Understand the 
Gastric Sleeve Diet

Following the gastric sleeve diet is like training for a marathon. It takes time and patience and will look and feel different at various lengths from the start.

The pre op diet prepares your body for surgery and week 1-4 post op helps you heal and prevent complications.

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How Does Gastric Sleeve Surgery Work?

Vertical sleeve gastrectomy surgery (VSG) or “sleeve” for short…

…helps you lose weight by making your stomach smaller. Your stomach is reduced from about the size of a football to approximately the size of a banana.

cartoon football
cartoon banana

Yes, it’s true!  Before gastric sleeve surgery, your stomach can hold a volume of food about the size of large football!

Approximately 70-80% of your stomach gets permanently removed in surgery, leaving a narrow tube shape, that looks kinda like a shirt sleeve or a banana. ..

...Thus the name Gastric Sleeve Surgery. Personally I think Banana Surgery would have been better ;)

Why does the gastric sleeve diet work?

A: A smaller stomach hold less food. Which means you eat less calories. Which means you lose weight.

However...it's not a guarantee. You have to do your part.

"On Your Marks...Get Set:" 
The Gastric Sleeve Pre Op Diet

This is your “starting position” for the gastric sleeve diet "marathon".

1-2 weeks prior to gastric sleeve surgery, your surgeon will typically require you to follow a “liver shrinking diet.” Your liver is located above your stomach so it kinda blocks your surgeons view!  He/she must lift it during surgery to see your stomach.

If your liver is big and fatty, obviously the surgery is more difficult, and the risk of complications is greater.

The liver can shrink quickly by following a very low calorie, low carbohydrate, high protein diet. Thus, the gastric sleeve preop diet!

Make it Easy

To take all the guesswork out of it, many surgery practices, including the one I work with, use a simple bariatric specific meal replacement powder for the preop diet. It’s mixed with water and consumed multiple times per day. This assures the correct calories and bariatric macros without YOU having to calculate them yourself.  

Pre Op "Liver Shrinking" Diet (VLCD)

This is what “the liquid diet before surgery” means. By using the bariatric specific products, you’re assured of getting the high level of protein, vitamins, minerals, and fiber you need, while following a very low calorie diet ("VLCD"). This is very different than just drinking ANY liquids for 1-2 weeks pre op.

If you don't use the bariatric specific products, other surgery practices may suggest you drink 2-3 low carbohydrate, low sugar, protein drinks per day and eat 1 “Lean and Green” meal for your gastric sleeve preop diet. It could look something like this:

  • Breakfast: Protein Shake
  • Lunch: Protein Shake
  • Snack: Protein Shake
  • Dinner: Lean protein + Vegetables + 1 Tablespoon oil

Follow your surgeon’s instructions.

Post Op Diet

The following is a week-by-week description of what the post op diet typically consists of. Your surgeon's guidelines may vary slightly.

Important Note

In the first month post op, the gastric sleeve diet progression is to help you recover and to prevent complications triggered by improper foods. It’s extremely important to follow your surgeon’s post op diet instructions.

“Cheating" on your post-op gastric sleeve diet can cause side effects like:

  • Diarrhea
  • Dehydration
  • Constipation
  • Bowel obstruction
  • A very serious gastric leak

“And You’re Off!:”
Week 1: Clear Liquid Diet

cartoon runner

On week one of the gastric sleeve diet, you’re limited to fluids only. But don’t worry, you typically don’t feel hungry so it won’t be as hard as it sounds.

Your surgeon may instruct you to drink only clear liquids for the entire week or you may start out on clear liquids for 2-3 days and also be allowed full (thick) liquids for the remainder of the week. Follow your surgeon’s instructions.

You’ll only have 20-30% of your stomach left after gastric sleeve surgery…

…so drinking enough fluid will most likely be challenging. It won’t be like that forever, but it will take some strategizing in the beginning to get the required 64oz of daily fluids down.

There will be no gulping! Only sipping. Here’s a realistic pace to follow:

  • Drink 1 ounce every 15 minutes.
  • This equals 4 ounces per hour
  • This translates to 16 ounces every 4 hours

If you’re awake 16 hours (which means you get 8 hours of sleep), plan to finish four x 16 ounce water bottles every 4 hours. This totals 64 ounces!

