Why Does My Breath Smell After Bariatric Surgery?

By: Laura Greaney, MSN

Congratulations, you have foul-smelling breath after bariatric surgery! Though this may seem like a trick, having rotten breath after bariatric surgery usually means you are losing excessive weight rapidly. This is a good thing. Many people often report their mouths feel dry or sticky right after surgery, regardless of what they do. This is caused by ketosis which is a metabolic process your body will undergo after surgery. Radically changing your diet post operatively is the main culprit for this side effect.

It’s no secret that you cannot survive without food. Food helps you to fuel your body so it can carry out necessary functions. Your body’s main fuel source is from glucose. Glucose can commonly be found in your starches, such as pasta and bread. Your body will break down these starches into simple sugars and either store them in your liver or use them to fuel your body. When you drastically reduce glucose, your body must find energy elsewhere. Ketosis is a condition where fat stores break down to give you energy since it can no longer rely on your high carbohydrate diet.

Rapid weight loss is the hope for most bariatric patients. However, it doesn’t come without a price. Every patient is put on a very restrictive diet for the first two months. The first few days after surgery the only thing patients are able to drink are clear, hydrating fluids. Due to this, the body is forced to burn off fat for energy instead of burning off carbohydrates. This process is called ketosis. Ketosis is a metabolic process where stored fat is broken down for energy resulting in higher levels of ketones. These higher levels of ketones include breath acetone which is responsible for that sweeter odor of the breath. This smell is increased in ketotic individuals. As stated in the American Journal of Clinical Nutrition, “Acetone is produced in the liver and is carried to the lungs directly via the portal blood. In the lungs, it equilibrates readily with alveolar air.” This is the cause for that smelly breath.

Many people will choose to have a month of bad breath when the flip side is a 30lbs weight loss. Unfortunately, if you experience this side effect, there isn’t much you can do but rest assure it will not last long. As Kenneth Burrell DDS Senior Director of the Council on Scientific Affairs of the American Dental Association stated, “All the brushing, flossing and scraping of the tongue that you can do is not possibly enough to overcome this change in diet.” However, there is hope. When you begin to start soft solid foods, roughly 5 weeks after surgery, there will be enough natural carbohydrates in vegetables that should resolve the stinky breath situation. It’s a small price to pay to begin a healthier life.


McIntosh, James. “Ketosis: What is Ketosis?.” Medical News Today. Retrieved from http://www.medicalnewstoday.com/articles/180858.php

Mann, Denies (Reviewed by Brunilda Nazario MD). “Low Carb Diets Can Cause Bad Breath.” WebMD feature
Musa-Veloso, K., Likhodii, S., and Cunnane, S. “Breath acetone is a reliable indicator of ketosis in adults consuming ketogenic meals.” American Journal of Clinical Nutrition 2002; 76:65-70.

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