Ranjan Sinha

January 11, 2020

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

Millions of Americans struggle with obesity, and despite hard work on diet, and exercise, many are still unable to achieve a healthy weight. Some, after exhausting all other options, opt to undergo bariatric surgery.

A surgical approach to weight loss is far from a quick fix. Bariatric surgery comes with a unique set of pros and cons. Understand your surgical weight loss options and how they might affect your health and gut microbiome, before you even meet with a surgeon. What is Bariatric Surgery?

Bariatric surgery refers to gastric bypass and other weight-loss surgeries wherein a gastric bypass surgeon surgically alters the digestive system to help patients lose weight and prevent the onset of or reduce symptoms of pre-existing obesity-related 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

Each type of surgery comes with advantages and disadvantages, which can be discussed thoroughly with a physician.

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. Or a BMI above 35 (class 2 obesity) and at least one obesity-related core morbidity;
  3. Or 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

Learn about the details for each type of bariatric surgery to learn the pros and cons of each, so that 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.
**Currently 1% of bariatric surgeries performed in the U.S. employ gastric bands because this type of operation is unable to leverage the additional power of hormonal changes to stymie weight gain.

The sleeve gastrectomy - with a mortality rate of 0.08% within 30 days after the procedure and less than 1% of patients ending up with serious complications - is the safest of the procedures.

Does Insurance Cover Weight Loss Surgery?

An invasive procedure such as bariatric surgery is expensive, so patients often ask if their health insurance provider will cover the procedure. In many cases, bariatric surgery can be covered by insurance with pre-approval. Coverage varies for patients and providers. For example, Medicare covers gastric bypass and laparoscopic gastric banding when patients meet certain criteria. Insurers often includes weight loss surgeries at designated facilities in its healthcare plans.

Weight Loss After Bariatric Surgery?

Most patients begin losing weight days after the procedure. Those who undergo a bariatric surgery must follow a strict, high-protein, low-sugar, low-fat diet. Physicians project weight loss goals to be achieved within about 12 to 18 months after the procedure, at which point, weight loss often plateaus and many patients even begin to regain weight. The most important mechanism for weight loss for gastric sleeve and gastric bypass surgeries is that they cause changes that affect hormones involved with eating (such as gherlin and leptin). Thus, in addition to having a smaller stomach, these hormonal changes will result in post-surgical patients having smaller appetites.

The Effects of Bariatric Surgery on Gut Microbiome?

Following bariatric surgery, some notable changes take place within the gut microbiome that are likely due to four major factors:

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

In essence, the dietary changes following the surgery play a role in changes to the patient’s gut microbiota composition. Moreover, when the volume of the stomach decreases, the pH increases and this basic environment 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, these changes to the gut microbiome composition play a key role in the effectiveness of bariatric surgery.

Is Bariatric Surgery Safe?

In short, yes. Bariatric surgeries, when done at a high volume center of excellence, have an average mortality rate of 0.93% or less, and are safer than even having your gallbladder and appendix. Still, as with all major invasive procedures, there are a number of common, as well as 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 that subtype of weight-loss surgery.

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

The truth about obesity is that genetics and gut microbiome are central to body weight, and every human body is unique. For a complete picture of health and high BMI, weight loss patients should inquire about DNA and gut microbiome sampling.

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

Some large insurance companies in 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, and PCOS .

Final Thoughts

Bariatric surgery is an effective weight-loss method, but every procedure comes with risks. Surgical complications, while rare, are still a 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.

When compared to other, non-surgical weight loss procedures, bariatric surgery can produce greater long term weight loss and diabetes remission...changes that are usually able to be maintained, at least in part, for long term. If bariatric surgery ends up being the right option for your health, gut-microbiome and DNA-based programs may further the efficacy of the procedure as well.

Bariatric Surgery Comparison Table Sources:

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