Gastric Bypass Diet Plan

Fact Checked

imonkeybusinessimages/iStock/Getty Images

People who have undergone gastric bypass surgery have to make changes in how and what they eat, as well as how much they consume. Gastric bypass diets are created to deal with the specific nutritional needs of bypass patients. People can lose weight quickly after a gastric bypass, but face serious digestive and health complications if they don't strictly follow the diet.

Gastric Bypass Surgery

Gastric bypass surgery is the most frequently performed bariatric surgery in the United States, according to the Mayo Clinic. Patients undergo gastric bypass under general anesthesia, so they are unconscious during the procedure. During a Roux-en-Y gastric bypass, surgeons staple the stomach across the top, sealing it from the rest of the stomach, leaving a pouch big enough to hold roughly one ounce of food. The surgeon then removes the rest of the stomach and connects the small intestine to the newly re-sectioned pouch. Attaching the small intestine to the pouch allows food to bypass the stomach and the duodenum. Food enters directly into the jejunum, the second section of the small intestine, which limits the calories the body can absorb.


For the first one to two days following surgery, patients are on a liquid diet that includes broth, unsweetened juice, cream soups and gelatin; the patient sips only two to three ounces at a time. According to the National Institutes of Health, phase two of the diet lasts approximately two to four weeks after surgery; during this phase patients eat only pureed foods, including lean ground meats, beans, fish, egg whites, yogurt and fruits and vegetables. When the physician feels the patient is ready, she can move on to soft foods such as canned or soft fruits and cooked vegetables. This phase lasts approximately eight weeks. People gradually begin to eat firmer foods and build up a tolerance to spicy and crunchy foods.

Foods to Avoid

After gastric bypass, people should avoid certain foods that can irritate the stomach. Nuts and seeds, popcorn and dried fruits often cause gastrointestinal upset. People should avoid soda and carbonated beverages, as well, according to the Mayo Clinic. Stringy or high-fiber vegetables such as celery, broccoli, cabbage and corn can upset the stomach after gastric bypass, and should be avoided, as should breads, tough meats and granola.


People must keep meals small to avoid stretching the stomach and avoiding an upset stomach. Physicians recommend vitamin and mineral supplements following surgery to make up for the fact that bypassing part of the small intestine reduces absorption of nutrients. Patients should drink liquids between meals instead of with meals, as the combination can lead to nausea and vomiting, as well as causing people to feel full before ingesting the proper amount of nutrition. It's important to eat slowly and chew foods thoroughly, and introduce new foods one at a time to gauge how well the body responds, and to avoid foods high in fat and sugar and focus instead on high-protein meals.


Following gastric bypass people are at risk for nausea, vomiting and constipation. Another risk for gastric bypass patients is a disorder known as dumping syndrome; according to the Mayo Clinic, dumping syndrome occurs most often after eating high-fat or high-sugar foods. The foods move quickly through the stomach pouch and dump into the intestines, causing diarrhea, nausea, vomiting, dizziness, stomach cramps and flushing.