What is Postbariatric Surgery Hypoglycemia?
Obesity, a common and often recurring condition, is characterized by an excessive amount of fat stored in the body. The World Health Organization (WHO) classifies someone as obese if their body mass index (BMI) is 30 or higher, and labels severe obesity as a BMI of 40 or higher. BMI is simply a formula that uses your weight and your height to calculate the amount of body fat you have.
Recent data from the National Nutritional Health and Examination Survey (NHANES) shows that about 19.7% of children and teens aged 2 to 19 are obese. Among adults aged 20 and older, the rate of obesity is 41.9%, while severe obesity is at a rate of 9.2%. It’s important to note that obesity increases the risk of diseases like type 2 diabetes, fatty liver disease, high blood pressure, heart disease, stroke, dementia, sleep apnea, arthritis, and certain mood disorders. The Centers for Disease Control and Prevention (CDC) estimates that medical care costs related to obesity were about $173 billion in 2019 alone.
Bariatric surgery, a weight-loss surgery, has helped patients with severe obesity lose more significant amounts of weight than non-surgical treatments. The number of these surgeries has been increasing every year from 2011 through 2019. Therefore, it’s important to also be alert to potential complications after the surgery.
One increasingly common complication after bariatric surgery is hypoglycemia, which is generally characterized by low blood sugar levels after a meal in individuals who have had weight loss surgery. These episodes can be detected using techniques like continuous glucose monitoring (CGM). Most often, this problem comes up after a type of surgery called Roux-en-Y gastric bypass (RYGB), but it can also occur after other types of weight-loss surgeries, like sleeve gastrectomy (SG) and laparoscopically adjustable gastric band (LAGB).
What Causes Postbariatric Surgery Hypoglycemia?
The cause of this condition is thought to be linked to changes in the body’s structure following surgery, how quickly food passes through the system, and patterns of hormones and blood sugar levels. Eating large meals made mostly of simple sugars and refined fats often makes these effects worse.
Scientists have also recently found that the body’s ability to regulate blood sugar levels when fasting is often impaired, although they’re not sure yet why this happens.
Risk Factors and Frequency for Postbariatric Surgery Hypoglycemia
The risk of low blood sugar (hypoglycemia) after weight loss surgery (bariatric surgery) is linked to being female, having had a specific type of surgery called Roux-en-Y gastric bypass (RYGB), more time passed since surgery, and not having diabetes before the surgery. It’s important to know that 70% to 80% of people undergoing this type of surgery are women.
Research has shown that there is no significant difference in the chance of having low blood sugar after two types of surgery; Sleeve Gastrectomy (SG) and RYGB. However, RYGB might lead to more severe low blood sugar episodes. Nighttime and symptomless low blood sugar is more common after SG surgery, while low blood sugar after meals is more common with RYGB.
The reported rates of low blood sugar after weight loss surgery can vary greatly. This might be due to differences in research methods, variability in testing, and the definitions of what counts as low blood sugar. There is increasing awareness of conditions such as symptomless and meal-independent hypoglycemia, and the use of more sensitive testing methods have highlighted that this condition might be more common than we think.
When patients were asked to recall symptoms, studies found that low blood sugar after meals was reported in anywhere from 0.1% to 34% of patients. In a research study using a specific test (OGTT), it was reported in 25.6% of patients. Other studies using more delicate techniques reported low blood sugar in 55% to 75% of the patients in the study.
There’s still a lot we don’t know about the true impact of this condition and the factors that increase the risk. More extensive research is needed to understand this better.
Signs and Symptoms of Postbariatric Surgery Hypoglycemia
People who suffer from late dumping syndrome can experience certain symptoms months or years after surgery. These symptoms usually appear 1 to 3 hours after eating, especially if the meal was large and high in simple carbohydrates. There are two main types of symptoms: autonomic and neuroglycopenic.
- Autonomic symptoms relate to the nervous system and include feelings of anxiety, sweating, trembling, and heart palpitations.
- Neuroglycopenic symptoms are tied to low blood sugar and can cause confusion, fatigue, lightheadedness, slurred speech, blurred vision, and disorientation. In severe cases, people may have seizures or fall into a coma.
