In the UK, the incidence of obesity and associated comorbidities continues to increase (Health and Social Care Information Centre, 2014). Recent studies have shown that intensive medical therapy with bariatric surgery is a more effective way at regaining glycaemic control, reducing weight and then sustaining weight loss than intensive medical therapy alone (Schauer et al, 2014).
The aims of bariatric surgery are to reduce weight, reduce medical problems and prevent onset of weight-related medical conditions. Procedures can be temporary or permanent and can work by either restricting food intake, reducing the amount of food absorbed, or a mixture of both. The most common bariatric surgery procedures performed in the UK include gastric banding, Roux-en-Y bypass (gastric bypass), sleeve gastrectomy and biliopancreatic diversion ([BPD] with or without duodenal switch). These procedures are usually performed laparoscopically. There are weight loss interventions that can be completed less invasively; for example, intragastric balloon procedures are carried out endoscopically. The intragastric balloon is a temporary procedure that is often used before bariatric surgery to “kickstart” weight loss. It is not usually funded by the NHS, except in extreme conditions.
Most studies have indicated that gastric bypass and sleeve gastrectomy are more effective at achieving weight loss than gastric banding (Tice et al, 2008; Farrell et al, 2009). However, although not consistently reported, a resolution of obesity-related comorbidities can be achieved with most bariatric procedures. The three most common procedures have acceptable efficacy and safety, with gastric banding seeming to be a safer procedure with frequent, but less severe, long-term complications (Franco et al, 2011).
Patient criteria for bariatric surgery varies between hospitals, public and private hospitals and countries. In the UK, NICE (2014) recommends that bariatric surgery should be considered if:
- An individual has a BMI of 40 kg/m2 or more, or between 35 kg/m2 and 40 kg/m2 and other significant diseases (for example, type 2 diabetes or high blood pressure) that could be improved by weight loss.
- All appropriate non-surgical measures have been tried but the person has not achieved or maintained adequate, clinically beneficial weight loss.
- The person has tried to lose weight by making lifestyle changes for at least 6 months, but they have not lost any weight.
- The person has been receiving or will receive intensive management in a tier 3 service.
- The person is generally fit for anaesthesia and surgery.
- The person commits to the need for long-term follow-up.
- Other treatment options have failed among people with a BMI of over 50 kg/m2.
Bariatric surgery is not always suitable even if the above criteria are met in the following situations:
- Life-threatening illnesses, which includes terminal cancers, liver failure and heart failure.
- Untreated eating disorders.
- Untreated or severe psychiatric illness.
- Genetic conditions that are linked to increased weight. However, studies have suggested that bariatric surgery is a viable option for people with Prader-Willi syndrome (Alqahtani et al, 2015).
Once bariatric surgery is deemed appropriate by the multidisciplinary team with experience in preoperative care, counselling and management (Mechanick et al, 2008), surgery can be commenced. As part of the preoperative care, blood tests should be carried out, and any nutritional deficiencies identified at this time should be addressed (Heber et al, 2010). Box 1 provides a summary of the essential blood tests that should be performed prior to bariatric surgery. Additional tests (e.g. pregnancy or thyroid function tests) may be required according to individual needs (O’Kane et al, 2014).
Complications following bariatric surgery
Complications following bariatric surgery are rare, and even more so when procedures are conducted laparoscopically as apposed to open procedures. Obesity and its comorbid conditions increase the risk of complications while anaesthesia is also more difficult in this group of people (Schumann, 2013). Peri-operative mortality is less than 0.3% for bariatric surgery, and this is declining with increasing experience of surgeons and their multidisciplinary team (Kim and Wolfe, 2012). The incidence of complications also varies with the frequency of follow up and the level of engagement of patients with the multidisciplinary team. Box 2 lists some of the complications that can occur following bariatric surgery, with some described in more detail below.
Dumping syndrome is a debilitating complication of gastrointestinal and vasomotor symptoms that present postprandially due to rapid gastric emptying (Berg and McCallum, 2015). One cause of dumping syndrome is gastric surgery, and among adults, gastric bypass surgery is the most common cause, with the incidence of dumping syndrome as high as 75% (Abell and Minocha, 2006). Dumping syndrome after a sleeve gastrectomy is less frequent (Berg and McCallum, 2015).
