Bariatric Weight-Loss Surgery

The Dangers of Being Underweight Following Weight Loss Surgery

Dr. Jason F. Moy
Dr. Brian T. Chin
Daniel Roman
The Dangers of Being Underweight Following Weight Loss Surgery

For patients undergoing bariatric (weight loss) surgery, being underweight may seem like a great problem to have. The purpose of these surgeries is to free the patient from all the health complications associated with obesity. To go from “obese” to “underweight”, for some, may seem like a best-case scenario.

But in truth, being underweight following weight loss surgery could be a serious problem. Malnutrition can present potentially life-threatening health complications, especially in those who have had weight loss surgery. This is why all patients must undergo a pre-op education program before undergoing weight loss surgery.

Doctors will usually prescribe specialized diets for patients to follow once their surgery is complete. These diets serve multiple purposes. First, they ensure that the patient can keep the weight off after having it removed. But second, the post-op diet ensures that the patient gets all the nutrients they need to continue living a healthy life. Not all “healthy diets” are beneficial for bariatric surgery patients. Many trendy diets should be avoided if you have had weight loss surgery.

Being underweight after weight loss surgery can have severe consequences. However, healthy eating and exercise habits, it is something that can be avoided. So how do you know if you are in danger of becoming underweight? And what can be done to avoid it?

Underweight BMI

You may already be familiar with the BMI (Body Mass Index) scale whether you have undergone bariatric surgery or not. BMI is a measurement of an individual’s weight relative to their height, generalized to the entire population. Patients undergoing weight loss surgery typically must have a BMI over 30 to be eligible for the procedures. A BMI of 30+ indicates obesity according to the BMI scale.

But BMI also measures whether or not a person is underweight. An underweight BMI is anywhere from 15 to 18. In any individual, an underweight BMI could be a sign of malnutrition, though this is not always the case. In a patient who has undergone weight loss surgery, an underweight BMI can be even more troubling. This is especially true for those who have undergone procedures like gastric bypass surgery. This procedure, and others like it, affect the body’s ability to absorb nutrients. This puts individuals at an even greater risk of malnutrition. Patients who have undergone these procedures often need to take vitamins and supplements throughout their life following surgery.

Am I Underweight?

If you notice yourself losing an unexpected amount of weight after bariatric surgery, it is natural to ask, “Am I underweight?” If you have concerns about being underweight, talk to your doctor as soon as possible. Those with a BMI underweight after weight loss surgery should not hesitate to seek medical care, because there are several dangers of being underweight. Symptoms from malnutrition may take years to set in, but the sooner you begin treating them, the better.

If you are underweight, your doctor can prescribe vitamins and supplements which will align with your existing post-op diet. This will not only provide you with essential nutrients but can also boost your energy.

Of course, it is important to remember that not all weight loss is bad. The idea of “bad weight loss” might not have even crossed your mind before. There are other identifiable signs of malnutrition to look for if you are uncertain about being underweight. These include:

  • Weakness and fatigue
  • Dry skin
  • Apathy or lethargy
  • Brittle hair

The most important thing you can remember before and after weight loss surgery is to listen to your medical team’s advice. If you would like to learn more about weight loss surgery options, contact BASS Bariatric Surgery Center. Our expert doctors can walk you through the processes of every available procedure, as well as pre- and post-op education.

About The Author

Daniel Roman, Content Writer

Daniel Roman is a Digital Content Writer at BASS Medical Group. He received his Masters in Journalism from UC Berkeley in 2021. Daniel has published multiple newspaper articles covering public health issues. His latest was a magazine cover story on pandemics and diseases that he co-wrote with Dr. Elena Conis, a historian of medicine, public health, and the environment.

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