After an operation called Roux-en-Y gastric bypass (RYGB), it’s more common to have low blood sugar after meals. However, after a sleeve gastrectomy, it’s more common to have low blood sugar that isn’t tied to meals. But both types of low blood sugar can happen after either surgery, and some people have both types. In some cases, people who have repeated episodes of low blood sugar may not have early warning symptoms. This is known as hypoglycemia unawareness. They might only notice the problem when they start having neuroglycopenic symptoms.
There aren’t any physical signs specific to this condition that would show up during a doctor’s examination.
Testing for Postbariatric Surgery Hypoglycemia
There is currently no exact standard for diagnosing postprandial hyperinsulinemic hypoglycemia, a condition where low blood sugar occurs after a meal, especially in patients who’ve undergone bariatric surgery (weight loss surgery). This is due to the variety of symptoms and various definitions of hypoglycemia, which is the term for low blood sugar.
According to the International Hypoglycemia Study Group, a glucose level less than 3.0 mmol/L (or less than 54 mg/dL) suggests hypoglycemia is likely.[19]
The American Society for Metabolic and Bariatric Surgery (ASMBS) suggests diagnosing postprandial hyperinsulinemic hypoglycemia, also referred to as late dumping syndrome, if a patient experiences the following:
- Symptoms manifest more than one year after surgery
- Normal fasting glucose and insulin levels
- Symptoms align with hypoglycemia and disappear as the hypoglycemia resolves
- A positive result on the provocative test.
In addition to these tests, some professionals suggest checking if a patient has high insulin levels at the same time as low blood sugar after they’ve had a mixed meal.[20]
Testing for this includes the oral glucose tolerance test (OGTT) and the mixed meal tolerance test (MMTT). However, these methods are challenged by limitations that the OGTT might not be well tolerated because of the large amount of sugar it requires and can cause severe low blood sugar, while the MMTT remains controversial.
A promising alternative could be Continuous Glucose Monitoring (CGM), which more accurately tracks shifts in blood sugar levels while allowing patients to continue their regular meals. There are added advantages of identifying hypoglycemia that isn’t causing symptoms and episodes of fasting hypoglycemia.
In cases where fasting triggers hypoglycemia, it’s important to evaluate the patient for insulinoma, a condition where the pancreas produces too much insulin. Evaluations can involve invasive studies, computerized tomography (CT) scans, magnetic resonance imaging (MRI), or blood tests after a 72-hour fasting test.[3]
It is critical to recognize the various symptoms and patterns of hypoglycemia and order appropriate tests. Moreover, certain conditions like insulinoma, problems with adrenal gland function, liver dysfunction, and medications that can lower blood sugar levels should be ruled out based on the patient’s medical history and physical examination.
Lastly, a table illustrating the varying lab results of several conditions causing hypoglycemia can help doctors differentiate between them.
Treatment Options for Postbariatric Surgery Hypoglycemia
Medical nutritional therapy is a primary strategy for managing various health conditions. The diet typically recommended includes eating small amounts of carbohydrates that are slow to raise your blood sugar (low glycemic index carbohydrates), getting adequate protein, eating moderate amounts of healthy fats, and spacing meals 3 to 4 hours apart. It is also advised to avoid alcohol and caffeinated drinks with meals.
The reason for avoiding foods that quickly raise blood sugar (high glycemic index foods) is that they can lead to a sudden increase in glucose levels which can release excessive insulin and cause a significant drop in blood sugar after eating. Foods with a low glycemic index, on the other hand, are digested more slowly and result in a gradual rise in glucose levels.
If symptoms can’t be controlled with nutritional therapy alone, medication might be an option, although more research is needed in this area. The decision to use medication will depend on the doctor’s expertise and on patient preference. Several medications, including nifedipine, acarbose, GLP-1 analogs, diazoxide, and somatostatin analogs, have been used in treatment according to individual patient reports and small studies.
Acarbose is an enzyme inhibitor that delays the digestion of carbohydrates, which can help control sudden spikes in glucose levels after meals. Diazoxide inhibits insulin secretion, whereas somatostatin analogs slow down the digestion process, affecting the release of several hormones. Calcium channel blockers work on the cells that produce insulin in the pancreas. Usually, experts recommend trying acarbose first, and if it isn’t effective, trying somatostatin analogs.
