Gastric Bypass Surgery Post-Operative Diet

After patients undergo gastric bypass surgery, patients will be required to follow their surgeon’s post-operative diet to minimize potential nutritional side effects and complications. Following the post-op diet is crucial to a patient’s success.

The average gastric bypass patient will typically lose 5-15 pounds per week for the first 2 or 3 months, patients will then gradually taper down to 1-2 pounds per week after the first six months. If patients stop losing weight or reach a plateau, patients should re-focus on following the diet or starting at phase 1. Always consult your nutritionist before making any changes to your post-operative diet.

There are four important nutrition goals for gastric bypass surgery patients to keep in mind. When becoming acclimated to your new diet, make sure you are taking in enough protein as it helps reduce the loss of lean body mass and promotes healing in the body. Patients must also learn how to eat properly for their new stomach size.

Weight loss should always occur in a safe and healthy way through a healthy diet and regular meals at healthy portion sizes. It is also important to consume enough fluids in between meals to promote hydration, which also helps weight loss. Lastly, consuming the proper vitamins and minerals will reduce the risk of deficiency in the body.

Post-Op Vitamins, Nutrients, and Medication Requirements

Vitamins and Supplements: Patients are required to take multivitamins for the rest of their lives. Experts suggest taking 2 Multi-Vitamins each day, a B12 sublingual daily (under the tongue), iron, 400 IUs of Vitamin D daily and 2,000 mg Calcium Citrate daily. We do sell our own line of specialized Bariatric Surgery Post-Op Vitamins.

Acid-blocking medication: Patients need to take this medication for three months after surgery to lower the risk of stomach and bowel ulcers.

Medications to Avoid: Patients most avoid aspirin, ibuprofen, and any NSAIDs (non-steroidal anti-inflammatory). Patients will need to discuss every medication and supplement they take with their physician. Learn more about medications to avoid.

Stages of Post-Op Gastric Bypass Diet

  • Phase 1 – Clear Liquids Diet
  • Phase 2 – Thick Liquids Diet
  • Phase 3 – Soft Foods Diet
  • Phase 4 – Regular Foods Diet

Each phase lasts a total of 7 days.

Phase 1 Diet – Clear Liquids

Patients will need to consume roughly 4 ounces per waking hour. It’s also important to remember not to use straws as they increase the amount of gas and will make you feel uncomfortable. Patients will be in this phase for as long as their surgeon recommends (usually a week).

Approved Liquids:

  • Water
  • Clear Broth/Bouillon (chicken/beef/vegetable)
  • Sugar-Free  Jello/Popsicles
  • Sugar-Free Drinks
  • Decaffeinated Herbal Teas

Things to Avoid: 

  • Carbonated or Caffeinated drinks
  • Milk/Dairy/Protein Shakes
  • Alcohol

Your goal is to have at least 64 ounces of clear. sugar-fee liquids each day. Choose healthy drinks that will not cause you side effects, so avoid coffee or caffeinated drinks, or carbonated beverages. To avoid acid reflux, drink beverages in small sips and never more than 1 fluid ounce (medicine cup) at a time. Also, make sure you are waiting 60 seconds before drinking the next ounce. If the weather is hot or humid, increase your fluid intake to deter dehydration.

Learn More: Phase One: The Bariatric Surgery Clear Liquid Diet

Phase 2 Diet – Thick Liquids

This stage will include fuller liquids that are rich in calories.

Approved Liquids:

  • Blended Soups/Fat-Free Cream Soup
  • Fruit & Vegetable Puree (no seeds)
  • Protein Shakes
  • Sugar-Free Pudding
  • Cream of Wheat
  • Oatmeal
  • Sugar-Free Plain Yogurt (no fruit, no nuts)

During this phase, the patient will begin to transition from clear liquids to soft foods (phase 3). During this stage, you should focus on having enough protein while still taking in at least 64 ounces. Protein aids in proper wound healing after surgery so you want to aim for 60-90 grams a day.

It is important to have a protein supplement daily during this phase. Choose a low-carb option with less than 150 calories, at least 20-30 protein grams, and no more than 5 grams of sugar. Some good choices are 100% Whey Protein Isolate Bullets or Body Fortress® 100% Whey Protein Powder. If you are lactose intolerant, you may substitute rice or soy milk for cow’s milk.

NOTE: Thick liquids are considered a meal and do not count towards the 64 oz goal. You should follow the 30-minute drinking rule with your thick liquids.

Learn More: Phase Two: The Bariatric Surgery Thick Liquid Diet

Phase 3 Diet – Soft Foods

This stage will incorporate soft foods into your diet and will last a minimum of 7 days, depending on your nutritionist’s instructions. This phase will focus on eating at least 85 grams protein and consuming 550-700 calories per day. Aim for less than 40 grams of carbohydrates each day and less than 30 grams of fat.

Make sure to avoid any red meat, Turkey, Chicken, Veal, bananas, pureed melons, or overcooked vegetables.

Approved Foods:

  • Cottage cheese
  • Yogurt
  • Egg whites beaters or scrambled eggs
  • Tofu products
  • Ricotta cheese
  • Soft cheeses (low-fat options)
  • Hummus
  • Soft, flaky fish
  • Tuna (can have low-fat mayo)
  • Oatmeal
  • 1% Milk Pudding
  • Fruit, mashed (no seeds)

Eat several times a day and make sure you chew your food to an applesauce consistency. You want to introduce 1 new food per meal. The goal is to take small bites and wait 60 seconds before your next bite. Depending on your activity level, include a shake in your meal rotation. During this phase, aim for a high protein, low fat, low carb, and low sugar diet.

NOTE: Never drink while you are eating as it makes you full before you consume enough food. Never eat more than 4 ounces of food at one time.

Learn More: Phase Three: The Bariatric Surgery Soft Solid Diet

Phase 4 Diet – Regular Foods

Patients again need to focus on 100-120 grams of protein per day. This diet will be with patients for life, but again patients should aim for protein, whole grains, fruits, and vegetables.

At this point, your stomach should be ready for solid foods. You should have a good idea of how much food you can eat before you’re full and are well adjusted to your new eating patterns. Avoid eating anything with empty calories that provide you no nutritional value.

Long-Term Intake Goal: 

  • Each meal should have 3-4 ounces of protein
  • Vegetables 2 ounces
  • Fats: 1-2 Tbsp.
  • Carbs: 1 ounce

Learn More: Phase Four: The Bariatric Surgery Solid Food Diet

Things to Remember:

  • Avoid fast foods, junk food, or foods high in sugar or fat.
  • Avoid alcohol, soda, fruit juice, or anything high in calories.
  • Cut pieces of little meat – about the size of a penny cut in half. Chew each piece individually. This will promote natural digestion and a reduced risk of acid reflux symptoms.
  • Do not consume liquids with meals.
  • Eat slowly.
  • Stop eating when you’re full.

Ultimately, to maintain your weight loss, you must learn how to eat and what to eat to keep losing weight. Always eat slowly and think hard before consuming something. Think about what this contains and what will it do for my body. Weight loss surgery is the beginning of a new lifestyle to eat healthily and to live an active life.

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