Pre Op Liquid Diet:
 4 Shakes + 1 Meal

Having weight loss surgery?  Here’s the lowdown on what you’re allowed on the pre op liquid diet:

There are no standardized guidelines for the pre bariatric surgery liquid diet, so there are many acceptable approaches. 

What to Have

The option I’ll describe here is a mostly liquid diet using approved bariatric specific meal replacement shakes + 1 whole food-based meal per day:

  • 4 bariatric specific meal replacement shakes
  • 1 whole food-based meal 

Like This:

  • Breakfast: Meal Replacement Shake
  • Snack: Meal Replacement Shake
  • Lunch: Meal Replacement Shake
  • Snack: Meal Replacement Shake
  • Dinner: Salad with 1 teaspoon added olive oil

In addition:

Drink 64 ounces of low calorie, sugar free, caffeine free beverages throughout the day.

Enjoy “free foods” as needed: sugar free jello, sugar free popsicles, and broth or miso.

Pre Bariatric Surgery Liquid Diet

Video Explanation

What to Have:
Pre Op Liquid Diet Meal Replacement Shakes

Meal replacement shakes are different from protein shakes.

A meal replacement shake provides a balance of macronutrients (protein, fat, and small amount of carbs)…and fiber too… just like a balanced meal would. Protein shakes provide just that…protein.

Don’t underestimate the distinction. It matters. The fiber and small amount of carbs in the meal replacement shakes makes all the difference in the world when you’re on the pre op liquid diet.

What to Have:
Pre Bariatric Surgery- Allowed Vegetables

Your daily whole food-based meal can consist of up to 2 cups of low carbohydrate (nonstarchy) vegetables and 1 teaspoon of oil.

Enjoy a variety of nonstarchy vegetables like these:

  • Arugula
  • Asparagus
  • Bok choy
  • Broccoli
  • Brussels sprouts


  • Cabbage
  • Cauliflower
  • Celery
  • Cucumber
  • Eggplant


  • Green beans/string beans
  • Hearts of palm
  • Jalapeños
  • Jicama
  • Mushrooms


  • Okra
  • Onions
  • Peppers-green, orange, red, yellow
  • Radishes
  • Sauerkraut
  • Snow peas


  • Sugar snap peas
  • Tomatoes
  • Yellow squash
  • Zucchini


Lettuce/Salad Greens: Arugula, Bibb lettuce, Butter lettuce, Collard greens, Endive, Green leaf lettuce, Kale, Mustard greens, Red leaf lettuce, Romaine, Spinach, Swiss chard, Watercress

What to Have:
Pre Op Diet- Food Based Meal Ideas

Garden Fresh Salad

1 cup salad greens (example: romaine, butter lettuce, spinach, arugula, and/or kale) + 4 added vegetables at ¼ cup each:

  • ¼ cup chopped tomatoes
  • ¼ cup sweet mini peppers
  • ¼ cup shredded carrots
  • ¼ cup sliced cucumbers

Top with 1 teaspoon olive oil, unlimited balsamic vinegar and spices as desired (pepper, dill, etc.)

Broccoli/Cabbage Slaw

  • 2 cups shredded cabbage or broccoli slaw
  • 1 tsp sliced almonds
  • Low sodium soy sauce or Lemon juice or Vinegar

Combine all ingredients and enjoy!

Stir Fry

4-6 different vegetables to total 2 cups. Example:

  • ½ cup sugar snap peas
  • ½ cup sweet mini peppers, sliced
  • ½ cup broccoli, chopped
  • ¼ cup diced onion
  • ¼ cup sliced mini portabella mushrooms

Sauté all vegetables in 1 teaspoon sesame oil. Season to taste with low sodium soy sauce, garlic powder and/or red pepper flakes.

Pre Op Diet:
What to Avoid

For the 2 weeks preop, avoid the starchier vegetables like these:

  • Beans/Lentils
  • Corn
  • Parsnips
  • Peas


  • Potatoes: white, sweet, and yams
  • Pumpkin
  • Turnips

Sample Meal Plan:
Pre Op Liquid Diet

  1. Drink your first meal replacement shake within the first hour of waking up, and then every 3 hours thereafter.
  2. Use the “free foods” in between as needed.
  3. End the day with your food-based meal.

A sample day could look like this:

  • 6am: Bariatric specific meal replacement shake
  • 9am: Bariatric specific meal replacement shake
  • 12pm: Bariatric specific meal replacement shake
  • 1:30pm: chicken broth if desired
  • 3pm: Bariatric specific meal replacement shake
  • 4:30pm: sugar free popsicle if desired
  • 6pm: Spinach salad: 1 cup spinach, ½ cup sliced cucumbers, ½ cup sliced tomatoes + 1 teaspoon of olive oil + balsamic vinegar as desired
  • 8pm: sugar free jello if desired

+ 64 ounces of calorie free beverages throughout the day

What to Expect:
Pre Op Liquid Diet Side Effects

Low Energy

You may feel tired or low energy because your calories and carbs are so low.

What to do: Drink at least 64 ounces of water or low-calorie sugar free beverages, get plenty of sleep, and avoid strenuous exercise during the 2 week pre op diet. Just take it easy!

Pre Op Liquid Diet Diarrhea

Unfortunately, yes, this is a potential :(

It's due to lactose intolerance or lactose sensitivity to the milk protein (whey protein) in most meal replacement shakes and protein drinks. Even if you have never been lactose intolerant before, this can happen due to the quantity of shakes you drink: 4 per day for a week = 28 liquid "meals." In two weeks that's 56 liquid meals. What comes in, goes out. You get the picture.

What to do: Talk to your surgery practice about switching to lactose free products or plant based products. Or START with them to begin with. This is the lactose free meal replacement drink I use with my patients:

Pre Op Liquid Diet:
The Takehome

  • There are no standardized guidelines for the bariatric liquid diet pre op, so there are varying approaches.
  • The preop diet doesn’t necessarily have to be ALL liquid.


  • The option I describe here is a way to approach the pre op diet that takes away some fear because you’re allowed some food. I love this approach because it takes all the guesswork out of what to eat, but still gives you a little “chewing” factor.
  • You may experience some expected side effects, but these are easily mitigated with the simple strategies I suggested. If you feel like you need 1:1 help to get through the pre op liquid diet, simply contact me! I will “hold your hand” through it!

Like This Info? Allow Me to Join You on Your Journey!
Credible, Professional Advice and Inspiration Delivered to Your Inbox:
Subscribe to Tiny Tummy Tips Newsletter

You might like these