Following gastric bypass, dumping syndrome develops after high-sugar and high-fat foods are eaten but remain undigested due to the artificially made smaller stomach. This leads to an osmotic overload once delivered to the small intestine. Fluid is drawn into the intestinal lumen by osmosis stimulating a vagal reaction (Fujioka, 2005), which leads to symptoms of abdominal pain, sweating, nausea, diarrhoea, flushing, tachycardia and syncope (Heber et al, 2010). Changes to diet such as having smaller and more frequent meals, separating “dry” and “wet” foods (as liquids speed gastric emptying) and eating fibre and complex carbohydrates can alleviate some of the symptoms. For a medicinal treatment, acarbose can be prescribed in late dumping syndrome (symptoms appear 1–3 hours postprandially) because it interferes with the digestion of polysaccharides to monosaccharide (De Cunto et al, 2011). Octreotide alleviates both early (symptoms appear within 30 minutes postprandial) and late dumping syndrome symptoms through inhibition of the hormones that encourage digestion (Didden et al, 2006).
All types of bariatric surgery lead to very reduced total calorie intake, especially in the first 6 months after surgery; therefore, it is common that people who have undergone bariatric surgery will develop some degree of nutritional deficiency. It is necessary to screen patients on a regular basis for nutritional deficiencies and personalise supplementation to avoid deficiencies and complications (see Table 1). Best practice guidelines recommend lifelong daily multivitamin and calcium supplementation with added vitamin D (Heber et al, 2010). Investigations for people who have bariatric surgery will depend on the type of surgery and symptoms experienced by patients (Table 2). Deficiencies are less common in patients who have undergone gastric balloon and gastric banding compared with malabsorptive procedures like gastric bypass and biliopancreatic diversion (Xanthakos and Inge, 2006; Gracia et al, 2007).
Metabolic bone disease
Metabolic bone disease (MBD) develops in some patients following bariatric surgery, due to reduced absorption of calcium and vitamin D from the duodenum and proximal jejunum (Sanghera et al, 2012). It was believed that MBD was more common in malabsorptive procedures; however, exclusively restrictive procedures have been shown to put patients at risk of MBD (Pugnale et al, 2003).
Weight loss of 10% for an obese or overweight person, whether it is achieved by bariatric surgery or not, can accelerate bone loss and result in approximately 1–2% bone loss (Williams, 2011).
Deficiency of calcium and vitamin D as a result of bariatric surgery results in an elevation of parathyroid hormone (PTH), also known as secondary hyperparathyroidism (excessive secretion of PTH by the parathyroid glands in response to low blood calcium levels). Increased PTH increases bone turnover and bone resorption. Patients with MBD can present with bone and joint pain, muscle weakness and, occasionally, bone fractures (Sanghera et al, 2012).
Therefore, all patients who have received bariatric surgery should undergo routine screening for MBD. Monitoring includes measuring calcium, PTH and vitamin D levels every 6 months for the first 2 years and annually thereafter. To quantify bone mineral density, dual-energy X-ray absorptiometry (DEXA) scanning is recommended every 2 years until bone mineral density is stable (Heber et al, 2010). The management and avoidance of MBD involves vitamin D and calcium supplements, and bariatric individuals should also be encouraged to increase weight bearing activity (Aills et al, 2008). If osteoporosis is found on a DEXA scan parenteral bisphosphonates may be considered, only after appropriate therapy for calcium and vitamin D insufficiency, as oral preparations are not well absorbed in people who have had malabsorptive procedures (Mechanick et al, 2013).
Weight regain after bariatric surgery
Weight regain is a fairly common occurrence after bariatric surgery, and it can be expected that 20–25% of the lost weight will be regained over a period of 10 years (Heber et al, 2010). In the author’s experience, weight regain is more often seen following gastric banding surgery and occasionally with gastric bypass and biliopancreatic diversion. The causes of weight regain include the following:
- Non-compliance with dietary and lifestyle restrictions.
- Non-attendance at follow-up clinic.
- Insulin use.
- Surgical failure.
- Physiological factors (Heber et al, 2010).
