How to do a vegetarian diet for gastric bypass or sleeve

For health or religious reasons, bariatric patients might ask for a vegetarian diet for gastric bypass and sleeve or you might want to change your lifestyle and become a vegetarian after your bariatric surgery. A vegetarian diet plan after bypass or sleeve is possible. However, one should know anything and everything about their daily nutrient intake.

For those who are considering a plant based diet after gastric bypass or gastric sleeve, it is important to understand the different types of vegetarian diets. You should also know their benefits and drawbacks, as well as ways to ensure adequate nutrition and prevent deficiencies.

By the end of this article, you will know about the six types of vegetarian diets, learn what to include and exclude, and find ways to manage any nutritional deficiencies and minimize discomfort from gas. Additionally, you will learn about the pros and cons of a plant-based diet after bariatric surgery, and how to balance your portion size to ensure proper nutrition and avoid any drawbacks and risks.

6 types of plant-based diet

There are 6 subtypes of the vegetarian diet. These types are veganism, ovovegetarianism, lactovegetarianism, lactoovovegetarianism, pescetarianism, and flexitarianism. Each diet has its own restrictions, except for flexitarianism.

Veganism: Strictest form of vegetarian diet. Vegans restrict themselves from all animal products and by-products. They meet their protein needs with vegetables, legumes, tofu, and other foods that are rich in protein.

Ovovegetarianism: The restrictions are super close to veganism. Except, ovo-vegetarians do eat eggs and only eggs as animal products.

Lactovegetarianism: Lacto-vegetarians consume only dairy as animal products, such as milk, cheese, yogurt, etc. Other than that, their diet again consists of the restrictions of veganism.

Lactoovovegetarianism: Combination of lacto- and ovo-vegetarianism. Lacto-ovo-vegetarians include dairy and eggs in their diet.

Pescetarianism: Pescetarians eat only fish as animal products. However, many pescetarians pick and mix things. Some pescetarians also eat dairy, therefore are called lacto-pescetarians. Some include eggs, being called ovo-pescetarians. And some include both dairy and eggs in their diet. And they are called lacto-ovo-pescetarians.

Flexitarianism: Flexitarians rather avoid animal products as much as possible than restrict themselves from them. They occasionally consume animal products, especially minimally processed animal products. They also limit their sugar intake by all means.

You can cooperate with your dietitian to prepare a well-thought vegetarian diet for gastric bypass and sleeve. This way you can get all the necessary nutrients while following a specific diet without facing nutrient deficiencies.

What to eat and avoid in a vegetarian diet

Since a vegetarian diet mostly restricts animal product intake and indirectly prohibits the consumption of very rich protein sources like lean meats. That is why vegetarians should take close care of their protein intake.

What to eatWhat to avoid
  • Non-starchy, fiber-rich vegetables, and fruits
  • Imitation meat, soy ground beef, vegan meatballs, etc.
  • Protein-rich legumes
  • Tofu, tempeh, seitan etc.
  • Whole wheat bread
  • Sugar-free vanilla
  • Falafel
  • High-sodium imitation meat
  • Strachy and high GI fruits and veggies
  • Breaded falafel
  • Sweetened plant-based milk
  • White rice, pasta, white bread, etc.
  • Refined sugar
  • Fried foods
  • Processed food and snacks

You should absolutely avoid increasing carbs and fats in an attempt to compensate for lean meats. For instance, potatoes, carrots, and sweetcorns have a high glycemic index. Consuming these often and too much in one sitting can affect your blood sugar and cause weight gain.

You should opt for non-starchy vegetables and fruits that also have a low glycemic index. For example, you can have eggplant, asparagus, broccoli, cauliflower, chickpeas, etc. Also, there are vegan substitutes like soy ground beef, tofu, imitation meat, vegan meatballs, etc. that you can have to compensate for protein, provided they are low in sodium.

Pros and cons of a plant-based diet after surgery

You may find yourself wishing “I want a plant-based diet but I’ve had gastric bypass”. Well yes, a vegetarian diet for gastric bypass and sleeve is possible. But it does come with its own pros and cons according to various studies. Let’s review.

Pros are:

  • Reduces food cravings
  • Packed with healthy foods
  • Reduces chemical intake
  • Reduces the risk of heart attack, cancer, etc.

Generally, weight loss surgery diets will disclude processed food. With a vegetarian diet, it will be reduced even more. This will indirectly cause the risk of heart attack and cancer to be decreased.

Cons are:

  • Risk of nutrition deficiency
  • Possibility of weight gain
  • Less convenient
  • Not getting enough protein

To get enough protein, you may need to eat more substitutes, like chickpeas, than lean meats. And that can cause either nutritional deficiencies or it can cause the stomach to enlarge. And that can mean you may feel full later than anticipated. To avoid that, you should opt for richer protein sources such as tofu, lentils, quinoa, etc.

A vegetarian diet can be more challenging as it takes extra planning and extra tracking of your nutrient intake. However, it is all part of the journey. With the help of your healthcare provider, you can come up with a diet plan for you.

