Everything You Need to Know About Bariatric Surgery + Gut Microbiome Changes

Everything You Need to Know About Bariatric Surgery + Gut Microbiome Changes

Millions of Americans struggle with obesity. Despite hard work, diet, and exercise, many of those suffering from the condition can’t seem to get to a healthy weight. So, after trying all other known options, some opt to undergo bariatric surgery. 

And, despite what some people believe, a surgical approach to weight loss is not a quick fix. Bariatric surgery comes with a unique set of advantages and disadvantages. Here, learn what you need to understand about your surgical weight loss options before you talk with a surgeon. Then, learn the effects of bariatric surgery on your gut microbiome. 

What is Bariatric Surgery? 

Bariatric surgery is the name given to gastric bypass and other weight-loss surgeries. A gastric bypass surgeon makes changes to the digestive system to help patients lose weight and prevent the onset or reduce symptoms of existing obesity-related and life-threatening diseases.  

Currently, there are currently less than a handful of bariatric surgery procedures.  

  1. Gastric bypass
  2. Sleeve gastrectomy
  3. Adjustable gastric band (lap band)
  4. Biliopancreatic diversion with duodenal switch

Bioscience of Microbiota

[Image source: Bioscience of Microbiota, Food and Health Vol. 38]

Each type of surgery comes with its own pros and cons, which should be discussed thoroughly with a doctor. 

Who is a Good Candidate for Bariatric Surgery? 

According to the American Society for Metabolic and Bariatric Surgery, a patient must meet one of three criteria for bariatric surgery requirements. 

  1. A BMI above 40 (class 3 obesity) or 100 pounds over a healthy weight. 
  2. A BMI above 35 (class 2 obesity) and at least one obesity-related core morbidity.
  3. An inability to achieve a healthy sustained weight despite serious efforts. 

The core morbidities that qualify class 2 obesity patients for bariatric surgery are

  • Type 2 diabetes
  • Hypertension
  • Sleep apnea & other respiratory disorders
  • Non-alcoholic fatty liver disease
  • Osteoarthritis
  • Lipid abnormalities
  • Gastrointestinal disorders
  • Heart disease

For more information, see: This is the Truth About Obesity (It's Not What You Think)

Comparison of Bariatric Surgery Procedures

Which surgical weight loss procedure is the best? Look closely at the details for each type of bariatric surgery so you know what to expect. 

Average Cost, Procedure Time, Recovery Time, and Excess Weight Loss Percentage by Bariatric Surgery Procedure Type

Learn the average costs, insurance coverage, procedure time, recovery time, and excess weight loss time for gastric bypass, sleeve gastrectomy, adjustable gastric band, and biliopancreatic diversion with duodenal switch. 


Procedure Time

Recovery Time

Excess Weight Loss

30-Day Mortality Rate

Serious Complication Rate

Gastric Bypass


2-3 hours

3-5 weeks




Sleeve Gastrectomy


1-2 hours

3-5 weeks




Gastric Band


1-2 hours

3-5 weeks




Duodenal Switch



6-10 weeks 




*According to numerous sources, average excess weight loss varies in subgroups of patients in different BMI categories prior to surgery for all weight loss procedure types.  


The weight loss surgery with the lowest risk of death and serious complications is the sleeve gastrectomy. The mortality rate for up to 30 days after the procedure is 0.08%. And, only 0.96% of sleeve gastrectomy patients end up with serious problems resulting from the surgery. 

Does Insurance Cover Weight Loss Surgery? 

With the high costs, patients ask if their health insurance will cover a procedure. In many cases, bariatric surgery can be covered by insurance with preapproval. Coverage varies for patients and providers. For example, Medicare covers gastric bypass and laparoscopic gastric banding when patients meet certain criteria. And, BlueCross BlueShield includes weight loss surgeries at designated facilities in its healthcare plans. 

How Fast Do You Lose Weight After Bariatric Surgery? 

Patients begin to lose weight just days after bariatric surgery. Those who undergo a surgical weight loss procedure must follow a strict, high-protein, low-sugar, low-fat diet.  Doctors expect weight loss goals to be achieved within about 12 to 18 months after the procedure. At this point, weight loss might plateau. After this, many patients start to put some of the weight back on. 

What are the Effects of Bariatric Surgery on a Patient’s Gut Microbiome?

Following bariatric surgery, notable changes take place within the gut microbiome. There are four major reasons noted for this phenomenon. 

  1. Decreased food intake
  2. Nutrient malabsorption
  3. Altered food preferences
  4. Increased stomach pH 

In short, the dietary changes following the surgery play a role in changes to the patient’s gut microbiota composition. 

And, when the volume of the stomach decreases, the pH increases, which affects all aspects of digestion. Within the digestive system, Bacteroidetes decrease and Firmicutes and Actinobacteria increase due to the pH increase following weight loss surgery. 

In addition to the decreased volume of the stomach, changes to the gut microbiome play a key role in the effectiveness of bariatric surgery. 

How Dangerous is Bariatric Surgery? 

Is weight loss surgery safe? The average mortality rate for bariatric surgery is 0.93% or less. As with all major and invasive procedures, bariatric surgery has a list of common and rare side effects

  • Acid reflux
  • Addiction transfer
  • Anesthesia-related risks
  • Bowel obstruction
  • Chronic nausea and vomiting
  • Dilation of esophagus
  • Dumping syndrome
  • Hernias
  • Inability to eat certain foods
  • Infection
  • Low blood sugar
  • Malnutrition
  • Obstruction of stomach
  • Suicide
  • Ulcers
  • Vomiting

Furthermore, each procedure comes with its own set of risks, unique to other types of weight-loss surgeries.  

Are There any Effective Bariatric Surgery Alternatives?

While bariatric surgery is a powerful weight-loss method, the dangers, cost, stigma, and other factors keep many people from electing a surgical procedure. In fact, only a small percentage of patients who are eligible candidates ever take the steps to follow through with this type of surgery. So, are there any safe and effective alternatives?

With the rate at which technology and science advances, it is no surprise that other methods for losing weight are disrupting medicine. So, what are they? 

First, the intragastric balloon is a non-surgical procedure that was approved by the FDA in 2015. A saline-filled balloon is placed into the stomach of the patient to inhibit hunger. The procedure is also fairly costly and comes with several risks and side effects. 

Now, circle back to the advances in science and realize that many medical breakthroughs focus on the truth about obesity. The fact is genetics and gut microbiome are central contributors to weight gain and that every human body is unique. So, for a complete picture of your health and contributors to a high BMI, weight loss patients should inquire about DNA and gut microbiome sampling. 

Does Insurance Cover Gut Microbiome and DNA based Weight Loss Programs ? 

Insurance companies like Blue Shield of California cover Gut microbiome and  DNA based personalized weight loss and obesity programs that target weight loss , while reducing risk or reversing obesity associated inflammatory skin disease, hypertension, gut disorders , diabetes, PCOS . 

Final Thoughts

Bariatric surgery is an effective weight-loss method, but each procedure comes with risks. Death from surgical complications, while rare, is a very real possibility. Is a surgical weight loss plan right for you? 

Digbi Health has operationalized the first gut microbiome and DNA-based weight loss program covered by insurance companies. For personalized guidance to help you navigate your unique biology, metabolism, lifestyle, and food preferences, try a 6-month, customized gut biome and DNA-based weight loss program

Bariatric Surgery Comparison Table Sources: 


Author: Ranjan Sinha

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