Gastric Bypass Diet

Gastric bypass is a common surgery for weight loss in which the size of the stomach is reduced.1 Surgery can reduce the stomach size from one quart to one ounce.2 Due to such a drastic reduction in the stomach, gastric bypass can result in sudden weight loss, as patients often experience loss of appetite and feel full after a tiny portion of food.

Dietary management is critical in gastric bypass surgery. Not only is the stomach reduced in size, but the opening between the stomach and the intestine is also reduced (up to 75% of the original size). A reduction in the diameter of the opening slows the rate of movement of food from the stomach into the intestine. It is essential to keep a close eye on your diet after gastric bypass surgery to safeguard a more controlled weight loss process and to ensure that nutritional requirements are met.

Purpose of a Gastric Bypass Diet

  • Allows the stomach to heal properly after surgery
  • Trains the stomach to adjust to smaller and more frequent meals that improve the instant digestive process and the body’s ability to retain required nutrients
  • Helps prevent extreme weight loss in a short amount of time
  • Avoids possible complications associated with the surgery

The gastric bypass diet is designed to provide a slow and steady weight loss over time. Gastric bypass diets include protein-rich foods and are lower in fats, calories, fiber, and sugars.

It is important to know that the reduced caloric requirements of gastric bypass diets cannot meet the expected daily nutrient requirements for vitamins and minerals. In addition to the required gastric bypass diet, most physicians recommend:

  • A daily multi-vitamin tablet
  • Extra iron, calcium, or vitamin B-12 as needed3

Gastric Bypass Diet

The gastric bypass diet is a stepwise diet plan that begins as a liquid-only diet. It is slowly progressed to allow for introducing soft meals and then finally, small high-protein meals. Gastric bypass diet meals are smaller portions no matter which step you are on.

Clear Liquids

Immediately after bypass surgery, a clear liquid diet is recommended. The clear liquid diet will last 2–3 days after the surgery and includes water, sugar-free juice, diet gelatin, bouillon or clear broth, and flat diet soda like Diet Sprite.


Low-fat, Full-liquid Diets

When clinically appropriate, a clear liquid diet is then advanced to a low-fat full liquid diet. Patients are normally on this diet when they are discharged from the hospital, and it is continued for up to two weeks. A daily multivitamin is taken along with this diet.

Soft/Puree Diet

The full liquid diet is then advanced to a soft or puree diet. Soft foods may include scrambled eggs, low-fat cheese, cottage cheese, or blended lean meats like tuna fish, chicken, or pork. Soft food should be pureed and soft before eaten.

The high-protein diet is typically started around 8 weeks after surgery, and it includes all five food groups. It is best to include high-protein foods, like lean meats or milk, at every meal. Each meal must consist of small portions.

Specific Diets

Here are some recommendations for dietary guidance. These may be adjusted as necessary under the supervision of your physician.

It is crucial to prevent dehydration during every stage of the gastric bypass diet by drinking enough fluids.
  • Drink 1 cup of water or low-calorie beverage between each meal
  • Fluids should add up to at least 6 cups (48 ounces) each day
  • Sip slowly; make beverages last 30 minutes or more
  • Finish drinking liquids at least 45–60 minutes before meals
In all stages of the gastric bypass diet, the way to eat is just as important as what to eat. Things to remember:
  • Your new stomach can only hold 1/2 cup of food or beverage at a time
  • Eat 3 to 6 small meals a day
  • Chew food thoroughly and eat slowly
  • Avoid chewing gum; it 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, water-packed – 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 1,011 Fat 37 gm
Protein 71gm Calcium 1,065 mg
Carbohydrates 97 gm Iron 6 mg


  1. Seeras K, Philip K, Baldwin D, Prakash S. Laparoscopic Gastric Bypass. Fischer’s Mastery Surgery, Seventh Ed. 2021;1:1210-1217. doi:10.1016/j.suc.2020.12.013
  2. Wolfe BM, Kvach E, Eckel RH. Treatment of Obesity: Weight Loss and Bariatric Surgery. Circ Res. 2016;118(11):1844. doi:10.1161/CIRCRESAHA.116.307591
  3. Dagan SS, Goldenshluger A, Globus I, et al. Nutritional Recommendations for Adult Bariatric Surgery Patients: Clinical Practice. Adv Nutr. 2017;8(2):382. doi:10.3945/AN.116.014258

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