Obesity is a complex metabolic disease affecting 400mn people worldwide and is a major health problem that contributes to many life threatening and disabling diseases including type-2 diabetes mellitus, hypertension, ischemic heart disease, osteoarthritis, obstructive sleep apnea, gastroesophageal reflux disease, non alcoholic steatotic hepatitis, polycystic ovarian syndrome, certain cancers and all-cause mortality.
Obesity usually is classified by body mass index (BMI), calculated as body weight in kilograms divided by height in metres squared (kg/m²). This classification is based on associations with adverse health consequences, with a BMI of 25 to 29.9 kg/m², 30 to 34.9 kg/m², 35 to 39.9 kg/m², and 40 kg/m² or higher corresponding to overweight, class I (mild), class II (moderate), and class III (severe, morbid) obesity, respectively.
Currently, 69.2% of adults older than the age of 20 years in the United States are overweight or obese and 6.3% categorised as class III obesity. Furthermore, class III obesity is the fastest growing obesity subgroup because its prevalence is increasing twice as quickly as lesser degrees of obesity.
About 75% of Qataris are overweight and 40% are obese or morbidly obese, according to the latest figures from the National Health Strategy 2011-2016. According to the International Diabetes Federation (IDF) Diabetes atlas 2012 report, about 23.3% of the Qatar’s overall adult population suffers from diabetes; in comparison, only about 8.3% of the adult population worldwide is diabetic. Qatar ranks 8th highest prevalence of diabetes in the world and the 3rd highest in the GCC, next to Kuwait and Saudi Arabia.
The long-term results of traditional weight loss therapies, including diet, exercise, and medications, are relatively poor. Bariatric surgery or metabolic surgery is the most effective treatment of morbidly obese patients to allow substantial, sustained weight loss and to improve or resolve obesity-associated comorbidities, thereby reducing mortality.
Eligibility criteria for bariatric surgery
There are a range of guidelines regulating eligibility for bariatric surgery that share the common concept that all candidates must have failed in undertaking conservative weight loss measures and shown a commitment to long-term follow-up evaluation. Indications for bariatric surgery are:
m BMI greater than or equal to 40 kg/m² or BMI greater than or equal to 35 kg/m² with obesity-related comorbidities
m Age between 16 and 65 years
m Acceptable surgical/medical risk
m Failure of effective and lasting weight loss with appropriate nonsurgical treatment
m Psychological stability
m A well-informed and motivated patient with realistic expectations
m Commitment to prolonged lifestyle change and long-term follow-up evaluation
m Supportive family and social environment
m Resolution of alcohol or substance abuse
m Absence of active psychosis and untreated severe depression
Bariatric surgical procedures
All bariatric procedures are categorised as restrictive, malabsorptive or a combination of the two. This classification is based on the assumption that bariatric surgery influences only food intake and/or nutrient absorption without taking into account the more recent findings of the hormonal and metabolic effects of these procedures.
According to the traditional view, restrictive procedures involving gastric restriction, such as LAGB (Laparoscopic Adjustable Gastric Banding) and SG (Sleeve Gastrectomy), cause early satiety during meals by decreasing the volume of the stomach.
Malabsorptive procedures, such as BPD/DS (Laparoscopic Biliopancreatic Diversion with Duodenal Switch), rely on the bypass of various lengths of the small intestine, thereby effectively reducing nutrient absorption. Mixed procedures, such as RYGB (Laparoscopic Roux-en-Y Gastric Bypass), combine gastric restriction with bypass of a short segment of the small bowel.
Laparoscopic Adjustable Gastric Banding:
In LAGB, a silicon band is applied around the stomach just below the gastro-oesophageal junction, and is tightened through a subcutaneous access port by the injection or withdrawal of a saline solution, allowing for adjustment of the cuff size by saline injection. The mechanism of action of LAGB is the induction of early and prolonged satiety.
Laparoscopic Sleeve Gastrectomy
In LSG the stomach is transected vertically creating a high-pressure gastrictube and leaving a pouch of up to 200ml. In addition to restricting the stomach capacity thereby reducing the food intake, resection of the gastric fundus also removes ghrelin-producing cells, a hormone mediating appetite, subsequently reducing appetite. The popularity of LSG relies on its technical simplicity and avoidance of frequent complications associated with laparoscopic RYGB (LRYGB) and BPD/DS.
Laparoscopic Roux-en-Y Gastric Bypass (LRYG)
In the mid-1990s, LRYG has become the gold standard and most commonly performed bariatric surgery in the United States. The proximal stomach is transected to create a 15- to 20-ml pouch. The jejunum is divided and the distal alimentary Rouxlimb is connected to the stomach pouch. The proximal biliopancreatic limb then typically is joined with the alimentary limb. Besides restriction of food intake by decreasing the stomach size and mild impairment of nutrient absorption, changes in the production of gastrointestinal hormones as a consequence of the rearranged gut recently have been implicated in the explanation of weight loss and remission of comorbidities.
