What’s new in weight loss management and surgery?

Obesity: a rising burden of disease

Obesity (defined as a body mass index [BMI] of >30 kg/m²) is a polymorphic chronic disease that has increased in both incidence and prevalence throughout the 20th and 21st centuries.¹ It has reached epidemic proportions and is now one of the most important public health issues globally.² 

Body weight and fat mass are highly heritable traits, with important genetic and epigenetic aetiological factors.³ The rise in the prevalence of obesity has largely been driven by environmental factors including an abundance of calorie-rich food and a lack of physical activity.⁴ An estimated 603.7 million adults worldwide were obese in 2015 and it is predicted that without significant action approximately 223 million children will have excess weight by 2025.^5,6

The incidence of comorbidities that have obesity as a strong contributory factor and are responsible for a large public health burden have risen along with those of obesity. These comorbidities include type 2 diabetes, cardiovascular disease (e.g. coronary heart disease, cerebrovascular disease), musculoskeletal disorders (e.g. osteoarthritis) and cancers with an aetiological association with obesity (e.g. oesophageal adenocarcinoma and some breast, ovarian, prostate, liver, colon and renal cancers).⁷

The challenge of treating obesity requires a commitment from the patient to lifelong permanent changes in eating and activity behaviours. Achieving this involves combinations of low-calorie diets, exercise programs, pharmacotherapy and, in some patients, bariatric surgery.

Medical therapy

Pharmacotherapy has an adjuvant role to diet and exercise and may be helpful to kick start weight loss and aid appetite suppression. Pharmacotherapy adjuncts for weight loss date back to the 1920s and agents such as phentermine have been used since the 1950s.⁸ Newer formulations offer greater flexibility of dosing and there are now new combinations of drugs, some of which have yet to be made available in Australia. Liraglutide, which was first used to treat diabetes, is thought to centrally exploit the hypothalamic target for appetite suppression and delay gastric emptying. Combination therapies include phentermine and topiramate (not approved for use in Australia), which combines a weight loss drug with an antiepileptic drug for a greater weight loss effect but tolerability limits its use.⁹ 

Pharmacotherapies used in weight loss management and their mechanisms of action are listed in Table 1. Patient responses to these therapies are variable for clinically meaningful weight loss (more than 5% body weight loss after 12 weeks of therapy). 

Surgical intervention

At a patient management and therapeutic level, bariatric surgery (also known as weight loss surgery) is increasingly being relied on as the most effective way to enable significant durable weight loss in severely obese patients who fail genuine efforts with dietary, exercise and lifestyle measures. The review of surgical interventions for the treatment of obesity from the Australian Government Department of Health supports this approach.¹⁰ The new term ‘metabolic surgery’ more appropriately recognises the physiological benefits of these procedures (chief among them, reversal of diabetes risk).¹¹

Bariatric operations have traditionally been categorised according to the mechanism by which weight loss ensues:

• restrictive procedures (limit intake)
• malabsorptive procedures (interfere with digestion and absorption)
• combination of the above procedures.

Selection of patients for bariatric surgery

Although some patients have success with early intervention and modifications to diet and lifestyle, many will be unable to achieve adequate sustained weight loss. The National Health and Medical Research Council guidelines state that obese patients can be selected for bariatric surgery if they have failed sustained efforts with dietary and lifestyle therapies.¹² Bariatric surgery should be discussed with motivated patients who have a BMI of 35kg/m² or greater and one or more obesity-associated comorbidity. Reflecting the low success rates with nonsurgical approaches, bariatric surgery can also be considered in patients with morbid obesity (BMI >40kg/m²) even in the apparent absence of obesity-related comorbid disease. The indications and contraindications for bariatric surgery are listed in Box 1.

