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The Weight Loss Surgery Pre-Op Diet Demystified

Why Must You Follow the Pre-Op Diet?

The very strict diet that you follow for days or a couple weeks before surgery is intended to shrink the size of your liver and reduce the fat surrounding it to improve your surgeon’s vision in the area and access to the area during surgery.

Before that, your surgeon or health insurance company may require you to follow a less strict diet for a longer period of time. This can help you lose weight for a safer surgery and faster recovery. It also assures the surgeon and your health insurance company that you are serious, and that you will be capable of making the post-op dietary changes that you need for weight loss success.

Here is a little extra motivation to follow the pre-op diet, even if you are paying out-of-pocket for your surgery or your health insurance coverage does not require it. Any responsible surgeon will cancel your surgery if you do not follow it. This could be if you do not hit your weight loss goals and are not showing that you are capable of making the necessary dietary changes, or it could be while you are asleep and your surgeon has just gone in for surgery and discovered there is too much fat around your liver and spleen to perform surgery safely. Follow your pre-op diet!

Weight Loss Diet

Not every surgeon requires a longer term weight loss diet before starting your official pre-op diet, and you also may not need one if you are not planning to have your health insurance cover your surgery. This diet might last for 6 weeks to 6 months. It could be very structured, often with a low-carb theme, or it could be up to you to lose weight however you can.

Full Liquid Diet

A full liquid diet technically includes all liquids, but you should not have fruit juice or sugar-sweetened beverages since they just add calories without protein or many other essential nutrients. You can usually have:

Your surgeon may also allow you to have one meal a day consisting of a salad or vegetables and a serving of lean protein, such as chicken or tuna. A liquid diet is not fun, but it can be nutritionally adequate. You can follow it safely for days or weeks if your doctor tells you to do so. This is the diet you will be following for a few days to weeks post-op, too.

Clear Liquid Diet and Pre-Op Fast

A clear liquid diet includes only clear liquids; that is, you cannot have the protein shakes you had on a full liquid diet. Instead, you are stuck with water and other hydrating, low-calorie beverages, plus gelatin and sugar-free ice pops. Your surgeon may have you follow a clear liquid diet for only a day or two. It is not nutritionally adequate or safe unless your doctor is supervising you.

Final Fast

For at least 8 hours or overnight, according to what your surgeon says, you will fast before surgery. This is for safety reasons to prevent problems when you have anesthesia. Your pre-op instructions will likely forbid even plain water.

Differences Between Surgeons

Why do you see so many different pre-op diet plans? What if your surgeon says something different than what we say here? Follow your surgeon’s instructions! There is no single correct pre-op WLS diet. The one that is right for you is the one that you and your surgeon agree on based on your surgeon’s experience and your own situation.

For more information, check out the Pre-Op Diet Forums to see what others have posted and to post your own questions. With all the uncertainty surrounding your pre-op diet, one thing is sure: help is available on BariatricPal!

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