Bariatric surgery is a treatment option for people living with obesity when excess weight is significantly affecting health and other approaches have not provided sufficient or sustainable improvement.
The decision to undergo surgery is not based on body weight alone. Doctors may consider body mass index (BMI), obesity-related medical conditions, previous attempts at weight management, overall health, surgical risk and the patient’s ability to commit to long-term follow-up.
In Singapore, BMI thresholds for bariatric surgery are generally lower than conventional international thresholds because Asian populations can develop obesity-related health risks at lower BMI levels. Singapore clinical guidance considers bariatric surgery for people with clinically severe obesity, including those with a BMI above 37.5 kg/m², or above 32.5 kg/m² with obesity-related complications, particularly when these are difficult to control with lifestyle and medication.
For some patients, however, surgery may not be the only procedural option. Endoscopic sleeve gastroplasty (ESG) treatment is a less invasive endoscopic approach that reduces stomach volume without surgically removing part of the stomach. It may be considered for selected patients who do not meet traditional surgical criteria, prefer a non-operative approach or require an alternative based on their health and treatment goals.
What Is Bariatric Surgery?
Bariatric surgery, also called metabolic or weight-loss surgery, refers to procedures that alter the digestive system to help achieve substantial and sustained weight loss.
Common procedures include:
- Sleeve gastrectomy
- Roux-en-Y gastric bypass
- Other procedures in selected patients
Depending on the operation, bariatric surgery can work through several mechanisms, including:
- Reducing the amount of food the stomach can hold
- Changing appetite and satiety signals
- Altering gastrointestinal hormones
- Changing nutrient absorption in certain procedures
Bariatric surgery can also improve obesity-related conditions, including type 2 diabetes and obstructive sleep apnoea.
It should be viewed as part of long-term obesity management rather than a standalone procedure that eliminates the need for lifestyle changes or follow-up.
Why Might Bariatric Surgery Be Recommended?
Bariatric surgery may be considered when obesity has become a significant health concern and non-surgical approaches have not produced sufficient or durable results.
The decision may be influenced by several factors.
1. Your BMI Is Within a Range Where Surgery May Be Considered
BMI is calculated using height and weight and is commonly used as one of the screening measures for obesity.
However, BMI thresholds are not interpreted identically across all populations.
For Asian patients, including those in Singapore, lower BMI thresholds may be used because obesity-related metabolic risks can occur at lower BMI levels. Singapore’s clinical guidance identifies patients with BMI above 37.5 kg/m² as potential candidates for bariatric surgery, while those with BMI above 32.5 kg/m² and obesity-related complications may also be considered.
These numbers should not be treated as an automatic indication for surgery. A specialist assessment is still required.
2. You Have Obesity-Related Health Conditions
The presence of medical conditions associated with obesity can influence the decision to consider surgery.
These may include:
- Type 2 diabetes
- High blood pressure
- Abnormal cholesterol levels
- Obstructive sleep apnoea
- Fatty liver disease
- Cardiovascular disease
- Certain obesity-related joint problems
For example, Singapore’s clinical pathways recognise BMI above 32.5 kg/m² together with obesity-related conditions such as diabetes, hypertension, lipid disorders, fatty liver disease, obstructive sleep apnoea and metabolic syndrome as a setting where bariatric surgery may be considered.
The objective is therefore not simply to reduce weight, but potentially to improve health conditions associated with obesity.
3. Lifestyle Changes Have Not Produced Sufficient Results
Bariatric surgery is generally not considered the first step in weight management.
Patients may previously have tried:
- Dietary changes
- Exercise
- Behavioural modification
- Structured weight-management programmes
- Weight-loss medication
If these approaches have not produced sufficient or durable weight loss, a specialist may discuss procedural options.
The 2022 ASMBS/IFSO guidelines also emphasise metabolic and bariatric surgery as part of comprehensive obesity treatment and recommend multidisciplinary assessment.
This does not mean that a patient has to demonstrate repeated failure with every possible treatment before surgery can ever be discussed. The appropriate pathway depends on the individual’s health, treatment history and clinical circumstances.
4. Your Weight Is Affecting Your Quality of Life
Obesity can affect more than metabolic health.
Excess weight may contribute to difficulties with:
- Walking
- Exercise
- Sleep
- Daily mobility
- Work activities
- Physical independence
Some patients may also experience reduced quality of life because of limitations caused by obesity.