Interestingly, food records show that calorie intake is reduced after bariatric surgery, but increases at 1–2 years after surgery coincide with weight regain (Sjöström et al, 2004). As bariatric patients can begin to disengage with the post-bariatric care and become non-compliant, it is imperative that the multidisciplinary team are aware of the factors that might contribute to weight regain, and that patients are educated during their follow-up period and assessed for any of these factors. Patients should also be given realistic preoperative expectations of the results of the bariatric surgery.
Excess, redundant skin
An unwelcome outcome of bariatric surgery can be excess, redundant skin as a result of rapid massive weight loss. Excess skin confers an increased risk of medical problems, such as fungal infections and eczema, and also psychocosmetic problems such as depression (Song et al, 2006) and body dissatisfaction (Mitchell et al, 2008). Patients may feel unattractive and embarrassed by their appearance (Staalesen et al, 2013; Biörserud et al, 2015).
Body-contouring surgery is an option to remove excess skin. In England, there is no standardised guidance for the provision of body contouring following massive weight loss (British Association of Plastic and Reconstructive and Aesthetic Surgeons, 2014). It is funded by the NHS in exceptional medical circumstances and availability across the UK is not consistent (Mukherjee et al, 2014).
Pregnancy and bariatric surgery
Women who have had bariatric surgery are often advised to avoid pregnancy for the first 12 to 18 months after surgery (Mechanick et al, 2008). This is to ensure that women of child-bearing age have stabilised in weight and metabolic status after surgery. Pregnant women are advised to take 400 µg daily of folic acid until the 12th week of pregnancy to reduce the risk of neural tube defects in the fetus (NICE, 2008). For women with obesity or diabetes, 5 mg of folic acid daily is recommended until the 13th week of pregnancy (Centre for Maternal and Child Enquiries/Royal College of Obstetricians and Gynaecologist [CMACE/RCOG], 2010). This is available on prescription and should ideally be taken up to a month before conception.
Women who have had surgery and are planning to conceive are advised to avoid vitamin and mineral preparations that contain vitamin A in the retinol form in the first 12 weeks of pregnancy. Supplements containing vitamin A may increase the teratogenic risk and hence vitamin and mineral supplements containing no vitamin A, which are specifically aimed at preconception and pregnancy, or taking vitamin A in the beta-carotene form are recommended (NICE, 2008).
Women who become pregnant following bariatric surgery should also have regular follow-up by their multidisciplinary bariatric team every trimester. Pregnant women, especially those who have had distal gastric bypass or biliopancreatic diversion, may be at risk of low vitamin A levels and should be monitored closely during pregnancy. A more frequent review with the specialist bariatric dietitian may be required if they have any complications or deficiencies.
Diabetes and bariatric surgery
Remission of type 2 diabetes (defined as an HbA1c less than 48 mmol/mol [6.5%] when not using hypoglycaemic therapy) is sometimes observed following weight loss surgery and the rate of remission is highest among patients who have undergone biliopancreatic diversion, followed by gastric bypass and then sleeve gastrectomy (Sjöström et al, 2004; Sjöström, 2013). Remission is more likely to be encountered if the duration of diabetes is less than 10 years and patients are not on insulin prior to surgery. Severely obese people with type 1 diabetes who have undergone gastric bypass surgery have shown improved metabolic control and a reduced insulin requirement (Czupryniak et al, 2004). Remission of type 2 diabetes after surgery is hypothesised to be due to:
- An increase in glucagon-like peptide-1 response to a meal following surgically induced direct delivery of nutrients to the small intestine.
- Induction of sudden negative calorie balance by reduction in the food absorbed following surgery (Knop and Taylor, 2013).
With remission of type 2 diabetes or improvement in glycaemic control, most patients will not need to continue taking glucose-lowering medication. It is common for insulin to be discontinued immediately after surgery along with other oral medications for diabetes; however, in the author’s experience, it is prudent to continue with standard preparation of metformin if it can be tolerated. Patients should be monitored for relapse of diabetes on a regular basis with at least yearly monitoring of HbA1c.
With the increase in incidence of obesity and diabetes, and the likely increase in bariatric procedures, clinicians should be aware of the key aspects of post-bariatric care. Every institution undertaking bariatric surgery should have a multidisciplinary team and a clear follow up and educational programme after weight loss surgery.