Gastric bypass surgery and diabetes: what you need to know

Gastric bypass surgery is a type of surgery often recommended for people who need to lose significant weight for health reasons.

A doctor may recommend gastric bypass surgery for people with diabetes to prevent heart disease, lower high blood pressure, help with weight loss, and in some circumstances reverse type 2 diabetes.

In this article, we will explore gastric bypass and other weight loss surgeries and the benefits these procedures can bring to people living with diabetes.

What is gastric bypass surgery?

Gastric bypass is a common type of weight loss surgery, also known as bariatric surgery. A gastric bypass procedure involves remodeling the stomach and small intestine so that food passes through the digestive system in a different way.

The surgery causes the food to “bypass” the stomach and go to the intestines instead.

There are several effects of this diversion in food and restructuring of the digestive system.

First, because a larger stomach is not the first stop for food, most people feel full sooner after gastric bypass surgery. This means that a person cannot eat as much food after surgery, and most people report feeling full for longer after a meal.

Second, because the food you eat also bypasses the part of the digestive system that absorbs nutrients, fewer calories are absorbed, which further aids in the weight loss process.

This also means that fewer micronutrients are absorbed, so people who are undergoing gastric bypass surgery are typically prescribed a daily vitamin regimen to supplement what is no longer being absorbed through diet alone.

The most common type of gastric bypass surgery is the Roux-en-Y procedure (named after the surgeon who invented it, César Roux) and the way the stomach and small intestine are joined together in a new “Y” shape.

According to the University of California, Los Angeles School of Medicine, gastric bypass surgeries have good short-term and long-term weight loss results.

In the short term, most patients can expect to lose 60% – 80% of their excess weight. In the long term, most patients are at least half overweight.

Gastric bypass surgeries are also generally effective in helping people avoid complications related to being overweight or obese for an extended period of time.

These procedures are not for everyone. Gastric bypass is usually recommended by a doctor only if a person’s body mass index (BMI) is 40 or higher, or if a BMI is over 35 and occurs at the same time as certain serious weight-related diagnoses.


Can a person with diabetes have gastric bypass surgery?
Yes, people with diabetes can have gastric bypass surgery if recommended by their doctor or other healthcare provider.
In general, gastric bypass surgery is only recommended for adults with type 2 diabetes when they have a BMI over 35 and when weight cannot be controlled with diet, exercise and medication alone.
There are also cases where gastric bypass surgery may be recommended even if the person’s weight or BMI alone does not normally meet common medical standards.  These may include if a person’s blood sugar (as measured by HbA1c) is well out of range and is difficult or impossible to control with medication, diet and exercise.
If a person has serious complications from type 2 diabetes and the doctor assesses that significant weight loss is necessary, gastric bypass may also be the preferred medical intervention.
According to the American Academy of Pediatrics, there are also some limited circumstances where teens over the age of 13 with clinical obesity and conditions such as type 2 diabetes may benefit from weight loss surgery such as gastric bypass.

How does gastric bypass surgery affect diabetes?
The main purpose of gastric bypass surgery is to help people lose weight and avoid complications from prolonged periods of being overweight or obese.
Clinical studies have long shown that as body fat and BMI increase, so does insulin resistance. 
Since gastric bypass surgeries help most people lose weight quickly, insulin resistance, which is a hallmark of type 2 diabetes, is generally improved with this procedure.
In addition, according to a study published in the Journal of Clinical Endocrinology & Metabolism, nearly 60% of adults with type 2 diabetes who underwent gastric bypass surgery experienced long-term remission.
Fewer people had to take long-acting or mealtime insulin after gastrectomy and weight loss, and about half of people who previously had type 2 diabetes will reach normal, ‘non-diabetic’ blood sugar levels as measured by A1c.
While full weight loss after surgery may take 12 to 24 months, the effects on blood sugar levels can be much faster.
A significant proportion of people with type 2 diabetes will experience near-normal blood sugar levels within a few days after gastric bypass surgery, although this is likely partly due to the calorie-restricted diet required during the postoperative recovery period. 

What are the risks of bariatric surgery for diabetes?
Although gastric bypass itself is one of the safest surgeries and has great potential to help people lose weight, all bariatric surgeries carry some risk.
Some of the potential complications of weight loss surgery include:

Prolonged nausea and vomiting
Acid reflux (heartburn) and gastroesophageal reflux disease (GERD)
Postoperative infections
Malnutrition
Stomach or bowel obstruction 
Inability to eat certain foods

There are other changes that especially people with diabetes should be aware of if they are undergoing gastric bypass surgery.
One complication to be aware of is an increased risk of hypoglycemia, or low blood sugar.
Because the stomach is functionally smaller after a gastric bypass, people taking insulin should be careful if their blood sugar is low.  In the event of low blood sugar after surgery, some people with diabetes have reported finding it more difficult to consume enough carbs/sugar to bring their blood sugar back to normal levels quickly.
Because gastric bypass and other bariatric procedures can also cause nausea and vomiting, it’s important for people using insulin to be aware of their blood sugar levels and avoid overdosing in case it becomes difficult to finish a meal or keep food down.
This is especially important soon after the procedure, while getting used to the amount of food needed to feel full and the body’s reaction to food.
A very small percentage of people also experience repeated, severe low blood sugar levels as a side effect of gastric bypass surgery. 
For most people who are prescribed a gastric bypass by their doctor, the risk of complications is relatively small compared to the risk of being significantly overweight for a long time.
Before undergoing gastric bypass surgery, it is important to talk to your doctor and healthcare team about how to manage your diabetes before and after surgery and whether there are specific changes to your medications, diet or exercise that will be needed to make the procedure effective and reduce risk of complications.

What is the best weight loss surgery for diabetes?
There are many different types of weight loss surgery.  In the United States and Europe, the three most common types of weight loss surgery are gastric bypass, adjustable gastric banding (also known as a “hip band”), and sleeve gastrectomy procedures.
There are advantages and disadvantages to each type of surgery, and your doctor may recommend one of many clinical reasons.  
Clinical studies have consistently shown that gastric bypass is safe, well-tolerated, and effective in helping people with type 2 diabetes lose excess weight and avoid complications. 
For this reason, gastric bypass surgery is the most common bariatric procedure recommended for people with type 2 diabetes.
Recent research has also shown that another, less common surgical procedure known as bile-pancreatic diversion may be even more effective in some people with diabetes.  This is because the biliary pancreatic diversion procedure helps people become more insulin sensitive than other weight loss surgeries.
However, gastric bypass surgery has fewer potential complications, has a long history, and has a good safety profile.  For this reason, most doctors recommend gastric bypass for people with diabetes who need surgery to help them lose weight and improve their diabetes control. 
Your doctor or health care provider can discuss all the surgical and non-surgical options available to you and will be able to explain why they recommend a particular course of action.  

Frequently asked questions

What are the Different Types of Gastric Bypass Surgery? 
There are four main types of gastric bypass surgery.  Gastric bypass, Roux-en-Y (RYGB, proximal) is the most common.  There are also Roux-en-Y distal procedures, as well as mini gastric bypass and endoscopic duodenojejunal bypass, which are still being evaluated in clinical trials.

Does diabetes go away after gastric bypass? 
Nearly 60% of adults with type 2 diabetes who underwent gastric bypass surgery experienced long-term remission of their diabetes.

Can you take metformin if you’ve had a gastric bypass? 
Metformin may still be prescribed after gastric bypass surgery, but studies have shown that its absorption and effectiveness may be altered, so it’s likely your doctor will adjust your dose.