The gastric bypass diet outlines what you can eat and how much after gastric bypass surgery. Find out ways to establish new eating habits for successful weight loss.

What you eat, how you eat and how much you eat changes after gastric bypass surgery — surgery that alters the anatomy of your digestive system to promote weight loss.

With your stomach pouch reduced to the size of a walnut or small egg and portions of your small intestine bypassed, you'll need to follow a specific diet after gastric bypass surgery. A registered dietitian can assist you in creating this gastric bypass diet, which includes what type and how much food to eat with each meal and the required consistency and texture of the food. Closely following your gastric bypass diet promotes healthier weight loss and better nutrition.

After surgery: The first three months

You won't be allowed to eat for one to two days after the surgery. Then you consume specific foods according to a diet progression. The purpose of the gastric bypass diet progression is to help in the healing process, minimize stress on surgical sites and allow time for your body to adapt to the new eating patterns.

The following are common phases in the gastric bypass diet progression:

• Liquids — foods and fluids that are liquid or semiliquid at room temperature and contain mostly water, such as broth, juice, milk, strained cream soup and cooked cereal. In most cases, you stay on a liquid diet for one to two days.
• Pureed foods — foods with a consistency of a smooth paste or a thick liquid. Pureed foods contain no distinct pieces. The pureed diet is generally followed for three to four weeks, or as recommended by your dietitian or doctor.
• Soft foods — foods that are tender and easy to chew, such as ground or finely diced meats, canned or soft, fresh fruit, and cooked vegetables. You usually eat soft foods for eight weeks before progressing to eating foods of regular consistency with firmer texture as recommended by your dietitian or doctor.

During the diet progression, you eat many small meals a day and sip liquids slowly throughout the day (not with meals). You might first start with six small meals a day, then progress to four meals and finally, when following a regular diet, decrease to three meals a day. Typically, each meal includes protein-rich foods, such as lean meat, low-fat dairy products (yogurt, cheese) or eggs. Protein is important for maintaining and repairing your body after surgery.

How quickly you move from one step to the next depends on how fast your body adjusts to the change in eating patterns and the texture and consistency of food. People usually start eating regular foods with a firmer texture three months after surgery, but it can occur sooner.

Lifelong changes: New eating habits

The changes in your digestive system restrict how much you can eat and drink with each meal. To avoid problems and to ensure you're getting nutrients you need, closely follow these guidelines:

• Eat small amounts. Just after surgery, your stomach holds only about 1 ounce of food. Though your stomach stretches over time to hold more food, by the end of three months, you may be able to eat 1 to 1 1/2 cups of food with each meal. Eating too much food not only adds more calories than you need but also may cause pain, nausea and vomiting. Make sure you eat only the recommended amounts and stop eating before you feel full.
• Eat and drink slowly. Eating or drinking too quickly may cause dumping syndrome — when foods and liquids enter your small intestine rapidly and in larger amounts than normal, causing nausea, vomiting, diarrhea, dizziness and sweating. To prevent dumping syndrome, choose foods and liquids low in fat and sugar, eat and drink slowly, and wait 30 minutes before or after each meal to drink liquids. Take at least 30 minutes to eat your meals and 30 to 60 minutes to drink 1 cup of liquid. Avoid foods high in fat and sugar, such as regular soda, candy and candy bars, and ice cream.
• Chew food thoroughly. The new opening that leads from your stomach into your intestine is very small, and larger pieces of food can block the opening. Blockages prevent food from leaving your stomach and could cause vomiting, nausea and abdominal pain. Take small bites of food and chew them to a pureed consistency before swallowing. If you can't chew the food thoroughly, don't swallow it.
• Drink liquids between meals. Drinking liquids with your meals can cause pain, nausea and vomiting as well as dumping syndrome. Also, drinking too much liquid at or around mealtime can leave you feeling overly full and prevent you from eating enough nutrient-rich foods. Expect to drink at least 6 to 8 cups (48 to 64 ounces) of fluids a day to prevent dehydration.
• Try new foods one at a time. After surgery, certain foods may cause nausea, pain, vomiting or may block the opening of the stomach. The ability to tolerate foods varies from person to person. Try one new food at a time and chew thoroughly before swallowing. If a food causes discomfort, don't eat it. As time passes, you may be able to eat this food. Foods and liquids that commonly cause discomfort include meat, bread, pasta, rice, raw vegetables, milk and carbonated beverages. Food textures not tolerated well include dry, sticky or stringy foods.
• Take recommended vitamin and mineral supplements. After surgery, your body has difficulty absorbing certain nutrients because most of your stomach and part of your small intestine are bypassed. To prevent a vitamin or mineral deficiency, take vitamin and mineral supplements regularly. These generally include a multivitamin-multimineral, calcium, iron, vitamin B-12 and vitamin D. Talk to your health care provider about recommended vitamin and mineral supplements following gastric bypass surgery.

Weight loss and weight gain

Within the first two years following surgery, you can expect to lose 50 percent to 60 percent of your excess weight, if you follow the dietary and exercise recommendations. If you continue to follow these recommendations, you can keep most of that weight off long term.

People who regain weight after gastric bypass surgery usually are consuming too many high-calorie foods and beverages and don't exercise enough. And rather than eating three meals a day and perhaps a planned healthy snack, some people engage in a grazing-type eating pattern — eating food all day long. Grazing often leads to consuming too many calories, which causes weight gain.

Successful weight management requires the following healthy habits:

• Limit or avoid high-sugar, high-fat foods, which provide many calories but few nutrients.
• Minimize unplanned snacking or frequent grazing, which increases calorie intake.
• Exercise regularly.
• Take the recommended vitamin and mineral supplements.
• Attend regular follow-up appointments with your health care provider to review your symptoms and progress and to make sure you don't have any vitamin or mineral deficiencies.

If you aren't losing weight or are regaining weight after surgery, see your doctor. He or she can help assess your eating behaviors and exercise habits and help you confront and overcome any weight-loss obstacles.

Though weight-loss surgery helps you shed the pounds, its success depends on your willingness to adopt lifelong healthy-eating and exercise habits. What you eat and how you eat changes after surgery, but the benefits of weight loss and your improved health are well worth these efforts.