A study shows that omnivores and vegetarians can get a sufficient amount of nutrients in their diets if followed properly. Meaning a vegetarian diet can be as nutrient-dense as an omnivore diet and you can follow it without worry.

To benefit from the pros and avoid the cons, you should make early preparations for your diet. You can examine an exemplary shopping list below.

How to cope with nutritional deficiencies

If not tracked properly, it is easy to lack lots of healthy nutrients with vegetarian diets. To prevent that, one should be well-educated about the subject. The best way to avoid nutritional deficiencies is to contact your dietitian and prepare a well-thought-out vegetarian diet plan. This way, you will have a better understanding of what to eat and what to avoid along with how much of which protein sources you should take.

In a vegetarian diet, most protein comes from carbs and they can cause gas buildup. This can bring discomfort in your stomach and affect your eating. That is why planning a vegetarian diet plan thoroughly with your healthcare provider is essential before going through with the surgery. It is also hard to balance protein and carb intake appropriately while consuming carbs for protein, as too many carbs can affect glucose levels and hence the weight loss process negatively.

How to reduce gas pain

You should be really careful about what you eat. For instance, chickpeas are a great source of protein. However, they are known to cause gas buildup in the stomach and the intestines. This will indirectly cause gas pain as sometimes you might find it hard to release the gas. That is why you should avoid legumes and vegetables that can cause gas buildup during the first few months.

During your recovery, you will be recommended to walk and exercise regularly. This will also help with the gas pain by promoting bowel movements and proper circulation, so it helps release the built-up gas.

How to balance your plate

As a golden rule for diet after bariatric surgery, your diet should look like this: high in protein, low in fat, and moderate in carbs. To elaborate, your daily intake should consist of approximately 60-100 grams of protein, 26-42 grams of fat, and 50-100 grams of carbohydrates.

Sometimes, it is hard to determine how much food you should put on your plate. There are bariatric plates available you can find that show you how much of what to put on it. But for reference, your plate should look like this: 50% protein, 30% fruits and vegetables, and 20% carbs.


Protein intake is important

Protein intake is crucial after weight loss surgery. If you wish to follow a vegetarian diet, you should take extra care of your protein intake. A lot of rich-protein vegan foods are not recommended early on after the surgeries. So, you will need to find other sources, such as protein water and protein shakes.

During the first 10 days, you shouldn’t be consuming dairy products or plant-based beverages as they are not considered clear liquids. Instead, you can opt for protein waters. After you can consume dairy or plant milk, you can have a gastric sleeve or gastric bypass vegan protein shakes provided you prepare them with unsweetened non-dairy milk or vegetable broth.

As you move on to solid food, you will have more variety of options to get your protein from, such as legumes, tofu, chia seeds, falafel (not fried or breaded), imitation meats, etc. However, make sure the imitation meats you get are not high in sodium. Consult your healthcare provider before getting any imitation meats.

Reduce carb intake

During digestion, carbs turn into glucose in the body. This indirectly affects blood sugar. Most overweight/obese patients face insulin resistance problems. While insulin resistance is present in the body, it gets hard to lose weight because the body stores the excess sugar as fat. And if you already have type-2 diabetes, you should take close care of your carb intake.

Of course, your diet will be prepared specially for you minding your existing conditions. However, it is up to you to stand by them. If you do not reduce your carb intake, you may see a pause in your weight loss, or even experience weight gain.

A vegetarian diet plan for you

So, what can your vegetarian diet for gastric bypass and sleeve look like? You can find an exemplary daily meal plan below. This diet plan can be reshaped based on the type of your plant-based diet and your desires. You can also find lots of gastric sleeve and gastric bypass vegan recipes online.

P.S. This sample diet plan is for after 3 months post-op.


3tbsp of oats, 250ml soy milk, half a banana, and kiwi

Snack (optional)

Protein shake made with vegan protein powder and unsweetened almond milk


Pureed lentil soup made with vegetable broth and coconut cream


Hummus made with white beans and olive oil served with raw veggies like carrot sticks, cucumber, and bell pepper strips


Spinach and zucchini soup with tofu or tempeh


1 cup of unsweetened coconut milk

Esquivel MK. Nutrition Benefits and Considerations for Whole Foods Plant-Based Eating Patterns. American Journal of Lifestyle Medicine. Published online April 22, 2022:155982762210759.

Phan A, Hage M, Zaharia R, et al. Nutritional Status of Vegetarian Patients Before and After Bariatric Surgery: a Monocentric Retrospective Observational Case-Control Study. Obesity Surgery. 2023;33(5):1356-1365.

Giusti V, Theytaz F, Di Vetta V, Clarisse M, Suter M, Tappy L. Energy and macronutrient intake after gastric bypass for morbid obesity: a 3-y observational study focused on protein consumption. The American Journal of Clinical Nutrition. 2015;103(1):18-24.

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