Aside from medication and dietary therapy, certain surgical procedures may be considered for patients experiencing more severe symptoms. Currently, large-scale trials are yet to be conducted to compare effectiveness and safety of different surgical approaches. Possible surgical procedures that have been reported in small case series include the placement of a gastrostomy tube in the remnant stomach as well as surgeries that limit the stomach’s outlet, reverse RYGB or convert RYGB to SG. A partial pancreatectomy, which involves removal of part of the pancreas, has been performed but has not been found effective and is not recommended by the ASMBS.
What else can Postbariatric Surgery Hypoglycemia be?
If a person is showing symptoms of low blood sugar (hypoglycemia), there are several possible medical conditions that a doctor might consider as a cause. Remember, a differential diagnosis is the process by which a doctor rules out or determines the most probable disease or condition that could be causing a patient’s symptoms. Some possible causes of hypoglycemia are:
- An insulinoma, which is a tumor in the pancreas that produces too much insulin
- Nonalcoholic fatty liver disease (NAFLD), which has been associated with low blood sugar levels after meals (postprandial hypoglycemia). Obesity can increase the risk of developing NAFLD
- Use of insulin or medication that stimulates your body to produce more insulin (secretagogues). In this situation, a test measuring C peptide levels can help figure out if these are the cause- levels would be low with exogenous (from outside the body) insulin use, but normal or high with the use of secretagogues
- In certain circumstances, the doctor might also consider hormone deficiencies, autoimmune conditions, or tumors not related to the islet cells in the pancreas
All of these possible causes would be considered, tested for, and then either ruled out or confirmed in making a final diagnosis.
What to expect with Postbariatric Surgery Hypoglycemia
Patients with mild to moderate symptoms often find relief through nutritional therapy. However, there is a limited amount of information available regarding the percentage of patients who require medication after undergoing weight loss surgery and experiencing low blood sugar. Additionally, it’s uncertain how many of these patients then need further surgery if their medication doesn’t work, and how many still have symptoms even after having more surgery.
In a recent study reviewing past cases of patients who still had low blood sugar after weight loss surgery and did not find relief from nutritional therapy, the study determined that a medication was effective if it reduced hypoglycemic (low blood sugar) symptoms by more than half and had little to no hypoglycemic events. The study found that medication was overall effective for 45% to 80% of patients. Around 20% of patients needed surgical treatment because less invasive treatments weren’t working. Of these patients, 63% reported that their symptoms were entirely gone after surgery, while 16% reported that their symptoms were 50% to 100% better. Unfortunately, around 21% of people reported no noticeable improvement. The study found that different surgical procedures had different levels of success. However, more research is needed to make conclusive statements. Unresolved symptoms can greatly impact a patient’s quality of life.
Possible Complications When Diagnosed with Postbariatric Surgery Hypoglycemia
Severe low blood sugar, or hypoglycemia, can cause symptoms such as anxiousness, irritability, unclear speech, shakiness, confusion, restlessness, seizures, fainting, and even death.
If you frequently experience episodes of low blood sugar, you may have a condition called “hypoglycemia unawareness.” This means that even when your blood sugar level is low, your body doesn’t respond normally, and the symptoms of low blood sugar become less noticeable over time. Research on patients who have undergone weight-loss surgery has shown that low blood sugar can reduce their ability to drive safely, even when they don’t show typical low blood sugar symptoms.
For people with diabetes, low blood sugar can gradually harm various organs in the body, seriously impacting their quality of life. However, the long-term effects of low blood sugar after weight-loss surgery are still unknown.
Common Symptoms of Severe Hypoglycemia:
- Anxiety
- Irritability
- Slurred speech
- Shakiness
- Disorientation
- Agitation
- Seizures
- Loss of consciousness
- Potential death
Preventing Postbariatric Surgery Hypoglycemia
The reasons why some people develop low blood sugar after weight loss surgery aren’t fully clear, meaning we need more information to better understand who is at risk. If you’re thinking about having surgery to lose weight, you should know about the possibility of experiencing low blood sugar afterward, how this might affect your quality of life, and what treatments are available.
Avoiding big meals that contain a lot of simple sugars (like sweets) and instead eating smaller, more frequent meals rich in protein, healthy fats, like avocados and nuts, and fiber found in fruits and vegetables, could help manage the symptoms. If changes in diet don’t help, medication can be considered. In some cases, if other methods don’t work, additional surgery might be needed to treat this condition.
