Obesity has emerged as a major global public health crisis, recognized as a complex, multifactorial chronic disease. It is characterized by the excessive accumulation of body fat to the extent that it may impair health. While lifestyle modifications including diet and exercise remain cornerstone therapies, for individuals with severe obesity, known as morbid obesity, these methods often prove insufficient for achieving and maintaining significant, long-term weight loss and resolving associated health complications. In such cases, surgical intervention, specifically bariatric and metabolic surgery, is a highly effective treatment option.
Definition and Epidemiology of Obesity
Obesity is defined clinically as an abnormal or excessive fat accumulation that presents a risk to health. It is not merely a cosmetic concern but a profound health problem associated with numerous debilitating and life-threatening conditions, often referred to as comorbidities of obesity. These include Type 2 Diabetes Mellitus, hypertension, dyslipidemia, cardiovascular disease, stroke, sleep apnea, non-alcoholic fatty liver disease (NAFLD), osteoarthritis, certain types of cancer, and psychological issues such as depression.
The epidemiology of obesity is alarming. Over the past few decades, its prevalence has dramatically increased worldwide, reaching epidemic proportions. According to the World Health Organization (WHO), in 2016, more than 1.9 billion adults aged 18 years and older were overweight, and over 650 million were obese. This represents 39% of adults being overweight and 13% being obese globally. The trend continues to rise, impacting individuals across all age groups, socioeconomic statuses, and geographic regions. The increasing burden of obesity places significant strain on healthcare systems globally due to the management costs of associated comorbidities.
Body Mass Index (BMI) and Classification
Body Mass Index (BMI) is a widely used screening tool for categorizing weight status relative to height. While it does not directly measure body fat or distribution, it is a convenient and often effective indicator at the population level and for initial clinical assessment.
Calculation of BMI:
BMI is calculated using the following formulas:
- Using kilograms (kg) and meters (m): BMI = Weight (kg) / [Height (m)]² Example: A person weighing 70 kg with a height of 1.75 m has a BMI = 70 / (1.75 * 1.75) = 70 / 3.0625 ≈ 22.9 kg/m²
- Using pounds (lb) and inches (in): BMI = [Weight (lb) / Height (in)²] * 703 Example: A person weighing 150 lb with a height of 65 inches has a BMI = [150 / (65 * 65)] * 703 = [150 / 4225] * 703 ≈ 0.0355 * 703 ≈ 24.9 lb/in²
Classification of Weight Status using BMI (WHO standard for adults):
- Underweight: < 18.5 kg/m²
- Normal weight: 18.5 – 24.9 kg/m²
- Overweight: 25.0 – 29.9 kg/m²
- Obesity Class I: 30.0 – 34.9 kg/m²
- Obesity Class II: 35.0 – 39.9 kg/m² (often referred to as severe obesity)
- Obesity Class III: ≥ 40.0 kg/m² (often referred to as morbid obesity or severe, complex obesity)
Note on BMI Limitations: It is important to recognize that BMI is a screening tool and has limitations. It may overestimate body fat in individuals with high muscle mass (e.g., athletes) and underestimate it in older persons or others who have lost muscle mass. Ethnic variations in body composition and health risks at different BMI ranges also exist. Clinical assessment should always consider factors beyond BMI, such as waist circumference, body composition analysis, and the presence of comorbidities.
Eligibility for Bariatric Surgery based on BMI:
Generally, candidates for bariatric surgery typically meet one of the following criteria:
- BMI ≥ 40 kg/m² (Obesity Class III).
- BMI ≥ 35 kg/m² (Obesity Class II) with at least one significant obesity-related comorbidity (e.g., Type 2 Diabetes, severe sleep apnea, hypertension, dyslipidemia, NAFLD).
- In some guidelines and for specific patient populations (e.g., those with poorly controlled Type 2 Diabetes), surgery might be considered at a lower BMI (e.g., ≥ 30 kg/m² with comorbidities).
Beyond BMI, candidacy involves a comprehensive medical, psychological, and nutritional evaluation to ensure the patient is suitable for surgery, understands the risks and benefits, and is committed to the necessary lifelong lifestyle changes and follow-up care.
