Plant Protein vs Animal Protein (Can You Get Enough Protein From Plants After Bariatric Surgery?)

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Have you been wondering if you can get enough protein by eating only plant proteins after bariatric surgery? Are you curious about what the difference is between animal protein vs plant protein? Is one better than the other after bariatric surgery? How does plant protein fit into your diet after bariatric surgery?

I am going to answer all of these questions in this blog post.

What is Protein?

Protein is one of three macronutrients in the food that we eat. The other two are carbohydrates and fat. 

Macronutrients are nutrients in our food that provide calories. Protein and carbohydrate both provide 4 calories per gram and fat provides 9 calories per gram. 

Protein is present all throughout your body and it is important for you to eat it every day. Proteins are made up of amino acids. There are 20 amino acids that your body needs to make these proteins. Some of these amino acids can be made by your body. Other amino acids can not be. These are called ‘essential amino acids.’ 

Essential Amino Acids

There are nine amino acids that are considered essential, which means that your body cannot make them and you need to eat an adequate amount of them. The essential amino acids are: 

  • Isoleucine
  • Methionine
  • Threonine
  • Valine
  • Leucine
  • Tryptophan
  • Phenylalanine 
  • Lysine 
  • Histidine 

What Happens If I Get Too Much Protein?

If you don’t have underlying health conditions it is unlikely that you would suffer health consequences from having too much protein. It is more important for you to choose protein foods that have other helpful nutrients like fiber and heart healthy fats rather than worry about whether or not you are eating too much protein. 

Sometimes after bariatric surgery people focus so much on eating protein that they forget about other foods that are important, such as fruits and vegetables or whole grains. 

Or they think that they need more protein no matter what. This sometimes leads to overeating as people sometimes seek out snacks between meals because they think they need to eat them, just to get more protein. 

This is not to say that you shouldn’t have snacks or that snacks can’t help you meet your protein needs. The point is that you should snack if you’re hungry and/or if you need to so that you can meet your nutritional needs. 

What Happens If I Don’t Get Enough Protein?

You are more likely to have trouble meeting your protein needs if your portions are still restricted after surgery than when you are further out from surgery and able to eat full portions. 

If you don’t get enough protein you could struggle with increased hunger, loss of muscle mass, fatigue, hair loss (although remember, this is also normal after surgery whether you eat enough protein or not), and fluid retention. 

Plant Protein vs Animal Protein: Advantages & Disadvantages

plant protein vs animal protein. kidney beans vs steak (photos)

What is Plant Protein?

Plant protein is in nearly all plant foods, but there are some plant foods that have a more concentrated amount of protein than others. Plant foods that have a more concentrated source of protein include:

  • Pulses: legumes, lentils, and peas
  • Soy: soy milk, tofu, edamame, tempeh, soy yogurt alternatives
  • Seitan
  • Nuts/Nut Butter
  • Seeds/Seed Butter

These protein foods vary in their protein content, with some having more than others. They also vary in the amount of carbohydrate and fat that they also contain in addition to the protein.

Advantages of Plant Protein vs Animal Protein

  • Plant proteins contain fiber. Fiber is helpful for keeping you full longer, for maintaining healthy cholesterol levels, and cancer prevention.
  • Contains heart healthy fats or are low in fat. Foods that are low in fat tend to be lower in calorie density, which can be helpful for weight loss. Eating foods that have predominantly heart healthy fats (monounsaturated and polyunsaturated) is helpful for heart disease prevention.

Disadvantages of Plant Protein vs Animal Protein

  • Many are less concentrated in protein than animal proteins.. This doesn’t usually cause a problem when you are further out from surgery but in the early days after surgery can sometimes make it more tricky to get enough protein.
  • Many do not contain all nine essential amino acids. You should eat a variety of different plant proteins to ensure you get all of the essential amino acids. 
Plant Proteins That Are a ‘Complete Protein’
  • Soy (soy milk, tofu, tempeh, edamame)
  • Quinoa
  • Chia Seeds
  • Nutritional Yeast
  • Amaranth
  • Hemp Seeds
  • Buckwheat
'complete protein' plant foods. soy: picture of edamame, quinoa: photo of quinoa, hemp seeds: photo of hemp seeds, nutritional yeast: photo of nutritional yeast, chia seeds: photo of chia seeds, buckwheat: photo of buckwheat, amaranth: photo of amaranth. vegan bariatric dietitian logo

What is Animal Protein?

Animal protein comes from animal flesh, eggs, or milk/milk byproducts. Animal protein foods vary in their protein content and in their fat content. They typically have very little carbohydrate content.

Advantages of Animal Protein vs Plant Protein

  • Animal proteins are for the most part quite concentrated in protein. This can be helpful in the early days after surgery when you can’t eat much.
  • Animal proteins typically (collagen is an exception to this) contain all nine essential amino acids. 

Disadvantages of Animal Protein vs Plant Protein

  • Many animal proteins are high in saturated fats. Eating too many saturated fats is a risk factor for heart disease.
  • Animal proteins do not contain fiber. Fiber is helpful for keeping you full longer, for maintaining healthy cholesterol levels, and cancer prevention.

