What Are the Bariatric Diet Stages?

by | Nov 22, 2023 | Nutrition and Hydration

If you’re thinking about weight loss surgery, one question you probably have, is around the post-surgery bariatric diet. There is a period of adjustment after surgery that requires a transition to solid food. This helps to support your recovery. The precise timing of that process can be different for everyone. So what’s right for one patient may not be the same for someone else. However, it can be reassuring to know what to expect in a general sense.

With that in mind, here’s a general overview of the different bariatric diet stages, and why these might be important for you to adhere to after weight loss surgery.

If you have had surgery, the best protocol is the one given by your surgeon or dietitian who actually knows you and your unique needs. If you’re in the early stages of thinking about surgery, I hope you find this general overview helpful as you start to gather information and make your important decision.

Are the bariatric diet stages different for every procedure?

In general, no. We don’t typically see much difference in the way patients tolerate the diet. We use the same 2/2/2 rule for all procedures. That is 2 weeks liquids, then 2 weeks puree, then 2 weeks soft, before transitioning to “normal” food. The bariatric diet stages may differ in timing depending on how you tolerate them. We make the 2 weeks liquid mandatory but there is some leeway with the puree and soft phases. Either way it will be six weeks before you start on normal food, albeit in very, very reduced quantities.

Why should I see a dietitian?

After weight loss surgery, you will be undergoing a complete change in the way you eat, and how you approach it. What doesn’t differ, is your need for optimal nutrition and hydration. A bariatric dietitian is best equipped to help you navigate nutrition and hydration to ensure you are meeting all of your needs. A dietitian will also be invaluable in providing tips and tricks to thrive on a weight loss surgery diet at every stage. We recommend a protein based diet, along with some healthy fats, and minimal carbohydrates. This is especially important for Roux-en-Y gastric bypass patients, where carbs can lead to dumping syndrome.

What are the dietary stages after bariatric surgery?

There are 4 phases to your post-surgery diet and there is also a pre-surgery protocol which you need to follow. This timing is very important for your health and safety and is evidence-based. For post-surgery care, we need to ensure that the normal swelling and oedema you would expect after surgery has subsided. Your stomach needs to be healed before reintroducing solid foods. You may feel well, but adhering to your surgeon’s recommendations will reduce the likelihood of complications.

Keep reading, or see the infographic below, for a summary of what’s involved at each stage.

bariatric diet stages

Preoperative diet

We may ask you to follow a very low-calorie diet (VLCD) for about 1-4 weeks before you are due to have surgery. This varies depending on your BMI. This is to help reduce the size of your liver and help make it more pliable by reducing the amount of fat in it (fatty liver/ hepatosteatosis/ steatohepatitis). This ensures a safer operation. Generally, your preoperative diet will consist of a protein shake/ soup meal replacement such as Formulite or similar liquid diet. We recommend Formulite as weight per volume it has up to 50% more protein and 50% less sugars than other replacement meal shakes and soups.

Protein keeps your hunger at bay for longer. The reduced sugar contents helps wean off sugary foods. It also has fibre and macrobiotics essential for gut health. Meal replacement shakes are NOT meant to be fun!! They are NOT the same as a milkshake. They should be palatable, sure, but primarily they are to provide adequate calories and micronutrients for the preoperative weight loss phase of your journey. Most people tolerate Formulite. If not you can talk with your dietitian about a suitable alternative.

1st stage post-surgery: liquids

Right after surgery, we need to go very slowly. You will need to sip, sip, sip. Liquids such as plain water, protein water, protein shakes (including those from VLCD phase), clear broths and soups, decaf tea or coffee, sugar-free jelly or flavoured water. The length of this stage is 14 days. You will find each day you can drink just that little bit more as the swelling settles. You need to get AT LEAST 1000 mL each day to avoid dehydration. Sip, sip, sip is the way. Usually around the second post op week you can start on your multivitamin, which you will take indefinitely. If you’re struggling to meet fluid and/or protein requirements contact your surgeon or dietitian.

2nd stage: purees

Stage 3 is the purees stage. and can be likened to the way we introduce food to babies. This is food pureed to a smooth consistency, with a view to providing a gentle introduction back to solid food. Your dietitian will provide recommendations here. Stage 3 is generally 1-2 weeks after stage 1 is completed.

3rd stage: soft foods

Stage 3 is about incorporating more solid (but still soft) foods and an overall protein-based, moderate healthy fats, low-carb diet. Your dietitian will guide you in eating small meals consisting of protein and vegetables at this stage. This diet will progress to stage 4 depending on your tolerance. generally 3-4 weeks after stage 2. It continues till around week 6 post-op.

4th stage: bariatric diet for life

Over time, you will find your tolerance for solid foods will grow, as will the amount you can eat at each meal. Your goals are to eat for optimal nutrition and of course, enjoyment. For most patients, you will feel full after very small meals. But you will still ENJOY them. The metabolic/ neurohumoral aspect of the surgery tricks your brain- you will feel full, satisfied and content after just a small amount of food. Interestingly your tastes may change. Every patient is different. Some say their tastes gravitate towards healthier options, and foods which are lower in sugar and fat.

As a weight loss surgery patient, you will need to monitor your diet and nutrient levels for life. But it will definitely get easier over time. I recommend seeing your dietitian regularly, especially in the first 12 months. This will help cement the important lifestyle changes you need for lasting weight loss, while the metabolic effects of surgery are in motion. You should also continue surgical follow-up to monitor weight loss, nutrition and overall wellbeing.

You should check in with your team (surgeon, bariatric G.P, dietitian, psychologist, exercise physio) whenever you feel that you’re steering off course. This happens to the best of us, and your team will quickly help get you back on track. This can be any time in the years after your surgery.

Disclaimer: This article is of a general nature for educational purposes only, and is not a substitute for medical advice. A 1:1 consultation with a medical professional is always the best approach in order to receive accurate information which is tailored to your individual situation. 

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About Dr Garth McLeod

Dr Garth McLeod is a Sunshine Coast General and Bariatric Surgeon. He is a Fellow of the Royal Australasian College of Surgeons (FRACS) in general surgery, with subspecialty training in obesity and metabolic surgery. Dr McLeod adopts a whole-patient approach to bariatric care with a multidisciplinary team