Following A Vegan Diet After Bariatric Surgery: Is It Possible?

May 23, 2022

Following a plant-based diet (e.g. vegan or vegetarian) is often discouraged by many health care professionals including surgeons and dietitians in the bariatric surgery space.

This leaves many patients feeling lost and confused as to whether they will need to add animal products back into their diet in order to have a safe and effective procedure. This can be quite distressing for those who have made the switch to plant-based for their ethical or environmental values.

The short version is that following a vegan or vegetarian diet after bariatric surgery is possible. However, there are a few caveats that you need to consider before jumping into the process.

The biggest challenge is meeting the higher protein needs with the recovery and weight loss process as well as managing the higher risk of nutrient deficiencies. Plant-based eaters also have much more limited choices in food/fluid options during both the pre-op and post-op diet stages.

Despite these risks, with some careful planning and the guidance of a plant-based dietitian experienced in the area, you can feel confident in your choice to pursue a plant-based diet throughout your bariatric surgery journey without putting yourself at risk of complications such as nutrient deficiencies or poor wound healing.


Nutrients at risk when following a vegan or plant-based diet after bariatric surgery

Plant-based or not, after undertaking bariatric surgery you are at a much higher risk of nutrient deficiencies. This is for two main reasons:

  1. Portion sizes are reduced post-surgery and lower food intake can mean lower nutrient intake
  2. During both gastric sleeve and bypass surgeries, your digestive tract is altered. This results in some nutrient malabsorption meaning that the body absorbs or uptakes less nutrients from food than it used to.

This risk is much greater during your first few weeks post-surgery when food/fluid intake is at its lowest. However, it is important to remember that these risks are life-long.

The most common nutrient deficiencies for all bariatric patients are protein, iron, B12, folic acid, vitamin D and thiamine. Other potential deficiencies include calcium, zinc and vitamins A, C, E and K to a lesser extent. However, for those following a vegetarian or vegan diet, the risk of these deficiencies (especially protein, iron, zinc, vitamins A and D and calcium) as well as iodine, selenium and omega 3 increases.

Because of this, you do need to take a bit more care when planning your meals and supplements to make sure you are getting everything you need (alongside the guidance of a dietitian of course).

We have listed below the top nutrients you need to be mindful of as a vegan or vegetarian after bariatric surgery and the best foods to add into your post-op diet. Most of these nutrients should also be contained in a good supplement routine to help fill in the gaps (more on this later).



Protein is arguably the most important nutrient post-bariatric surgery as it plays a key role in wound repair and recovery. It is also essential for helping maintain as much of your muscle mass as possible throughout your weight loss journey.

Requirements: Protein requirements after bariatric surgery are significantly increased to 1.1-1.5g/kg ideal body weight (IBW) per day. However, it is recommended that those following a plant-based diet have increased protein intake (roughly 10% more) to account for the fact that our plant-based proteins are poorer in quality than animal-based protein sources. Thus, we recommend aiming for 1.2-1.65g of protein per kg ideal body weight (IBW) per day.


To work out your ideal body weight (IBW) – this is your weight at a BMI of 25kg/m2:

Height in cm x height in cm x 25 = IBW in kg


For example, to work out protein requirements for someone who is 180cm tall:

  1. Find IBW: 1.8 x 1.8 x 25 = 81kg
  2. Find grams of protein per day range using 1.2-1.65g/kg/day:
    2 x 81 = 97g (lower limit)
    1.65 x 81 = 134g (lower limit)
  3. Requirements = 97-134g protein per day


Best vegan protein sources

  • 50g TVP = 27g
  • 1 cup cooked edamame = 25g
  • 150g firm tofu = 22g
  • 2 slices high protein bread = 21.5g
  • 100g pulse pasta (uncooked) = 21g
  • Protein powder = 20-30g
  • 100g tempeh = 15g
  • 1 cup beans and legumes = 10-15g
  • 1 cup quinoa = 13g
  • 2tbsp hemp seeds = 10g
  • 1 cup soy milk = 8g
  • 2tbsp nutritional yeast = 3.5g
  • 30g nuts or seeds = 2-5g


plant-based protein sources including nuts, seeds, legumes, beans, tofu



Important for normal red blood cell development, neurological functioning and supporting energy levels. After bariatric surgery, vitamin B12 absorption is decreased for all patients – both gastric sleeve and bypass making it one of the most common deficiencies. This is because the nature of the surgery decreases the stomach’s production of intrinsic factor which is necessary for uptake of B12 into our bloodstream.

Food sources: Unfortunately, there are no reliable vegan food sources of B12 (including fortified foods as absorption is limited) and additional supplementation is necessary.