  • 4 x 16 ounces = 64 ounces

Dehydration is the #1 cause of readmission post op. Set up an intentional fluid drinking schedule in order to plan for success. It may look something like this:

  • 6a-10a: 16oz
  • 10a-2p: 16oz
  • 2p-6p: 16oz
  • 6p-10p: 16oz

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 Week 2: Full Liquid / Pureed Diet 

In week 2 of the gastric sleeve diet, you can include all items from week 1 plus “full liquids” (thick liquids) and usually pureed foods if your surgeon allows it at this point.

Remember: The diet progression after surgery varies from surgeon to surgeon, so your exact progression might look slightly different. Be sure to follow your surgeon’s directions.

The purpose of the bariatric Stage 2 diet is to help ease your body into digesting “real food” and to begin working toward meeting a lofty protein goal (usually 60-80 grams protein per day)

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Week 3: Soft Foods

Week 3 of the gastric sleeve diet is when you finally get to introduce soft foods. There’s a little “trial and error” that goes on to determine what you best tolerate.

Don’t be surprised if:

  • Food “tastes different”
  • Everything tastes too sweet
  • Dairy is hard to digest

Some food intolerance is common in the beginning (causing gas, stomach upset, and/or diarrhea), but it doesn’t last forever.

Regarding Dairy

Some people develop a temporary lactose intolerance after sleeve surgery. If you feel gas and bloating caused by dairy foods, use a Lactaid pill, lactose free products like Lactaid milk or Fairlife milk, or switch to nondairy products like unsweetened almond milk, soy yogurt, etc.

If tolerate, nonfat/lowfat soft dairy foods like Greek yogurt, cottage cheese, and ricotta are good first choices (if you haven’t already included them in the pureed stage).

Scrambled eggs, beans, bean soups, vegetables soups, and well-cooked vegetables are good choices too. It’s smart to introduce foods slowly and only one new food at a time.

The goals at this stage are:

(Read more about the high protein bariatric diet)

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Week 4: Finally…Solid Regular Food!

At week 4, you can finally try regular, “real” food, assuming your surgeon’s diet progression allows it…

….but that doesn’t mean ANY solid regular food. This is not the time to start trying pizza!

It’s the time to put the healthy eating skills you (hopefully) practiced in the months leading up to surgery back into play.

Or it’s the time to put the pedal to the metal and start practicing healthy eating.  

Foods to try at this point may include:

  • Well cooked* chicken and fish
  • Cooked vegetables
  • Fruit
  • Nuts and seeds

*Well cooked” is important! You’re more likely to tolerate solid foods if they’re prepared using soft, moist cooking methods like crock pot, Instant pot, or poaching versus grilling or pan frying.

Foods that may still be hard to digest:

  • Steak
  • Raw vegetables


  • Bread
  • Pasta
  • Rice
  • Processed packaged snack foods
  • Sweets

Even though you’re 1 month out of surgery, your stomach is still sensitive, so go slow, take small bites, and chew each bite thoroughly. 

More about the Stage 4 Bariatric Diet and Menu Ideas

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Week 5 and Beyond

Beyond the first month, your gastric sleeve diet will continue to evolve. You’ll gradually be able to introduce a wider variety of foods as more time continues to pass. 

However, with a small stomach, it’s of utmost importance to choose nutrient dense food. Because you're eating less, every bite counts even more. 

The goal after surgery isn't to simply eat smaller portions of the same foods that got you into the predicament in the first place. The goal is to totally overhaul your diet and learn to eat healthier foods once and for all. 

Continue to introduce foods one by one to see how well they’re tolerated. .

Your long term diet should include:

  • Lean proteins
  • Vegetables
  • Fruits
  • Quality carbs 
  • Healthy fats

That’s not really any different than the “usual healthy diet” you always hear about! But having gastric sleeve surgery will likely make it more urgent for you to comply. Use the Stage 4 Food lists as a guide to your grocery shopping.

As with a race, it’s easy to quit when things get challenging or aren’t going the way you want them to go. Keep in mind, you’re not going to change an entire lifetime of habits in a month or two…

…or three or four.

Following a bariatric diet is a marathon, not a sprint.

A marathon is a test of mental toughness and willingness to press on when everyone else would most likely quit. And so it is with the gastric sleeve diet.

Gastric Sleeve Diet FAQs

Post Op Diet Progression:





Q: Will I Feel Hungry?

A: No. The hormone that causes you to feel hungry (called ghrelin) is made in the part of the stomach that gets removed.  

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