomach and small intestine is smaller, to roughly 1/4 inch wide, which slows the rate at which food is emptied from the stomach into the small intestine.

Gastric bypass is usually performed only after many other methods of weight loss have been tried and failed. However, the surgery is not an end in itself. It is important to work closely with a physician and registered dietitian (R.D.) to start a program of new eating habits to ensure that weight loss is safe and successful. A regular, simple exercise program and psychological support are often recommended to create a better self-image and a whole new attitude to food.

Vitamin and Mineral Supplements

Since the gastric bypass diet does not provide enough vitamins and minerals on its own, most physicians recommend taking:

  • 1 adult or 2 children's chewable multivitamin tablets
  • Extra iron, calcium, or vitamin B-12 if needed 

Nutrition Facts

The gastric bypass diet is designed to bring about significant weight loss. Learning new eating habits and following the diet correctly will help to maintain this weight loss over time. In general, the gastric bypass diet includes foods that are high in protein, and low in fat, fiber, calories, and sugar. Important vitamins and minerals are provided as supplements.

Protein is the nutrient that the body uses to build new tissue. It is important to get enough protein right after surgery, to make sure that wounds heal properly. Over the long term, protein in the diet will help preserve muscle tissue, so that weight can be lost as fat instead. Foods like lean red meat or pork, chicken or turkey without the skin, fish of almost any type, eggs, and cottage cheese are high in protein and low in fat.

Sugary foods include candy, cookies, ice cream, milkshakes or slushes, soda pop, sweetened juices or gelatin, and most desserts. The gastric bypass diet is low in sweet and sugary foods for three reasons. First, these foods are high in calories and fat. Even in small amounts, they could make weight loss difficult. Second, eating sweet or sugary foods promotes "dumping," a reaction which can occur after the gastric bypass operation. Experiencing the unpleasant symptoms of dumping syndrome may limit the desire to eat sweet foods. Finally, most sweet and sugary foods don't provide many vitamins or minerals for the calories they take up & and since calories are so limited on the gastric bypass diet, it is important that every food contribute its fair share of nutrients.

Fat may be difficult to digest after gastric bypass surgery. Too much fat delays emptying of the stomach and may cause reflux, a back-up of stomach acid and food into the esophagus that causes heartburn. Fat may also cause diarrhea, nausea, or stomach discomfort. High-fat, fried foods and fatty meats are common offenders.

Fiber, found in foods like bran, popcorn, raw vegetables, and dried beans, is also limited on the gastric bypass diet. There is less space in the stomach to hold these bulky foods, and less gastric acid available to digest them. Some kinds of fiber could get stuck in the pouch itself, or block the narrow opening into the small intestine. Do not take any fiber pills or laxatives without the advice of a physician.

Vitamins & Minerals are an important part of the gastric bypass diet. Since the diet allows only small amounts of a limited variety of foods, it may be difficult to get enough vitamins and minerals from food alone. Deficiencies can develop in a matter of months. Iron, folate, vitamin B-12, and calcium are the nutrients most affected. Most physicians require their gastric bypass patients to take a multivitamin/mineral supplement. 

Special Considerations

  1. Gastric bypass surgery creates dramatic changes in the size and shape of the stomach. It may take some time to get used to these changes. Patients report a wide variety of complications after surgery. Some of these will go away with time, while others can be lessened with adjustment of the diet.
  2. Nausea and vomiting are the most common complications occurring in the first few months after gastric bypass surgery. They may occur after eating too fast, drinking liquids while eating, not chewing enough, or eating more than the pouch can comfortably hold. It is necessary to learn to eat very slowly and chew foods thoroughly. Nausea and vomiting can also be triggered after trying new foods. If this happens, allow a few days to pass before trying a new food again. Notify a physician if frequent vomiting becomes a problem.
  3. Dehydration (loss of body fluids) is also an important concern, especially if vomiting or diarrhea is frequent. Prevent dehydration by drinking water or low-calorie beverages between meals (when there is no food in the stomach), but remember that the stomach can only hold 3-4 ounces at a time.
  4. Dumping Syndrome occurs when food passes too quickly from the stomach into the small intestine. Symptoms may include a combination of nausea, uncomfortable fullness, cramping, and diarrhea, or weakness, sweating, and fast heart rate. Dumping can be provoked by eating very sweet or sugary foods. Reduce intake of sweets and notify a physician if these symptoms occur.
  5. Food Intolerances, especially to red meat, milk, and high-fiber foods, are experienced by many patients. Since food intolerances vary with the individual, a dietitian can help with sorting out food choices to minimize symptoms such as stomach discomfort, nausea, or diarrhea.
  6. Overeating -- Almost all people who require gastric bypass surgery have had problems with overeating. The causes for this are complex, involving genetics, emotions, upbringing, and even the functions of the brain. None of this changes after bypass surgery, except that the stomach is now much smaller. Eating more than the new stomach can hold may cause vomiting, expansion of the pouch, weight gain, or even rupture of the stomach. Education, counseling, group support, and certain medications can help to prevent overeating and are just as important as diet to the success of the operation.
  7. Others: Stomach pain, ulcers, and gastritis (an inflammation of the stomach lining) are complications which may require medical attention. Notify a physician if frequent stomach pain becomes a problem.
Tips to Remember for Eating Right

In all stages of the gastric bypass diet, the way to eat is just as important as what to eat.

Things to remember:

  • The new stomach can only hold 1/2 cup at a time
  • Eat 3 to 6 small meals a day
  • Chew food thoroughly and eat slowly
  • Avoid chewing gum; could block the stomach outlet if swallowed
  • Do not overeat
  • Relax and enjoy your new life


Sample Menu
Breakfast Lunch Dinner
  • banana - 1/4 med
  • Scrambled egg - 1
  • toast, white -1/2 slice
  • margarine - 1 tsp 
  • broiled chicken breast- 2 oz
  • carrots, boiled - 1/4 cup
  • margarine - 1 tsp
  • pasta salad - 1/4 cup 
  • haddock, baked or broiled - 2 oz
  • green beans - 1/4 cup
  • dinner roll - 1/2 
Morning Snack Afternoon Snack Evening Snack
  • graham crackers - 2
  • pudding, sugar-free, made with 2% fat milk - 1/2 cup 
  • fruit cocktail, waterpacked - 1./2 cup 
  • cheese, American - 1 oz
  • saltine crackers - 2
  • mustard - 1 tsp 
*Consume nonfat milk between meals, throughout the day. Drink no more than 2 to 3 ounces at a time, for a daily total of 2 cups. 
This Sample Diet Provides the Following
Calories 1011 Fat 37 gm
Protein 71 gm Calcium 1065 mg
Carbohydrates 97 gm Iron 6 mg


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This material does not cover all information and is not intended as a substitute for professional care. Please consult with your physician on any matters regarding your health.

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