We have decided to speak on this subject due to the current strong trend of society towards a diet free of animal products, mainly meat (vegetarian diet) and, in other cases, even eggs, milk and its derivatives (vegan diet). As surgeons, we are not experts in the subject, so we advise those who eat a diet of this type to have the advice of an expert in the field, such as a licensed nutritionist.


As a reader, if you are not a vegetarian you might think, how can a vegetarian suffer from being overweight or obese? The answer is simple; usually, people who adopt this type of diet do so at a specific time in their life but were previously omnivorous, and probably that change in the way they eat is done once they developed obesity, and / or some related diseases such as hypertension, high cholesterol, etc.


Article content:

The reality behind obesity in a vegetarian person
Pre-operative gastric sleeve diet for vegetarians / vegans
Observing the nutritional content of what you eat is the key
Gastric sleeve surgery IS viable if you are a vegetarian / vegan!




The reality behind obesity in a vegetarian person

obesity in a vegetarian person

The vegetarian diet by itself does not necessarily lead to continuous weight loss, it could only reduce weight gain, especially when it comes to people with a body mass index greater than 35 (discover your BMI), a situation we have explained in other articles, where the possibility of losing weight only with diet is significantly reduced, so they end up needing bariatric surgery to break that vicious circle. Discover if you are a candidate.


Another reason why a vegetarian could continue to suffer from obesity is even more straightforward, and this is, as in most cases of obesity, regardless of the type of food they eat: excessive food intake.


Next, we will give you our point of view and recommendations regarding the measures that a vegetarian or vegan patient should take in case that despite carrying this type of diet he/she is in a state of obesity that requires the support of bariatric surgery to achieve weight loss that leads to better health and quality of life.

First of all, it must be taken into account that eating this type of diet does not necessarily imply a loss of weight by itself since as you might know, the leading cause of obesity in our times is precisely the high intake of carbohydrates, refined sugars and processed foods.


Although a diet based on fruits, vegetables, seeds, nuts, and grains reduces or eliminates fat intake, the reality is that obesity is not consequence fat intake, but of eating all kinds of foods (mainly carbohydrates which are present in the vegan and vegetarian diet) and calories excessively.


It should also be noted that the fact of eating foods labeled as “free or low fat” usually implies that said food is “enriched” with other substances whose objective is to improve the taste and often these components are high in carbohydrates and sugars of some kind.


The most important thing to note is that when no meat is ingested, a vitamin B12 deficiency could develop, coupled with the fact that bariatric surgery alters the absorption of certain vitamins. Hence, it is essential to provide adequate vitamin and mineral supplementation, but more specifically, vitamin B12. It should be noted that after a gastric sleeve, any type of nutritional deficiency is much less likely compared to gastric bypass; in the case of the sleeve, when there are deficiencies, it is practically only Vitamin B12.




Pre-operative gastric sleeve diet for vegetarians / vegans

Certain general principles apply to every patient who is in preoperative preparation for weight loss surgery. Your bariatric surgeon likely has his/her own requirements for your preparation, but certain general aspects do not change regardless of whether the patient is vegetarian or vegan. It should be noted that usually (and in our case) the preoperative diet that we ask our patients does not even include solids. Still, this information is useful for the postoperative period.


Here are these general principles:


  • Seek to ingest high-quality protein from the various sources available (plants, legumes, milk and its derivatives, eggs, seeds, and nuts of all kinds)
  • Eat low in saturated fat food, trans fat, and cholesterol. Fat intake should not exceed 35% of the total calories ingested per day.
  • Avoid the intake of sugar and any of its varieties.
  • It is advisable to learn to read food labels (to the extent possible) the nutritional information that by law is found in almost all of the food and edible products available in the market. This will help you to have better control of what you eat as well as to discard those foods that are apparently adequate and are not.


A full article would be required to discuss the topic of food labeling, in general terms, look for foods low in carbohydrates and high in fiber, and don't forget to take into account the calories per serving! This is a detail that can make us think that it does not provide as many calories, and when we review the specified portion, we realize that they usually label much smaller portions than we typically eat!

  • Try to eat varied fruits to avoid getting tired of the same thing every day. We advise you to try fruits that you have never tried before.
  • Eat at least three meals a day, we recommend two “strong” and three small meals spread throughout the day.
  • Focus on eating fruits, vegetables, and whole grains, low in fat and especially low in carbohydrates.
  • Increase fluid intake (specifically water); the goal is 2 liters per day.
  • Increase your physical activity as much as possible; this will help not only to lose weight by burning calories but to improve your overall health as well as your lung capacity.
  • Finally, eliminate the intake of sugary drinks (soft drinks) from the diet, these usually have large amounts of refined sugars, in addition to being typically carbonated drinks (with gas), which in the operated patient it distends the “pouch” or new stomach that was created during surgery. This includes beer!


Getting into detail with the diet of a patient who is a vegetarian, the main focus should be the same, the intake of foods high in protein, low in fat and carbohydrates, we will present here several examples of the types of foods that vegetarian people usually eat and that are a good source of protein.



Observing the nutritional content of what you eat is the key

nutritional content of what you eat

It should be considered that in a diet without meat, the source of protein in vegetables and legumes per gram of food will be less than that achieved with beef. Because of this, as a vegetarian, you should pay extra attention to ingesting enough protein at each meal since because there will be less space available in your stomach to ingest enough protein if there is no meat intake. Eating eggs and dairy products could make the task much less complicated. Beans, tofu, soybeans (soybeans), and even vegetables such as broccoli contain protein, as you will see in our list below.


Vegetarian foods high in protein: (The percentage from carbohydrates and calories per 100 grams of the food is exposed as well as the percentage of calories that corresponds to proteins)*


table of nutritional content on a vegetarian or vegan diet


*Most of the nutritional value information in the previous list was obtained from the database of the United States Department of Agriculture. https://fdc.nal.usda.gov/


** NOTE: remember that in the list, in the protein column, it is not the grams of protein in 100 grams of the food, but the percentage of calories from the proteins in 100 grams of the food.

** We prefer to skip fats to avoid information overload, in addition to the fact that most foods are very low in fat.



Gastric sleeve surgery IS viable if you are a vegetarian / vegan!

As you can see, there are many options for appropriate protein sources if you eat a vegetarian diet. The best diet will always be the one that is varied and does not depend on a specific type of food. There are other sources such as quinoa, flaxseed, wheat, oats, sorghum, soy products, rice in its different varieties, etc.


Although the vegan and vegetarian diet are feasible after weight loss surgery (gastric sleeve, gastric bypass, or other bariatric procedures), it is definitely not a simple task because of the available stomach space to ingest enough protein. Taking this type of diet requires effort and planning since it cannot be the “typical” animal protein and accompanying vegetables.

In addition to that, several vegetarian options usually expand in the new stomach and cause the patient to feel very full or too fast as with pasta, rice, and some vegetables such as lettuce.

Besides, patients in preparation for surgery, usually require a preoperative diet, which in our case we ask for a liquid diet in which one of the primary sources of protein is whey protein, and as vegan you will not want to take this supplement, making the situation more complicated.


Outside of these details, a vegan or vegetarian patient can undergo the gastric sleeve without a problem and without risk of developing any deficiency as long as it is in an orderly and systematic way. In this particular case, due to the type of diet, vitamin supplementation for life would be advisable, unlike omnivorous patients with gastric sleeve who usually only require supplementation for some time until they make the necessary adjustments in their lifestyle and eating habits.


Know if you are a gastric sleeve candidate.