Laparoscopic Biliopancreatic Diversion With Duodenal Switch
The first step is a sleeve gastrectomy, creating a gastric tube with a volume of 150 to 250ml. Next, the small bowel is divided and the biliary limb is anastomosed to the common channel 100cm proximal to the ileocecal valve. The distal small bowel then is anastomosed to the duodenum.
Because of its long term risk of severe nutritional deficiencies without proper long-term follow-up evaluation and care, this surgery now is reserved for patients with a BMI greater than 50 kg/m2.
Outcomes after bariatric surgery
The primary goal of bariatric surgery is to achieve substantial sustained weight loss that is adequate to decrease obesity-related comorbidities, thereby ameliorating health, quality of life, and long-term survival. EWL (excess weight loss) is derived from the following formula: percentage of EWL = (weight loss/excess weight) ×100, where excess weight equals total preoperative weight minus ideal weight. EWL reported in in 2004 were AGB: 47.5%, RYGB: 61.6% and BPD: 70.1%.
In 2009, a review and meta-analysis involving 135,246 patients showed that overall 78.1% of diabetic patients had complete resolution and diabetes was improved or resolved in 86.6% of patients. Weight loss and diabetes resolution were greatest for patients undergoing biliopancreatic diversion/ duodenal switch, followed by RYGB, and finally LAGB.
Patients with greatly uncontrolled blood sugars with high baseline HbA1c >10% (<7% indicates good control) have a lower rate of remission compared with those with a lower HbA1c (6.5–7.9). Also, a pre-operative duration of type 2 diabetes greater than 10 years was shown to significantly reduce the chances of remission. A shorter duration and better control of diabetes prior to surgery corresponds to a higher rate of remission.
Consequently, early surgical intervention in the morbidly obese diabetic patient is preferred by many bariatric surgeons.
Cardiovascular risk factors and mortality
Arterial hypertension often is associated with obesity and 40% to 70% of bariatric surgery patients are hypertensive. This combination of diseases increases the risk for cardiovascular disease, which has been shown to decrease substantially after substantial weight reduction following bariatric surgery. Resolution rates of hypertension showed some variation among studies depending on the respective bariatric procedure, with resolution rates greater than 68% for BPD/DS, 65% to 90.7% for RYGB, 78% to 93.8% for LSG, and 48% to 63% for LAGB.
Up to 50% of bariatric surgery patients with morbid obesity have high blood cholesterol, which is a major modifiable risk factor in atherosclerosis and coronary artery disease development. BPD is the most effective bariatric procedure in resolving dyslipidemia, especially in super obese patients (BMI>50 kg/m2).
Also, it was recently reported that bariatric surgery resulted in a significantly reduced number of cardiovascular deaths and a significantly lower number of total first-time cardiovascular events (ie, myocardial infarction or stroke), in comparison with conventional treatment.
Other benefits include reduction in rates of pulmonary disorders including obstructive sleep apnea and chronic obstructive pulmonary disease, improvement in acid reflux after RYGB, improvement of fatty liver disease and reduced incidence of some cancers.
Harmful effects of bariatric surgery
Despite the beneficial effects of bariatric surgery, it has been reported that 8.5% of patients developed acute kidney injury after RYGB. RYGB and BPD/DS have been shown to increase the risk of kidney stone disease. Also, there are concerns of specific procedure-related complications and vitamin, iron and mineral deficiencies associated with malabsorptive procedures.
Procedure selection in bariatric surgery
There are no definitive criteria for choosing one bariatric procedure over another. Patient factors such as BMI, age, sex, comorbidities, significant hiatal hernia, gastro-esophageal reflux disease, patient expectations, and surgical history play a role in determining which procedure is suitable. The surgeries vary substantially in their postoperative amount of weight loss, resolution of comorbidities, nutritional requirements, and nature and severity of complications. The expected durable weight loss and comorbidity resolution increases in the following order of procedures: AGB, SG, RYGB, and BPD/DS. The same holds true for the technical complexity and risk of complications together with the long-term risk of nutrient deficiencies.
Bariatric surgery is the best treatment option for morbid and complex obesity, complementing other therapies for weight management and obesity-related comorbidities. Beyond achieving substantial and durable weight loss, bariatric surgery improves metabolism far beyond lifestyle modifications and medical treatment alone.
The established surgeries are not only effective but also are safe. The 0.3% mortality rate is equivalent to those of several common abdominal surgeries, such as laparoscopic cholecystectomy.
Because each bariatric procedure has its own inherent risks and benefits, the choice of surgery depends on surgeon and patient preference, degree of obesity, and estimates of the quantity of weight loss needed to improve comorbidities substantially.
l Dr Nisar C Abdulla is a Specialist Internist at Aster Medical Center, C-Ring Road, Doha.