These factors may form part of a broader assessment when considering treatment.
5. Your Health Risks Are Increasing
The decision to consider bariatric surgery may become more important when obesity-related health problems are becoming more difficult to control.
For example, a patient may have:
- Increasing blood sugar levels
- Poorly controlled hypertension
- Worsening sleep apnoea
- Progressive fatty liver disease
- Increasing mobility problems
In these situations, reducing excess weight may form part of a broader strategy to improve health.
Is Bariatric Surgery Recommended Solely Based on BMI?
No.
BMI is useful for determining whether someone falls within a range where bariatric surgery may be considered, but it does not provide a complete picture of health.
A specialist may also assess:
- Waist circumference or central adiposity
- Metabolic health
- Obesity-related complications
- Previous weight-management efforts
- Eating patterns
- Psychological wellbeing
- Surgical risk
- Ability to participate in long-term follow-up
This is particularly relevant in Asian populations, where metabolic complications may develop at lower BMI levels.
What Happens Before Bariatric Surgery Is Recommended?
Bariatric surgery should generally involve more than a single consultation with a surgeon.
Singapore’s Ministry of Health guidance recommends that bariatric surgery be delivered through a multidisciplinary programme, involving appropriate healthcare professionals such as surgeons, dietitians, physicians, psychologists and other allied health professionals.
An assessment may therefore include several components.
1. Medical Assessment
Your doctor may review:
- Existing medical conditions
- Medication use
- Previous operations
- Blood pressure
- Blood sugar
- Other obesity-related health risks
Additional tests may be recommended depending on your health.
2. Nutritional Assessment
A dietitian may assess:
- Eating habits
- Portion sizes
- Meal patterns
- Nutritional deficiencies
- Previous dieting attempts
This can also help patients understand the dietary changes required after surgery.
3. Psychological Assessment
Weight management can involve behavioural and psychological factors.
Assessment may help identify:
- Eating behaviours
- Mental health concerns
- Expectations about surgery
- Ability to maintain long-term lifestyle changes
An uncontrolled psychological disorder or active substance abuse may be a contraindication to bariatric surgery and may require appropriate treatment before surgery is considered.
4. Surgical Risk Assessment
The surgical team will assess whether the patient is medically fit for the proposed procedure.
Factors may include:
- Heart health
- Lung function
- Previous abdominal surgery
- Anaesthetic risk
- Existing medical conditions
Some conditions may require optimisation before surgery.
5. Discussion of Long-Term Follow-Up
Bariatric surgery requires ongoing follow-up.
Patients should understand that surgery does not eliminate the need for:
- Healthy eating
- Physical activity
- Nutritional monitoring
- Medical reviews
- Weight monitoring
Long-term management is an important part of maintaining the benefits of treatment.
When Might Bariatric Surgery Not Be Appropriate?
Not everyone with obesity is suitable for surgery.
A specialist may recommend delaying or avoiding surgery when:
- Surgical risks are unacceptably high
- A medical condition requires optimisation first
- There is an uncontrolled psychological disorder
- There is active substance abuse
- The patient is unable to commit to necessary follow-up
- Another treatment approach is more appropriate
Pregnancy and active malignancy are also listed as contraindications in Singapore’s obesity clinical practice guidance.
These considerations are assessed individually rather than applied as a simple checklist.
What Is ESG Treatment?
Endoscopic sleeve gastroplasty (ESG) is an endoscopic treatment for obesity that reduces the size and capacity of the stomach using an endoscope and internal sutures.
Unlike surgical sleeve gastrectomy:
- No part of the stomach is surgically removed
- The procedure is performed through the mouth using an endoscope
- The stomach is remodelled to create a smaller gastric volume
ESG is therefore different from bariatric surgery, although both are procedural treatments for obesity.
The American Society for Metabolic and Bariatric Surgery describes ESG as an endoscopic option for carefully selected patients within a comprehensive, multidisciplinary obesity programme. It does not consider ESG equivalent to metabolic and bariatric surgery in terms of expected weight loss or metabolic effect.
Who May Consider ESG Treatment?
ESG may be discussed for selected adults who:
- Have obesity
- Have not achieved adequate weight loss with lifestyle measures and, where appropriate, medication
- Prefer a non-operative procedural approach
- May not be suitable for or may not wish to undergo bariatric surgery
The ASMBS notes that ESG is primarily considered in the BMI range of 30 to 40 kg/m², although there may be a role outside this range depending on the patient’s clinical circumstances.