How Much Protein Do I Need After Bariatric Surgery?

There isn’t enough evidence to direct the exact amount of protein you need to eat each day after bariatric surgery. The information that we do have recommends at least 60 g per day or 1.5 g protein per kilogram of idea body weight each day (for a person with an ideal body weight of 60 kg, this would be about 90 g protein per day). 

how much protein do you need each day? it is not known exactly how much protein you need each day after bariatric surgery. the available information that we do have recommends at least 60 g or 1.5 g of protein per kg of ideal body weight. for example: 1.5 g protein x ideal body weight in kg = grams of protein needed
Learn how to calculate ideal body weight (IBW) here

You can see that this is quite a range, further illustrating the fact that we don’t know exactly how much protein is enough after bariatric surgery. . This should be adequate for most people. 

So, if we don’t know how much protein you should eat each day after bariatric surgery, how do you know how much you should eat? There are some habits you can practice each day to make sure you eat enough protein. 

  • Eat at least 3 meals per day. Skipping meals decreases your opportunities to eat protein foods. You’re not going to get enough protein eating only one time per day. 
  • Include a protein food at each meal. 
  • Use protein shakes to meet minimum protein needs when your portions are too small to meet your protein needs. This is likely to occur when you are less than 3 months out from your surgery and may continue to occur for the first year after surgery. 
  • Include a snack with protein each day. 

How Do You Include Plant Protein in a Balanced Meal After Bariatric Surgery?

You can include plant protein in a balanced meal by filling half of your plate with the protein food(s) of your choice. On the other side of your plate include vegetables as ¼-⅓ of your plate and then fill the rest with fruit and/or starchy foods. You can also add a serving of healthy fat. 

plate with protein: black eyed peas, vegetable: broccoli & cauliflower, carb: whole grain bread, healthy fat: avocado

For a snack, you could have a protein food with a vegetable or a fruit or a starchy food or a healthy fat. 

balanced vegan bariatric snack: soy yogurt: protein & carbs + hemp seeds: protein & healthy fats + blueberries: fiber & carbs

To get all of the essential amino acids, you should include a variety of different plant protein foods in your day. For example, you should not only eat legumes for protein. You should instead have legumes as a part of your protein and have other foods, such as nuts and seeds or seitan as other parts. 

The only plant food that contains all of the essential amino acids is soy. The other plant proteins, such as legumes, nuts and seeds, and seitan do not contain all of the essential amino acids in the amounts needed by humans. This doesn’t mean that they are not good or that they are not healthy. It just means you should eat a variety of them each day to meet your protein needs.

What Plant Proteins Work Best for Each Diet Stage?

Full Liquids

During the full liquids diet stage after bariatric surgery your diet is very limited so it is important that the plant protein you are consuming contains all 9 essential amino acids. Choosing a protein shake made from soy will work for this. If you don’t tolerate soy or just want some variety look for a protein shake that has all 9 essential amino acids, such as OWYN.

See my article about the full liquid diet stage here.  


During the pureed diet stage after bariatric surgery your diet is beginning to expand but still quite limited. You should still be using protein shakes like on the full liquid diet but also able to have some other foods. 

Foods that work well on this stage are silken/soft tofu, hummus, refried beans, lentil soup, and soy yogurt alternatives. 

See my article about the pureed diet stage here.

Nut and Seed Butters

While nut and seed butters are technically a pureed texture I would recommend using caution with them at this stage after surgery. They can be sticky and sometimes people have trouble tolerating them. Sometimes it helps to include them in another food, such as cooked cereal or a smoothie.

person scooping nut butter out of a jar with a spoon


During the soft diet stage you will still likely enjoy protein foods from the pureed diet stage but you can expand to include more firm textures such as a medium firm tofu along with cooked legumes and lentils. Nut and seed butters are also more likely to be tolerated in this stage than in the pureed stage. 


The regular diet stage allows you to eat all of the protein foods from the prior stage plus the more textured protein foods, such as firm and extra firm tofu, seitan, tempeh, nuts, and seeds. You may find it more beneficial to include these more fibrous and more slow digesting foods as you get further out from surgery as they can be more filling. 

Protein shakes are great but sometimes a liquid isn’t very filling. 


Protein is an important part of a post-bariatric surgery diet and it is definitely possible to get enough each day with plant proteins. Knowing what foods are a good source of plant protein and then including them at each meal will make it very likely that you will get enough protein each day as a vegan after bariatric surgery.


“Inadequate Protein Intake after Bariatric Surgery: Effects on Body Composition and Sarcopenic Obesity.” Bariatric Times,

McGrane, Kelli. “13 Nearly Complete Protein Sources for Vegetarians and Vegans.” Healthline, Healthline Media, 21 Apr. 2020,

“Protein.” The Nutrition Source, 12 Nov. 2021,

Weight Management Dietetic Practice Group. Pocket Guide to Bariatric Surgery. Edited by Kellene A. Isom and Melissa C. Majumdar, 3rd ed., Academy of Nutrition and Dietetics, 2022.

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