Plays a crucial role in transporting oxygen around the body, supports energy levels and immune function. Those following a vegan or plant-based diet after bariatric surgery are at an increased risk of deficiency as the iron in plant-based foods is not as well absorbed by the body into our bloodstream.

Food sources: tofu, tempeh, edamame, beans and legumes, spinach, kale, hummus, fortified products e.g. Weetbix.

Pair with a source of vitamin C such as citrus, strawberries, kiwi fruit, capsicum, broccoli, potato or tomato to help optimise absorption.



Important roles in metabolism and immune function. Similarly to iron, the zinc in plant-based foods is harder for our bodies to absorb, increasing risk of deficiency.

Food sources: tofu, tempeh, soy milk, beans and legumes, pumpkin seeds, sundried tomato, oats.



Calcium is important for bone and teeth health – in particular preventing the development of osteoporosis, as well as muscle function.

Food sources: calcium-fortified milk (look for 120mg calcium per 100mL), calcium-set tofu, chia seeds, Asian greens, soy yoghurt, sesame seeds and tahini, almonds, and baked beans.



Aids absorption of calcium and helps maintain good bone health.

Food sources: there are no reliable plant-based food sources of vitamin D – some products such as plant-based milks may be fortified but this is unable to meet requirements.

Fortunately, our bodies are able to produce some vitamin D via sun exposure to our skin, however, there are many factors that can limit this.



Critical role in vision and eye health as well as immune function.

Food sources: There are no plant-based sources of vitamin A, however, our bodies are able to convert the beta-carotene found in many plant-based foods into vitamin A. These include orange fruit/veg such as carrot, sweet potato, pumpkin, rockmelon and papaya as well as dark green vegetables such as kale, spinach and broccoli.



Iodine is a necessary component of our thyroid hormones which support metabolism and energy levels.

Food sources: iodised salt, seaweed.



Supports a healthy immune system.

Food sources: 1-2 Brazil nuts per days can meet your needs.



Critical for heart and brain health.

Food sources: chia seeds, flax seeds, hemp seeds and walnuts.

An algae oil supplement containing the DHA form of omega 3 is also recommended as the body does not convert ALA (the omega 3 found in the above plant-based sources) into DHA very well.



In general, all plant-based diets including vegan and vegetarian diets are much higher in fibre than omnivorous diets. Whilst fibre is an important component of a healthy diet by helping keep us full and satisfied, aiding bowel movements and maintaining a healthy digestive system, after bariatric surgery, high fibre diets can sometimes be problematic by causing bloating and discomfort.

To add to this, many plant-based protein sources (such as beans and legumes) need to be eaten in greater volumes than animal-based products such as meat and seafood to provide the same amount of protein.

For example, to get 20g of protein from cooked chicken breast you only need to consume 70g. Whereas 20g of protein from chickpeas requires consuming 330g. As portion sizes have to be dramatically reduced post-surgery (¼-1 cup food volume per meal), getting in enough protein can be challenging.

Focusing on high protein lower fibre foods and fluids such as TVP, tofu, soy milk and mock meats and fortifying with protein powder when possible can make meeting protein requirements more achievable.


Navigating the bariatric surgery diet stages on a vegan/plant-based diet

Before and after you undergo bariatric surgery, there are a few specific diet stages that you must follow to ensure a safe and effective procedure and recovery.

This begins with a very low energy diet prior to surgery to help shrink the liver, and is followed by a set of different texture progressions following surgery: thin fluids, puree, soft and full.

Navigating these diet stages when following a vegan or plant-based diet after bariatric surgery can be challenging. Many of the resources you may be provided with by your doctor, surgeon or dietitian (or those you’ve found online), often don’t cater well to plant-based eaters. To help with this, we have put together a list of protein-rich plant-based foods and fluids for each diet stage.


PRE-SURGERY DIET (The Very Low Energy Diet)

The very low energy diet (VLED) requires the use of meal replacement products that are fortified with protein as well as all your essential vitamins and minerals. You have these instead of your usual meals and snacks. There are also a variety of other low-calorie fruits, vegetables, flavourings and fluids allowed. Typically, most of these products are not vegan-friendly as they contain ingredients such as milk powder or whey protein.

Unfortunately, vegan alternatives are limited in this space. However, The Lady Shake and The Man Shake now have a vegan option available which is a great alternative. As an added bonus, these products provide 30g of protein per serve which is higher than most generic meal replacement shakes.


brightly coloured fruit smoothies



Fluids at this stage should be thin with no lumps – think of the consistency of milk or a thin and strained soup/smoothie.