The GP’s role 

Work up by the GP is essential for obese patients who are considering bariatric surgery (Box 2).¹³ Failed dietary and lifestyle management is the impetus to surgical referral. It is accepted that three to six months of lifestyle change be trialled before putting patients forward as candidates for surgical management. During this time, an assessment of the patient’s level of motivation to adopt major lifestyle changes can be made. A realistic and sustainable diet plan should be implemented rather than a ‘fad’ diet. Patients are likely to seek advice from their GP regarding suitability, operation selection and risk of complications. They have often discussed the procedure with others who have undergone weight loss surgery and have also performed online research. Patients need to be made aware that there is not yet evidence to support some novel techniques such as gastric aspiration devices. An outline of the different operations available should be given to patients, with a discussion of the risks, potential complications and expected benefits. The patient should also be informed of the necessary postoperative diet and lifestyle changes. Subsequent discussions with a bariatric surgeon will provide more detailed information regarding operative issues.

An upper gastrointestinal endoscopy is performed before surgery, primarily to identify a hiatus hernia, which requires repair at the time of bariatric surgery to reduce the risk of gastro-oesophageal reflux disease. Endoscopy is also required to exclude Barrett’s oesophagus. Preoperative assessment by the anaesthetist may require specific cardiac or respiratory tests. 

Surgical options and current trends

In 2014-15, an estimated 22,700 weight loss surgical procedures were performed in Australia, an increase from 9300 in 2005-06 according to a Australian Institute of Health and Welfare report.¹⁴ More than 90% were performed in the private sector highlighting the lack of government recognition for access in the public sector. Robotic bariatric surgery is proven equivalent but not superior to other types of minimally invasive bariatric surgery and comes at a higher cost.¹⁵ Biliopancreatic diversion with duodenal switch is not discussed in this article as the procedure is rarely used in Australia.

Sleeve gastrectomy

Sleeve gastrectomy is an operation that is usually performed laparoscopically. In most patients 70 to 80% of the stomach is removed by stapling parallel to the lesser curvature in a cephalad direction (Figure 1a). The pylorus is preserved, which reduces the risk and severity of dumping syndrome. As well as greatly reducing the gastric volume, several metabolic and hormonal changes ensue. These include reduced levels of ghrelin (the hunger peptide), glucagon, glucagon-like peptide 1 and leptin.¹⁶ Initial weight loss is swift and sustained with only minor weight gain after several years in most patients.¹⁷ 

The major complications of sleeve gastrectomy are staple line leak or bleed in the immediate postoperative period and gastro-oesophageal reflux as a later problem. Sleeve gastrectomy has become the dominant operation type in most western countries including Australia and the USA.¹⁸ The reason for this is that it is more reliably effective than gastric band surgery, which was previously the most frequently performed operation but is now far less commonly performed. Sleeve gastrectomy has very similar effectiveness to Roux-en-Y gastric bypass (RYGB), with both operations providing more than 70% excess weight loss in a randomised trial.¹⁷ It is however significantly safer than the RYGB operation and avoids the long-term complications of the bypass operation.^18,19 

Laparoscopic adjustable gastric band

Following the first successful laparoscopic placement of an adjustable gastric band in 1995, uptake rates were high and promising initial results were reported (Figure 1b). Over time, laparoscopic adjustable gastric band (LAGB) procedure has fallen out of favour because of problems with obstruction due to ingested food being stuck at the narrow lumen of the band, gastro-oesophageal reflux, which can be severe, and other complications including band slippage, band erosion, port/tubing problems and long-term failure of weight loss (up to 62% of patients in some series).²⁰

Roux-en-Y gastric bypass 

RYGB is the most technically demanding and metabolically disruptive of the bariatric procedures. This operation results in gastric restriction and intestinal malabsorption. The procedure involves restricting the size of the stomach by stapling off 90% of the lower stomach creating a small pouch; the bypassed stomach remains in situ and is subsequently difficult to examine endoscopically. A Roux alimentary limb of jejunum is anastomosed to the gastric pouch, with the biliopancreatic juice entering the bowel 40cm or lower at a second anastomosis (Figure 1c). Malabsorption is therefore induced by bypassing normal absorption of ingested food in the foregut.  Complications include anastomotic leak, internal herniation, bowel obstruction and nutritional problems due to the malabsorption. Despite the higher morbidity and mortality profile of RYGB compared with either sleeve gastrectomy or LAGB, gastric bypass should be considered in some patients, such as those with markedly severe obesity, significant gastro-oesophageal reflux disease, especially with Barrett’s disease, and those with severe type 2 diabetes.

