Proper nutrition before bariatric surgery (gastric sleeve, gastric bypass) directly affects the success of the surgery and the recovery process. In this comprehensive guide, you’ll find everything you need to know about preoperative nutrition rules, foods to avoid, and a sample liquid diet menu.

Why Is Preoperative Nutrition Important in Bariatric Surgery?

  • Reduces liver size – Makes the surgery technically easier
  • Lowers surgical risks – Decreases the likelihood of complications
  • Prepares the body for surgery – Balances metabolism
  • Initiates weight loss – Creates a pre-surgical advantage

Experts generally recommend starting a special nutrition program 2–4 weeks before surgery.

How Should I Eat Before Bariatric Surgery?

Protein-Focused Nutrition

  • Aim for 60–80 grams of protein per day
  • Consume lean meat, fish, eggs, dairy products
  • Consider bariatric protein powder supplements (with doctor’s approval)

Low-Carbohydrate Diet

  • Completely avoid simple sugars
  • Limit whole grain consumption
  • Keep daily carbohydrate intake below 50 grams

Healthy Fats

  • Include olive oil, avocado, and nuts (in moderation)
  • Avoid trans fats completely

Foods to Avoid Before Bariatric Surgery

  • Sugary foods (desserts, sodas)
  • Processed foods (sausages, salami, instant soups)
  • Fried and excessively fatty foods
  • Alcohol and caffeinated beverages
  • Raw vegetables (may cause bloating)

Preoperative Liquid Diet List (Sample Menu)

Usually, a liquid diet is started one week before surgery.

Morning

  • 1 glass of light milk or almond milk
  • 1 serving of bariatric protein shake

Snack

  • 1 bowl of fat-free yogurt
  • 1 tablespoon of flaxseed

Lunch

  • Vegetable puree soup (non-creamy)
  • 1 glass of buttermilk

Snack

  • 1 glass of freshly squeezed vegetable juice
  • A palm-sized portion of cottage cheese

Dinner

  • Chicken broth soup
  • 1 bowl of unsweetened compote

Preoperative Hydration for Bariatric Surgery: How Much Water Should Be Consumed?

  • Drink at least 2 liters of water per day.
  • Stop all fluid intake 12 hours before surgery.

Besides water, you can also consume:

  • Herbal teas (unsweetened)
  • Broths
  • Electrolyte drinks (under doctor’s recommendation)

Frequently Asked Questions

When should the preoperative diet start?

  • Typically, 2–4 weeks before surgery, but your doctor will set the exact timeline.

Can coffee be consumed during the liquid diet?

  • Caffeinated beverages are not recommended. Prefer herbal teas.

Should I take vitamin supplements before surgery?

  • Your doctor will create a specific vitamin supplementation plan if needed.

If you wish, you can check out our recipes at Bariatric Kitchen and visit our Türkçapar Bariatrics website for more information.