Types of Bariatric Surgery
Bariatric procedures work through various mechanisms, including restriction (limiting the amount of food the stomach can hold), malabsorption (reducing calorie and nutrient absorption in the small intestine), or a combination of both. Many procedures also induce favorable hormonal changes that affect satiety, hunger, and glucose metabolism (metabolic effects). The choice of procedure depends on various factors, including the patient’s BMI, health status, comorbidities, eating habits, and the surgeon’s expertise.
Here are the most common types of bariatric surgery:
a) Roux-en-Y Gastric Bypass (RYGB)
- Description: This is one of the most common and well-established bariatric procedures. It involves creating a small stomach pouch (about the size of an egg) by dividing the upper part of the stomach. The jejunum (part of the small intestine) is then divided, and the lower portion is connected directly to the small stomach pouch (the “Roux limb”). The upper portion of the divided jejunum, carrying digestive enzymes and bile from the remaining stomach, duodenum, and upper small intestine, is reconnected further down the Roux limb (the “biliopancreatic limb”), forming a “Y” shape.
- Mechanism: RYGB is both restrictive (small pouch limits food intake) and malabsorptive (bypassing a significant portion of the small intestine reduces nutrient absorption). It also significantly alters the release of gut hormones, contributing to satiety and metabolic improvements.
- Advantages:
- Significant and sustained weight loss (typically 60-80% of excess weight).
- Excellent resolution or improvement of many comorbidities, particularly Type 2 Diabetes (often achieving remission).
- Proven, long-term results supported by extensive data.
- Less complex technically than BPD/DS.
- Disadvantages:
- More complex procedure than Sleeve Gastrectomy.
- Higher risk of nutritional deficiencies (vitamins, minerals like iron, B12, calcium, Vitamin D) due to malabsorption and bypassing parts of the intestine. Requires lifelong vitamin and mineral supplementation.
- Potential for Dumping Syndrome (rapid gastric emptying causing nausea, sweating, dizziness, diarrhea) with consumption of high-sugar foods.
- Permanent and not easily reversible.
- Internal hernias are a long-term risk.
- Potential Complications: Anastomotic leak (leakage at the connection points), bleeding, infection, strictures (narrowing at the connection points), marginal ulcers (ulcers where the pouch connects to the intestine), nutritional deficiencies (necessitating strict adherence to supplementation), internal hernias, gallstones (due to rapid weight loss), Dumping Syndrome.
b) Laparoscopic Sleeve Gastrectomy (LSG)
- Description: In this procedure, about 75-80% of the stomach is removed surgically, leaving behind a “sleeve” or tube-like structure. The portion removed includes the fundus of the stomach, which is the main site of production for Ghrelin, often called the “hunger hormone.”
- Mechanism: Primarily restrictive (smaller stomach limits food intake). Also has significant metabolic effects due to the removal of the fundus and changes in gastric emptying and gut hormone release. While less malabsorptive than RYGB or BPD/DS, changes in transit time can modestly affect absorption.
- Advantages:
- Significant weight loss (typically 50-70% of excess weight).
- Resolution or improvement of common comorbidities, including Type 2 Diabetes, hypertension, and sleep apnea.
- Technically simpler procedure than RYGB or BPD/DS.
- No intestinal bypass, potentially leading to fewer malabsorptive complications and generally easier nutritional management compared to RYGB or BPD/DS.
- No foreign body is implanted (unlike adjustable band).
- Lower incidence of Dumping Syndrome compared to RYGB.
- Disadvantages:
- Permanent and not reversible.
- Can potentially worsen or cause new onset of gastroesophageal reflux disease (GERD) in some patients.
- Less effective for managing complex Type 2 Diabetes compared to RYGB or BPD/DS in some patients.
- Weight loss may not be as significant as with RYGB or BPD/DS in the long term for some individuals.
