Who Is Eligible for Gastric Sleeve Surgery?

Most patients presenting for bariatric surgery assume that the eligibility assessment rests on a single number. The assessment does begin with body mass index; it does not, however, rest on that criterion alone.

1. Body Mass Index: Definition and Limitations

Body mass index (BMI) is calculated by dividing weight by height in metres squared. According to the World Health Organization classification:

• Below 18.5: Underweight
• 18.5–24.9: Normal
• 25–29.9: Overweight
• 30–34.9: Obesity, class I
• 35–39.9: Obesity, class II
• 40 and above: Obesity, class III (severe obesity)

BMI is a screening criterion, not a diagnostic tool. It does not account for muscle mass, fat distribution, age or coexisting conditions. It may read misleadingly high in individuals undertaking regular resistance exercise, and misleadingly low in older individuals with sarcopenia. It remains the starting point in guidelines owing to its calculability and comparability.

You can determine your own value using our BMI calculator.

2. Thresholds Defined in Guidelines

• BMI 40 and above: Considered eligible for surgical assessment without requiring an associated condition.
• BMI 35–39.9: Considered in the presence of an obesity-related comorbidity such as type 2 diabetes, hypertension, obstructive sleep apnoea, non-alcoholic fatty liver disease or degenerative change in weight-bearing joints.
• BMI 30–34.9: In current guidelines, metabolic surgery may be considered, particularly in cases accompanied by uncontrolled type 2 diabetes.

Important Note: These values are thresholds for assessment, not for operating. The distinction is decisive for clinical decision-making.

3. Criteria Assessed Beyond Body Mass Index

• History of weight-loss attempts: The presence and outcome of a serious attempt involving dietary modification and physical activity are established. Surgery is not a first-line treatment.
• Status of comorbidities: The duration of diabetes and the level of glycaemic control affect the metabolic response expected from surgery.
• Eating behaviour: Binge eating disorder, night eating syndrome or habitual consumption of high-calorie liquids should be addressed preoperatively. Gastric volume is reduced; behaviour does not change of its own accord.
• Adherence to follow-up: Sleeve gastrectomy requires lifelong clinical follow-up and vitamin supplementation.
• Presence of gastro-oesophageal reflux: In patients with significant reflux and hiatal hernia, sleeve gastrectomy may exacerbate symptoms; alternative procedures are considered in such cases.

4. Situations Where Surgery Is Unsuitable or Deferred

• Untreated severe psychiatric illness
• Active substance or alcohol use disorder
• Cardiac and pulmonary disease raising operative risk to an unacceptable level
• Pregnancy and plans for pregnancy in the near term

A proportion of these are matters of timing rather than permanent contraindications.

5. What Is Sleeve Gastrectomy?

In sleeve gastrectomy, a substantial portion of the stomach along the greater curvature is removed, leaving a narrow tubular stomach. The mechanism of action is twofold:

• Restrictive effect: The volume of food that can be taken in is reduced.
• Hormonal effect: Appetite decreases because the gastric segment secreting hormones involved in hunger regulation is removed.

The procedure is performed laparoscopically. As intestinal continuity is not altered, malabsorption is limited compared with gastric bypass; vitamin and mineral monitoring remains necessary.

6. Is Surgery Sufficient on Its Own?

No. Sleeve gastrectomy is a tool that makes weight loss achievable; what sustains the process is the patient's dietary pattern, physical activity and continuity of follow-up. The first postoperative year is the period of most rapid weight loss; durability is determined by the behavioural pattern of subsequent years.

For this reason assessment is not confined to surgery; a dietitian, endocrinology and, where required, psychiatry are involved in the process.

7. Considerations for Patients Travelling from Abroad

For patients planning surgery in Turkey, the aspect warranting greatest attention is not the procedure itself but the postoperative period. The arrangements for follow-up after return, the point of contact in the event of a complication and the recommended duration of stay before air travel should be clarified in advance. A plan concluding at discharge is not a complete plan.

8. Possible Risks

As with any surgical procedure, sleeve gastrectomy carries risks. Patients should understand them before surgery.

• Leak: Leakage from the staple line. Uncommon, but the most serious early complication; early diagnosis is decisive.
• Bleeding and thromboembolism: Risk is reduced by early mobilisation and preventive treatment.
• Reflux: May appear after surgery, or existing reflux may worsen.
• Vitamin and mineral deficiencies: Prevented by regular blood tests and supplementation.
• Weight regain: In the long term, depends on sustaining eating habits.

See the risk section of our bariatric surgery page for further detail.

Frequently Asked Questions

Can a sleeve be performed if my BMI is below 35?

In the BMI 30–35 range, metabolic surgery may be considered in current guidelines, particularly where type 2 diabetes is not controlled on medication. Without an associated condition, surgery is generally not the first option; non-surgical methods may be considered.

Can sleeve gastrectomy be reversed?

No. Because part of the stomach is removed, the procedure cannot be reversed. The decision is therefore made after detailed assessment and once the patient fully understands the process.

What tests are done before surgery?

Blood tests, upper endoscopy, abdominal ultrasound and, where needed, cardiac and respiratory assessment. Dietetic assessment and, where needed, psychological assessment are also part of the process.

Is sleeve surgery performed over the age of 65?

Age alone is not an absolute barrier. In older patients the decision is made by carefully weighing general health, coexisting conditions, and the expected benefit against the risks.

Conclusion

Body mass index is a starting point, not a decision. Being above the threshold does not demonstrate that surgery is appropriate; remaining somewhat below it does not mean exclusion at the outset. The decision follows from examination, laboratory and imaging investigations, and assessment of comorbidities together.

References

• Eisenberg D, Shikora SA, Aarts E, et al. 2022 American Society for Metabolic and Bariatric Surgery (ASMBS) and International Federation for the Surgery of Obesity and Metabolic Disorders (IFSO): Indications for Metabolic and Bariatric Surgery. Surgery for Obesity and Related Diseases, 2022.
• World Health Organization. Obesity and overweight — Fact sheet.
• Mechanick JI, Apovian C, Brethauer S, et al. Clinical Practice Guidelines for the Perioperative Nutrition, Metabolic, and Nonsurgical Support of Patients Undergoing Bariatric Procedures — 2019 Update. Surgery for Obesity and Related Diseases, 2020.