Gastric Bypass Diet: What to Expect When Expecting (To Lose Weight)


A Gastric Bypass Diet is a doctor approved diet plan followed by those who have undergone Gastric Bypass Surgery, both after the surgery and in the weeks leading up to it. 

After Gastric Bypass Surgery, your body is going through an intense period of change and adaptability. Knowing what to eat - and in what quantity - is essential to the successful results of the operation. This means introducing serious changes in your food quality and intake. 

Your unhealthy eating habits and patterns have taken a lifetime to develop, and so ditching them for a healthier way of life will require immense strength and patience. Just remember, what won't happen overnight will definitely be worth the wait. 

The first step towards a successful gastric bypass diet is knowing what foods you can and cannot eat. This is important as the weeks following your gastric bypass operation are crucial to your health. Thus, a specialized diet designed specifically to tailor to your needs is just what you need:

  1. To give ample time to your stomach in order for it to heal from the operation and grow stronger without adding unneeded pressure.
  2. To allow your body to readapt to healthy eating options and get rid of its unhealthy ways in an effort to not only help you lose weight but to maintain the weight lost.


Prepping the body pre-operation plays a fundamental role in either the success or failure of the patient’s gastric bypass surgery. In order to reduce fat around the target zones in their body (liver, spleen, and stomach), the patient must consume a diet low in carbohydrates, fats, and sugars. Caffeinated and carbonated beverages must be avoided, and all liquids should be avoided thirty minutes before or after a meal. To prep successfully for this surgery, a patient should eat:

  • Protein Shakes/Meal Replacement Shakes

  • Broths (without chunks of vegetables or meats)

  • Soft Fruits and Vegetables in small quantities

  • Lean Meats (in small quantities)



The first week following Gastric Bypass Surgery is the most crucial and an all liquid diet is required for up to 7 days. The exact time period the patient will have to consume only liquids depends on their health and recuperating ability as determined by the patient’s dietician and medical health professional. This can include the consumption of:

  • Water
  • Fat-Free Broth (without any vegetable or meat chunks)
  • Low-Fat or Fat-Free Milk
  • Sugar-Free Gelatin
  • Sugar-Free Juice

These liquids must be sipped slowly in small quantities of 1-3oz at a time. Throughout the duration of this time, patients must avoid dehydration at all costs by drinking plenty of fluids.


After the initial one-week liquid consumption period, your body can now tolerate pureed sources of proteins. This stage of your post-op gastric bypass diet will last anywhere between 1 to 14 days, again depending on how fast your body is able to recover from the surgery. This can include pureed food sources such as:

  • Protein Shakes
  • Lean Ground Meats
  • Egg Whites
  • Beans
  • Fish
  • Non-Fat Cheese

This food should be blended with the use of liquids such as water, Fat-Free Milk, or Broth. Due to the decrease in the size of the patient’s stomach, the consumption of meals should be frequent and in small quantities. Water and other liquid intakes should be restricted 30 minutes before and up to 60 minutes after every meal.


After a successful period of the consumption of pureed foods, the patient can now move on to stage three of their post-op gastric bypass surgery diet. This will come approximately two weeks after stage two, and with the approval of their medical practitioner or certified dietician. Meals in this stage include:

  • Ground or Finely Diced Lean Meats such as Chicken or Turkey
  • Fish
  • Egg Whites
  • Non-Fat Cheese
  • Non-Fat Yogurts
  • Tofu
  • Cooked Vegetables (Peeled and Soft)
  • Soft Fruits (Bananas, Tomatoes, etc.)

Meals should be consumed frequently - about 4-6 times a day in small quantities of 1-2 ounces per serving. All foods should be cooked thoroughly or eaten when soft. This stage of the diet, like stage two, also focuses on high-quality lean protein and so that should be a staple in all your meals.


Stage four of the gastric bypass diet reintroduces solid foods into the plan for patients. This stage of the diet isn’t to be followed for a couple of weeks but is a permeant entity in the lives of gastric bypass patients.

Now that solid foods are back into their diets, they must be careful to watch what they eat, and what quantity they eat it in. Their stomachs are much smaller than ever before in their lives and so meals should be small, nutritious, and eaten frequently throughout the day.

This part of the diet needs to be introduced gradually after stage three and begun by introducing foods cut up into small pieces so as to aid digestion.

Certain foods should be avoided early on stage four as they are tough to digest and include:

  • Tough meats (such as Pork or Beef)
  • Nuts and Seeds
  • Shell Fish
  • Any form of Corn
  • Bread and other Whole Grains
  • Fried Foods
  • Carbonated or Caffeinated Beverages

The patient is still advised to eat in small quantities and frequently throughout the day. After about four months, or whatever time period the patient’s dietician recommends, the patient can then begin eating normally. Be advised that this means different things to different patients and caloric intake can be regulated from anywhere between 1000-1500 calories per day. Processed foods, excess carbohydrates and sugars should be avoided throughout the patient’s lifetime.


It is essential for patients who have undergone gastric bypass surgery to be regular with their intake of vitamins, minerals, and other supplements. Now that their stomach has decreased in size, and in turn their food intake has minimized, the use of vitamins and supplements will ensure the proper functioning of their body without any deficiencies. This includes the use of:

  • Multivitamins with Minerals
  • Calcium Citrate
  • Iron
  • Vitamin B12
  • Protein Supplements

These vitamins and minerals should be taken in chewable form as to reduce the amount of work your stomach would have to do in breaking down heavy pills.


Gastric Bypass Surgery is the beginning of a monumental change in lifestyle for those who go through it. Following the surgery and the maintenance of a healthy eating pattern, patients must incorporate a sufficient amount of physical activity and exercise into their routines.

This can be done in the form of either at home aerobics, taking long walks/going for runs, or visiting a gym and establishing a set exercise routine. Gastric bypass surgery isn’t the hard part; it’s keeping the weight that you lost through the surgery off where the most effort is required. Some easy to do exercises and physical forms of activity gastric bypass patients can partake in include:

  • Walking/Jogging/Running
  • Bicycling
  • Jumping Rope
  • At home aerobics such as sit-ups, jumping jacks, leg and arm spins
  • Lifting weights (to strengthen muscles)
  • Planking
  • Squats/Leg Press/Lunges
  • Core Training