Follow up after surgery

In the early postoperative phase, patient progress is monitored closely with dietitian input. Patients progress from a fluid-only diet, to puree and soft food, and eventually to a relatively normal diet in most over the course of two to four weeks. Some patients report permanent inability to tolerate some foods such as steak or bread, especially in those who have undergone LAGB surgery. It is important that patients remain well hydrated and that protein intake is 60 to 80g/day, for which commercially formulated liquid very low-calorie diet meals are useful. 

Deficiencies of many micro and macronutrients can occur postsurgery and should be monitored for. The most common deficiencies and those patients most at risk are listed in Table 2. A typical set of blood tests for a patient undergoing sleeve gastrectomy at six months, 12 months and annually thereafter includes full blood count and measurement of albumin,  calcium, magnesium, phosphate, folate, parathyroid hormone, 25-hydroxy vitamin D, iron, transferrin and vitamin B₁₂ levels.

Novel antiobesity procedures

It is important for GPs to be able to inform their patients that novel devices for obesity, outlined below, are neither restrictive (in the sense of decreasing oral intake) nor malabsorptive. Also, they go against the bariatric principles of healthy eating choices and modifications to diet that are at the premise of weight loss management.

Intragastric balloons

Some patients who are unwilling to undergo surgery opt to have endoscopic placement of an intragastric balloon. The saline filled silicone balloon within the stomach mimics gastric fullness. The treatment is temporary (six months) but may be repeated at intervals. Initial weight loss should occur when used in concert with lifestyle changes but weight regain is reported to occur in approximately one-third of patients after balloon removal and weight cycling between serial procedures is common.²¹ Complications include pain, nausea, halitosis and in the longer term gastric erosion or ulceration. The balloon may also deflate and migrate, causing a bowel obstruction. Currently peer- reviewed and published evidence in the literature is inadequate to establish the safety and efficacy of this procedure.

Endoscopic sleeve gastroplasty

Endoscopic sleeve gastroplasty (e.g. transoral gastroplasty) uses flexible staplers introduced through the mouth and oesophagus to create a narrow gastric lumen that is intended to replicate a now discarded operation, vertical banded gastroplasty. The long-term failure of that operation suggests that results will need to be monitored for failure of the suture line after endoscopic gastroplasty. Intake is restricted and satiety following small meals occurs. Professional societies such as the American Society for Gastrointestinal Endoscopy suggest that endoscopists performing these procedures have a system in place for enrolment and long-term  follow up of these patients to monitor weight loss and maintenance.

Conclusion

In obese patients who have comorbidities such as type 2 diabetes, bariatric surgery has been demonstrated to be superior to intensive medical therapy in managing these diseases.¹¹ Most patients will achieve apparent full remission of comorbid disease, including type 2 diabetes, but the disease can recur if weight is regained. Bariatric surgical management has been shown to reduce all-cause mortality (including deaths due to diabetes, cardiovascular disease and cancer) in obese patients.^22-27 It represents a growing area of experience for patient care, with good evidence to support certain bariatric techniques for sustained weight loss and improvements in overall health.  An experienced team approach, tailoring treatment to the individual patient is important. If surgery is appropriate, the risks and  benefits for each patient, including the psychological effects of permanent inability to eat a normal-sized meal, need to be considered and explained. At present sleeve gastrectomy has the best risk-to-benefit profile. Patients must commit to lifelong adherence to dietary modifications and vitamin monitoring, as deficiencies are common. 

Overall, obesity is a complex disease for which specialist weight assessment and management clinics are required for optimal care. With the emergence of new drugs, devices and surgical procedures, as well as ever increasing patient numbers, assessment by teams skilled in this area is becoming more necessary. Surgery has a definitive effective role in management. Postsurgery diligent follow up and review of patient care is essential to maintain weight loss and remission of comorbid disease. MT

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