Why Do I Need A Liquid Diet Before Bariatric Surgery?

Once you have made the life changing decision to take control of your health and undergo bariatric surgery, it’s time to begin the preparation process. Completeness and detailed planning are needed to maximize your safety and achieve the success you are dreaming of. There are medical and surgical assessments, evaluations with nutritionists and counselors, as well as education on what to expect after your surgery and the steps you will need to follow in order to maximize your weight loss success. 

This can sometimes feel like a lot of information to digest, not to mention the fact that you are preparing your body to undergo surgery. While most bariatric procedures are performed using minimally invasive techniques requiring less down time, there are still measures every patient needs to take to ensure they are ready on the day of their surgery. 

One specific aspect is the pre-op liquid diet that bariatric patients must follow leading up to surgery. The following is a breakdown of the bariatric surgery liquid diet to help you understand exactly what it is and substances you should avoid before your bariatric procedure. 

What is the Liquid Diet Before Bariatric Surgery?

The liquid diet before bariatric surgery is a liquid-only diet prescribed to patients two weeks before their scheduled surgery date. This diet involves 4 to 5 vitamin-fortified protein shakes every day without any food or additional calories. This diet is essential to maximize your surgical safety and healing following surgery. It also helps kick start weight loss, helps ensure success of the bariatric procedure, and can help patients develop an idea of what their weight loss journey will be like post-surgery.

National best practice guidelines have identified this liquid diet as a clear way to reduce the operative risk associated with large fatty livers. Many patients suffering from obesity develop fatty livers, meaning their liver enlarges due to fatty infiltration as they’ve gained weight. Because the liver sits on top of the stomach,  a large fatty infiltrated liver can make it much more difficult to access the stomach and introduce unnecessary risk.

The liquid diet is proven to help reduce the size of fatty livers before surgery, producing a much safer operative environment. 

The liquid diet prescribed to you before your bariatric surgery includes several specific protein shake options that contain precise amounts of protein, vitamins, and reduced calories. Fatty liver also causes poor nutrition in your body which impairs wound healing after surgery. In addition, rapid weight loss can have an effect on healthy muscle mass, and consuming adequate protein per day before and after your surgery will prepare you for optimal wound healing and help you to ideally lose body fat rather than healthy muscle mass.

What Liquids Should I Avoid?

The most important groups of liquids to avoid during your pre-op liquid diet are carbonated and/or heavily caffeinated beverages like energy drinks. You should also stick to sugar-free beverages. Alcohol, which can also damage the liver and irritate the inner lining of the stomach, is also not permitted.

Below is a list of liquids that are best to consume during your 2-week pre-op liquid diet, although, again, each surgeon will have their own recommendations.

Recommended Pre-Op Liquids:

  • 4-5 protein shakes per day (several specific options)
  • Water (at least 64 oz per day)
  • Diluted vegetable juices (sugar-free)
  • Broth-based soups
  • Flavored Water (sugar-free)
  • Unsweetened Tea
  • Jell-O (sugar free)
  • Popsicles (sugar free)
  • Fiber supplements (to prevent constipation)

How Much Weight Can I Lose with A Pre-Op Diet?

The pre-op liquid diet is mostly implemented to prepare patients for surgery, not necessarily to help them lose weight. However, when strictly followed, patients can expect to kick start their weight loss and see some results even before surgery.

On average, patients can lose between 10-15 pounds on the liquid diet before surgery. This diet is designed to be low calorie and high protein, which will prepare your body for the weight loss following your procedure. While the weight loss achieved using a liquid diet is not indefinitely sustainable and is unlikely to yield long-term weight loss without surgery, your bariatric procedure is just around the corner to change your physiology and given you an optimal environment to lose maximum weight and sustain these results.

In addition, the more weight patients lose before surgery, the easier the surgery will be, which is another reason that it’s important to strictly follow the pre-op liquid diet prescribed by your surgeon.

Is the Pre-Op Diet Similar to the Post-Op Diet?

For the first two weeks following your bariatric procedure, your diet will look very similar to the liquid diet before surgery. During this time patients will need to stick to the all-liquid diet, similar to the pre-op diet for their safety as their stomach is healing. Two weeks after surgery, pureed or blended foods are reintroduced. Four weeks after surgery, you will be advance to foods with a soft texture. Finally, six weeks after surgery you will make it back to eating very well chewed regular, healthy foods. In the following months, bariatric patients must follow a new healthy eating plan that will have already been discussed as a part of the patient’s pre-op education. 

Proper hydration will also always be a top priority in every phase of both the pre and post-op diet. Patients need to be sure they are consuming enough water each day. Water can help prevent constipation, prevent nausea associated with dehydration, and actually may facilitate weight loss.

A Step in the Right Direction

Preparing for any kind of bariatric procedure involves a lot of information and personal preparation that can all feel very overwhelming. However, it’s important to keep in mind that rather this is a step in the right direction. 

As restrictive as the liquid diet before surgery is, remember that this is you taking back control of your health and your life. After their operations (whether it’s a gastric sleeve, gastric bypass, or duodenal switch) most patients lose between 100-200 pounds of unhealthy body weight or more. Imagine how that would feel! It’s time to start living the healthy energetic lifestyle you want, and the pre-op liquid diet before your surgery is the first step.

Dr. Joshua Long headshot

This page was medically reviewed by Dr. Joshua Long, MD, MBA, FACS, FASMBS. Dr. Long is a double-board-certified bariatric surgeon and bariatric medical director for Parker Adventist Hospital.
Full Bio: Dr. Joshua Long, MD, MBA, FACS, FASMBS
Page Updated: July 23rd, 2021

Lose Weight and Keep It Off With Bariatric Surgery

Are you ready to take the next step on your weight loss journey? Schedule an appointment with our friendly office staff today.

Schedule My Appointment

*Please note that individual results can vary and are not guaranteed.