Gastric bypass is not for everyone. You must first qualify for the surgery and understand the risks and benefits involved. Those who are eligible are typically more than 100 pounds overweight or have a body mass index (BMI) over 40. You may also be eligible if your BMI is between 35 and 40 and your health is at risk due to your weight.

To be a viable candidate, you should also be ready to relearn your dietary habits. New dietary habits can help the surgery have positive and lifelong effects.

Before your surgery, you need to make plans for a special diet to follow before and after the surgery. The presurgery diet is geared towards reducing the amount of fat in and around your liver. This reduces the risk of complications during the surgery. After the surgery, your doctor with tailor the general diet guidelines to you. The diet consists of several weekly phases. It helps you recover, meet the needs of your now-smaller stomach, and gain healthier eating habits.

Losing weight before surgery helps reduce the amount of fat in and around your liver and abdomen. This may allow you to have a laparoscopy rather than open surgery. Laparoscopic surgery is less invasive. It requires much less recovery time and is easier on your body.

Losing weight prior to surgery not only keeps you safer during the procedure, but it also helps train you for a new way of eating. It is a lifelong change.

Your exact eating plan and preop weight loss goal will be determined by your doctor. Your eating plan may begin as soon as you are cleared for the procedure. If sufficient weight loss does not occur, the procedure may be cancelled or postponed. So, you should start the diet plan as soon as you can.


Guidelines vary from person to person, but may include the following:

  • Eliminate or decrease saturated fats, including whole milk products, fatty meat, and fried food.
  • Eliminate or decrease foods that are high in carbohydrates, such as sugary desserts, pasta, potatoes, bread, and bread products.
  • Eliminate high-sugar beverages, such as juice and sodas.
  • Exercise portion control.
  • Avoid binge eating.
  • Don’t smoke cigarettes.
  • Avoid alcoholic beverages and recreational drugs.
  • Don’t drink beverages with your meals.
  • Take a daily multivitamin.
  • Take protein supplements as protein shakes or powder.

What to eat

The pre-op diet consists largely of protein shakes and other high-protein, low-calorie foods that are easy to digest. Protein helps bolster and protect muscle tissue. This can help your body burn fat instead of muscle for fuel. Protein also helps keep your body strong, which can speed up recovery.

As the date for your surgery nears, you may need to follow a mostly-liquid or liquid-only diet. Based on your weight and overall health, your doctor may allow you to eat some solids during this time. These might include fish, watered-down hot cereal, or soft-boiled eggs.

Before the surgery, make sure you talk with the anesthesiologist for instructions about what you can or can’t have before the surgery. These suggestions are changing. They may want you to drink carbohydrate-rich fluids up to two hours before surgery.

After surgery, the diet plan goes through several stages. How long each stage lasts and what you can eat and drink will be determined by your doctor or dietitian. All stages stress the importance of portion control. This habit will help you continue to lose weight and prepare you for how you will eat for the rest of your life.

Stage one: Liquid diet

During stage one, your nutritional intake is geared towards helping your body heal from surgery. Your diet can help you avoid postoperative complications. For the first few days, you are only allowed to drink a few ounces of clear liquids at a time. This helps your stomach heal without being stretched out by food. After clear liquids, you will graduate to additional types of liquid. These include:

  • decaffeinated coffee and tea
  • skim milk
  • thin soup and broth
  • unsweetened juice
  • sugar-free gelatin
  • sugar-free popsicles

Stage two: Pureed diet

Once your doctor decides you’re ready, you can move on to stage two. This stage consists of pureed foods that have a thick, pudding-like consistency. Many foods can be pureed at home with a food processor, blender, or other device.

Spicy seasonings may irritate the stomach, so avoid these completely or try them one at a time. Avoid fruits that have lots of seeds, such as strawberries or kiwi. You should also stay away from foods that are too fibrous to liquefy, such as broccoli and cauliflower.