High protein options:

  • The Lady/Man Shake Vegan: 30g protein per serve
  • Vegan protein powder*: 20-30g per serve (will vary product to product)
  • Tonik Plant Protein shake: 20g per 330mL bottle
  • My Vegan clear vegan protein powder: 10g per 16g serve
  • Vitasoy Protein Plus almond/soy/oat milk: 10g per 250mL
  • Up & Go (dairy free): 8g
  • Low fat soy milk – 7g per 250mL

*When choosing a vegan protein powder, opt for a high quality protein such as a soy protein isolate or a pea and rice protein blend. Our 5 top picks are:

  1. Bulk Nutrients Earth Protein or Soy Protein Isolate
  2. MyProtein Soy Protein Isolate or Vegan Protein Blend
  3. Natures Way Soy Protein
  4. Botanika Blends Protein
  5. Coles Perform Protein (Vegan)

Low protein options:

  • Veggie juice
  • Electrolyte drinks e.g. Powerade zero, Gatorade no sugar, Hydralyte
  • Miso soup (broth only)
  • Thin soup e.g. pumpkin or tomato (blend through some tofu for an added protein boost)
  • Water

These can all be fortified with a tasteless protein powder such as:

  • Nature’s Way Soy Protein in Natural



Pureed foods should be smooth, lump free and slightly runny – think yoghurt or baby food consistency.

Meal ideas:

  • Pureed baked beans
  • Refried beans
  • Mashed tofu
  • Smoothie with protein powder + fruit + soy milk + optional veg (e.g. spinach, zucchini, cauliflower)
  • Pureed soups with vegetable and tofu/legumes (plus additional tasteless protein powder)
  • Pureed fruit or veg (plus additional tasteless protein powder)
  • Kingland soy yoghurt (plus optional additional protein powder)
  • Mashed soggy Weetbix with soy milk and protein powder
  • Sloppy quick oats with soy milk and protein powder
  • Muscle Nation Plant Protein Custard
  • Macro Mike Protein Pudding

TIP: Add nutritional yeast to savoury purees for an extra protein boost.



Foods should be soft enough to be easily cut through with the side of a fork. A sauce or other liquid should be added to any drier foods.

Additional meal ideas:

  • Soups or stews with vegetables and legumes
  • Tofu vegetable curry
  • Roasted or steamed veg with marinated tofu
  • Baked beans
  • Tofu scramble
  • Porridge or Weetbix with protein powder
  • Skinned cucumber sticks with hummus



This refers to a full texture diet, essentially incorporating all the different food textures you would have been eating before the surgery. However, the types and amounts of foods will most likely be different.

High protein breakfast ideas:

  • Scrambled tofu
  • Baked beans
  • Carmen’s protein porridge or standard oats with added protein powder
  • Soy yoghurt + added protein powder + fruit
  • Tofu or chickpea flour vegan frittata

Building a balanced bariatric meal:

  • ½ plate of protein-rich foods + ½ plate of non-starchy veg (all except for potato, sweet potato and corn)
  • ½ plate of protein-rich foods + ¼ plate of non-starchy veg + ¼ plate fibre rich whole grains and starches

Protein-rich meal ideas:

  • TVP mince with added veg
  • Tofu or tempeh stir fry
  • Mountain bread wrap with hummus, tofu/tempeh and salad veg
  • Burrito bowl with TVP mince + sauteed or salad veg
  • Dahl + veg

Protein-rich snack ideas:

  • Soy yoghurt + fruit
  • Apple or strawberries with powdered peanut butter
  • Roasted chickpeas or edamame
  • Steamed edamame
  • Hummus + vegetable sticks
  • Tin of marinated chickpeas

Tips for adding extra protein:

  • Top with nutritional yeast or hemp seeds
  • Opt for high protein grains if including such as quinoa, high protein bread or pulse pasta
  • Fortify meals with protein powder when possible
  • Add in some high protein fluids such as a protein shake, glass of soy milk or clear protein water


Georgia D'Andrea showing nutrition education booklet to patient


Post-surgery supplementation

Post-surgery, lifelong nutrient supplementation is necessary to avoid deficiency. This will usually include a bariatric specific multivitamin plus additional calcium, vitamin D, iron, B12, omega 3 or other nutrients as necessary. If you are following a vegan (or plant-based) diet after bariatric surgery, additional iron, B12 and omega 3 supplementation becomes especially essential.

Unfortunately, many supplements typically used post-bariatric surgery are not vegan. This may be due to the casing that the supplements come in or where the nutrients are derived from.

The main nutrients to look out for that are commonly derived from animal sources are vitamin D and omega 3. It is up to you to decide whether or not choosing a vegan supplement is important to you. If so, it can make choosing appropriate supplements a bit more challenging (but not impossible) with the guidance of a plant-based dietitian.

As supplementation will vary person to person based on individual needs, it is best to consult your dietitian to find out what supplementation routine will suit you best.

Schedule a free discovery call with our bariatric surgery dietitians at Plant Nutrition and Wellness.




This article was written by PNW Dietitian Georgia D’Andrea.

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