If you have booked your weight loss surgery (whether it is a gastric bypass, sleeve, or band), it is time to start thinking about your bariatric pre surgical diet. This phase isn’t just about ticking a box or following another low fat plan, it is a medically prescribed, research-backed approach that plays a vital role in protecting your health during surgery. And we think that’s pretty important.

Over the years working in bariatric surgery, we’ve heard plenty of patient stories about falling into the trap of the "last supper syndrome" or assuming this phase is “no big deal.” We see it all the time on social media. But skipping over this step or treating it casually can make surgery more complicated, or in some cases, unsafe. Sometimes the type of surgery needs to be changed on the day, or worse, it can’t go ahead at all. Eek!

The good news? With the right preparation and support, this phase can be easier than you expect. And it’s not just a liquid diet - so keep reading!

Image courtesy of Your Complete Guide to Nutrition for Weight Loss Surgery.

WHY YOUR BARIATRIC PRE-SURGICAL DIET MATTERS

The bariatric pre-surgical diet, often called a Very Low-Calorie Diet (VLCD), is usually prescribed for 2 to 4 weeks before surgery. Its primary purpose is to shrink the liver and reduce fat around your stomach, which makes it easier and safer for your surgeon to perform the procedure.

A fatty liver has been compared to trying to lift jelly with chopsticks; it’s slippery, bulky, and hard to move. Shrinking the liver can help lead to a smoother, faster surgery and a better recovery for you.

HOW IT WORKS

The pre-op diet puts your body into a mild state of ketosis, where it starts burning stored fat for energy due to reduced carbohydrate intake. This helps:

• Shrink the liver

• Reduce abdominal fat

• Make surgery safer and faster. 

CAN YOU 'CHEAT' ON YOUR PRE-SURGICAL DIET?

Short answer: no. Even small deviations can pull your body out of ketosis and delay your progress. We know it is tough, but sticking to your plan is key. Follow the guidance from your bariatric clinic (or tap into our information) rather than relying on advice from well-meaning Facebook groups or forums.

Image courtesy of Your Complete Guide to Nutrition for Weight Loss Surgery.

TIPS TO STAY ON TRACK

✔️ Expect the first few days to be the hardest. Hunger, fatigue, nausea, and headaches are common. But once your body adjusts, your appetite often settles down.

✔️ Get organised. Stock up on your VLCD products. Our favourites include Optifast and Formulite.

This phase isn’t just about shakes, you can also include foods like diet jelly and low-carb veggies alongside your specially formulated protein shakes, bars, or soups.

✔️ Get creative. Flavour and texture can make a big difference.

• Stir-fry your veggies with garlic, ginger, or chilli.

• Make soups with allowed veggies, low-salt stock, herbs and spices.

• Oven-bake or air-fry mushrooms, cauliflower, or zucchini with a little oil and your favourite spices (we love the Mingle range).

• Steam greens and dress with lemon and cracked pepper.

For more recipe inspiration and ideas for both pre and post op (including your liquid and puree phases), check out our bestselling book, Your Complete Guide to Nutrition for Weight Loss Surgery.

✔️ Add variety. Flavour your shakes with sugar-free essences, syrups, or a shot of coffee. Try freezing shakes into frappes or serving with diet jelly, or using vanilla shake instead of milk in coffee (just limit caffeine to two drinks per day).

✔️ Stay hydrated. Mild ketosis can be dehydrating, so sip water and other allowed fluids like herbal tea or no-sugar water drops (such as Vital Zing). Limit carbonated beverages, even diet ones, as these are generally off-limits for at least three months post-op (or as advised by your clinic) so it is a great habit to break.

✔️ Keep busy. Take a walk, phone a friend, have a bath - anything to distract yourself when cravings hit.

✔️ Build a support network -Surround yourself with people who understand your goals and will keep you motivated.

NEED A LITTLE MORE HELP?

Preparing for surgery doesn’t have to be overwhelming. Our bariatric QuickStart Guide is just $7 and gives you everything you need to feel confident heading into surgery- and beyond.

Inside, you’ll find:

✔️ meal plans for your pre-surgical diet

✔️ recovery bariatric diet phase guidance (liquid, puree, soft)

✔️ what to avoid after surgery

✔️ when and how to start vitamins, fibre, and protein

✔️ FAQs from real bariatric patients.

Stop trying to piece it together from Google! This guide offers clear, structured support to set you up for success. Grab your copy here.