Instead, choose foods that liquefy well, such as:

canned fruits
Vegetablestomato juice
summer squash
green beans
white fish (cod, tilapia, haddock)
cottage cheese
ricotta cheese
scrambled eggs

V-8 juice and first-stage baby foods, which do not contain solids, are also convenient options.

As you start to include purees into your diet, it’s important not to drink fluids while you eat.

Stage three: Soft diet

You will probably eat nothing but pureed food for several weeks. Once your doctor decides you’re ready, you can start building soft, easy-to-chew foods into your diet. These may include:

  • soft-boiled eggs
  • ground meat
  • cooked white fish
  • canned fruits, such as peaches or pears

It is important to eat small bites. Use good portion control and eat a little at a time.

Stage four: Stabilization

Stage four of the gastric bypass diet includes the reintroduction of solid food. It typically begins about two months after surgery. You will still need to dice or chop your food into small bites because your stomach is much smaller. Large pieces of food may cause a blockage. A blockage can lead to pain, nausea, and vomiting.

Introduce foods slowly. That way, you can best determine which ones your stomach can tolerate and which ones to avoid. Eliminate any food that causes abdominal discomfort, vomiting, or nausea.

Foods to avoid in stage four

Certain foods should not be attempted yet, such as foods that are hard to digest. These include:

  • fibrous or stringy vegetables, such as pea pods
  • popcorn
  • corn on the cob
  • carbonated beverages, such as seltzer
  • tough meat
  • fried food
  • crunchy foods, such as pretzels, granola, seeds, and nuts
  • dried fruit
  • bread and bread products, such as muffins

About four months after surgery, you may be able to resume eating normally. However, portion control is still important. Make sure your diet consists mostly of fruits, vegetables, lean protein, and healthy carbohydrates. Avoid unhealthy foods that are high in fat, carbohydrates, and calories. Eating well means you can enjoy continued health without putting weight back on.

The guidelines for your postoperative diet will also serve you throughout life. They include:

  • Eat and drink slowly.
  • Exercise portion control.
  • Listen to your body. If you can’t tolerate a food, such as something spicy or fried, do not eat it.
  • Avoid high-fat and high-sugar foods.
  • Enjoy beverages between meals, but not during meals.
  • Drink enough daily to avoid dehydration.
  • Eat only small pieces of food at a time, and chew each piece thoroughly.
  • Take the vitamins your doctor recommends.

You may feel motivated to begin or resume an exercise program. Right after surgery, you need to let your body heal. Go slowly.

For the first month, low-impact exercises are a good option. These include walking and swimming. You may also benefit from simple yoga poses, stretching, and deep breathing exercises.

Over the next several months, you can build up slowly to strength training and cardio workouts.

Think in terms of movement as well as exercise. Simple lifestyle changes can be physical fitness boosters, such as:

  • walking instead of riding the bus
  • parking farther away from your destination
  • taking the stairs instead of the elevator

Following the proper pre- and post-surgery diets helps you avoid complications, such as dehydration, nausea, and constipation.


Sometimes the connection between your stomach and intestines can become narrowed. This can occur even if you are careful about what you eat. If you have nausea, vomiting, or stomach pain for more than two days, let your doctor know. These are all symptoms of an obstruction.

Dumping syndrome

Portion control and eating and drinking slowly also help you avoid what’s called dumping syndrome. Dumping syndrome occurs if foods or beverages enter your small intestine too quickly or in too-large amounts. Eating and drinking at the same time may also cause dumping syndrome. This is because it increases intake volume.

Dumping syndrome can happen at any stage of the postop diet. Symptoms include:

  • sweating
  • nausea
  • vomiting
  • dizziness
  • diarrhea

To help avoid dumping syndrome, a good rule of thumb is to take at least half an hour to eat each meal. Choose low-fat and low- or no-sugar foods. Wait around 30 to 45 minutes before drinking any liquids, and always sip liquids very slowly.

Gastric bypass surgery can give you a new start towards health and fitness. Following the preop and postop diet will go a long way towards your success. The right diet can protect you from surgical complications and teach you how to eat and drink well for the rest of your life.