The 2024 ASGE-ESGE guideline suggests endoscopic bariatric and metabolic therapies alongside lifestyle modification for adults with BMI ≥30 kg/m², or BMI 27.0 to 29.9 kg/m² with at least one obesity-related comorbidity.
Eligibility can differ between centres, so patients should undergo individual assessment rather than using BMI alone to determine suitability.
Bariatric Surgery vs ESG Treatment: What Is the Difference?
| Bariatric Surgery | ESG Treatment | |
| Type | Surgical procedure | Endoscopic procedure |
| Access | Surgical access to the digestive system | Endoscope passed through the mouth |
| Stomach tissue removed | Depending on procedure, yes | No |
| Examples | Sleeve gastrectomy, gastric bypass | Endoscopic sleeve gastroplasty |
| Typical role | Often used for more severe obesity and/or obesity-related disease | Option for selected patients with obesity seeking a non-operative procedure |
| Anaesthesia | Requires surgical anaesthesia | Performed endoscopically under appropriate sedation/anaesthesia |
| Long-term follow-up | Required | Required |
| Lifestyle changes | Still necessary | Still necessary |
The choice between these approaches depends on factors including BMI, obesity-related conditions, previous treatment, procedural risk, patient preferences and expected treatment effect.
Is ESG a Replacement for Bariatric Surgery?
Not necessarily.
ESG and bariatric surgery have different mechanisms, risks, expected weight-loss outcomes and metabolic effects.
For some patients, ESG may be an alternative to surgery. For others, bariatric surgery may provide a more appropriate level of treatment based on the severity of obesity or associated medical conditions.
The ASMBS specifically notes that ESG should not be considered equivalent to metabolic and bariatric surgery in expected weight loss or metabolic impact.
What Are the Most Common Bariatric Surgery Options?
If surgery is appropriate, the surgeon may discuss different procedures.
Sleeve Gastrectomy
Sleeve gastrectomy removes a substantial portion of the stomach, leaving a smaller stomach in the shape of a sleeve.
It can reduce stomach capacity and influence appetite-related signals.
Gastric Bypass
Roux-en-Y gastric bypass creates a smaller stomach pouch and reroutes part of the small intestine.
It therefore affects both food intake and nutrient absorption.
The choice of procedure depends on the patient’s health, treatment goals and surgical assessment.
What Happens If You Are Recommended for Bariatric Surgery?
Once a patient has been assessed as suitable, the surgical team will discuss:
- The recommended procedure
- Expected weight loss
- Potential benefits
- Risks and complications
- Preparation
- Recovery
- Dietary changes
- Long-term monitoring
Patients should have an opportunity to ask questions before deciding whether to proceed.
What Are the Long-Term Considerations After Bariatric Surgery?
Bariatric surgery is not the end of obesity treatment.
Long-term care may involve:
Nutritional Monitoring
Some procedures can affect nutrient intake or absorption. Patients may require supplements and periodic blood tests.
Dietary Changes
Portion sizes and food choices typically need to change after surgery.
Physical Activity
Regular physical activity supports long-term weight management and general health.
Monitoring Weight Changes
Weight loss and potential weight regain may be monitored over time.
Management of Obesity-Related Conditions
Doctors may reassess conditions such as:
- Diabetes
- Hypertension
- Sleep apnoea
- Fatty liver disease
Medication requirements may change as health improves.
Bariatric surgery may be recommended for selected patients with clinically significant obesity, particularly when excess weight is associated with health problems and lifestyle or medical treatments have not produced sufficient or sustainable results.
In Singapore, BMI thresholds are adjusted for Asian populations, with local clinical guidance identifying BMI above 37.5 kg/m², or above 32.5 kg/m² with obesity-related complications, as situations where bariatric surgery may be considered. However, BMI is only one part of the assessment.
For patients who may not require or prefer not to undergo surgery, ESG treatment may provide another procedural option. ESG is performed endoscopically and reduces stomach volume without surgically removing part of the stomach. Its suitability depends on individual factors, and it should not be considered equivalent to bariatric surgery in terms of expected weight loss or metabolic effects.
Ultimately, the decision should be made through a multidisciplinary assessment that considers BMI, obesity-related conditions, previous treatment, overall health, surgical risk, patient preferences and the need for long-term follow-up.
This article is for general information only and should not replace medical advice from a qualified healthcare professional.