- Potential Complications: Staple line leak (leakage along the cut edge of the stomach), bleeding, infection, stricture (narrowing of the sleeve), GERD/heartburn, nutritional deficiencies (though generally less severe than RYGB/BPD/DS, still require monitoring), vitamin B12 deficiency (less common than RYGB but possible), long-term weight regain is possible if dietary habits are not maintained.
c) Biliopancreatic Diversion with Duodenal Switch (BPD/DS)
- Description: This is a more complex procedure that involves two parts: first, a large portion of the stomach is removed, similar to a sleeve gastrectomy (but often leaving a slightly larger sleeve). Second, the small intestine is drastically rearranged. The duodenum (the first part of the small intestine) is divided, and the connection from the stomach sleeve is made to a much lower part of the small intestine (the “alimentary limb”). The section of the small intestine that carries bile and digestive juices (the “biliopancreatic limb”) is connected to the final segment of the small intestine (the common channel), very close to the large intestine. This leaves a very short segment of small intestine where food mixes with digestive juices for absorption.
- Mechanism: Highly restrictive (sleeve) and significantly malabsorptive (limiting the length of the common channel for nutrient absorption). It also has profound metabolic effects.
- Advantages:
- Highest amount of weight loss among common bariatric procedures (typically 70-90% of excess weight).
- Most effective procedure for the remission of Type 2 Diabetes.
- Excellent long-term weight maintenance results.
- Disadvantages:
- Highest complexity and risk profile compared to SG and RYGB.
- Highest risk of severe nutritional deficiencies (protein, fat-soluble vitamins A, D, E, K, and minerals like iron, calcium, zinc). Requires rigorous, lifelong, and often higher-dose vitamin and mineral supplementation and closer nutritional monitoring.
- Potential for chronic diarrhea, foul-smelling stools, and gas due to malabsorption.
- Increased risk of protein malnutrition.
- Longer hospital stay and recovery time compared to SG.
- Permanent and irreversible.
- Potential Complications: Anastomotic leak, bleeding, infection, stricture, marginal ulcers, severe and complex nutritional deficiencies (requiring diligent monitoring and supplementation), protein malnutrition, chronic diarrhea, Dercum’s disease (rare painful fat deposits), potential for small bowel obstruction, gallstones.
d) Adjustable Gastric Banding (AGB)
- Description: An inflatable silicone band is placed around the upper part of the stomach, creating a small pouch above the band with a narrow opening to the rest of the stomach. The band can be adjusted (inflated or deflated) by injecting or removing saline through a port placed under the skin.
- Mechanism: Primarily restrictive – the small pouch and narrow opening limit food intake and slow down the passage of food.
- Advantages:
- Least invasive procedure with no cutting or stapling of the stomach or intestines.
- Adjustable and potentially reversible.
- Lower initial complication rate compared to other surgeries.
- Disadvantages:
- Lowest amount of weight loss compared to SG, RYGB, and BPD/DS (typically 40-60% of excess weight).
- Higher rate of long-term complications specific to the device (erosion, slippage, port issues).
- Higher rate of weight regain or insufficient weight loss over time.
- Less effective in resolving comorbidities compared to other procedures.
- Can cause reflux, esophagitis, and esophageal dilatation.
- Requires frequent adjustments.
- Potential Complications: Band slippage or erosion into the stomach wall, port infection or complications, tubing kinking or breakage, esophageal dilatation, GERD, insufficient weight loss, weight regain, need for re-operation or conversion to another bariatric procedure. Note: Due to lower efficacy and device-specific complications, the use of AGB has significantly declined in many parts of the world.
Conclusion
Bariatric surgery is a powerful and effective therapeutic option for individuals suffering from severe obesity and its related comorbidities who have not achieved sufficient results with non-surgical methods. The choice of procedure is a complex decision involving a detailed assessment of the patient’s health status, weight loss goals, comorbidities, and potential risks. While highly effective in promoting significant and sustained weight loss and improving metabolic health, bariatric surgery is a major intervention requiring careful patient selection, comprehensive pre-operative preparation, skilled surgical execution, and, critically, lifelong commitment to dietary, lifestyle, and behavioral changes, as well as regular medical follow-up for nutritional monitoring and overall health management. It is part of a multidisciplinary approach involving surgeons, physicians, dietitians, psychologists, and other healthcare professionals focused on long-term patient success and well-being.
